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Evaluation of Playing Surface Characteristics of Various In-Filled Systems

Evaluation of playing surface characteristics of in-filled systems.

Updated:

November 10, 2016

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Evaluation of Playing Surface Characteristics of Various In-Filled Systems

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by Andrew S. McNitt, The Pennsylvania State University
Dianne Petrunak, The Pennsylvania State University

Note

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Introduction and Objectives

Since synthetic turf was first installed in the Houston Astrodome in 1966, numerous studies have been conducted to evaluate the safety and playability of synthetic surfaces. These studies have included material tests on the traction and hardness of these surfaces (Valiant, 1990; Martin, 1990), human subject tests where an athlete performs various maneuvers on the surface (Cole et al., 1995; Nigg, 1997; Nigg and Segesser, 1988), and epidemiological studies that have counted athlete injuries on synthetic versus natural turfgrass (Powell and Schootman, 1992; Powell and Schootman, 1993).

Various methods have been developed to measure the playing surface quality of sports surfaces. For example, different methods of measuring playing surface hardness have been developed for synthetic turf versus natural turfgrass surfaces. For synthetic turf surfaces the U.S.A. standard is the F355 method (American Society for Testing and Materials, 2000a). For natural turfgrass the standard method is the Clegg Impact Soil Tester (CIST) (American Society for Testing and Materials, 2000b). Although both methods determine hardness by dropping a weighted accelerometer on the turf surface, some have stated that these two methods should not be correlated (Popke, 2002).

A new configuration of synthetic turf has been introduced into the market place. Termed 'infill' systems, these synthetic surfaces are comprised of a horizontal backing supporting numerous vertical nylon, polypropylene, or polyethylene fibers. These vertical fibers (pile) are much longer than those of traditional synthetic turf and can be filled with varying types of granulated material (infill media), typically sand or crumb rubber. It is believed that these new infill systems provide athletes with a surface that performs more like natural turfgrass than traditional synthetic turf (Popke, 2002).

As more synthetic turf systems using infill are introduced into the sports surface market, independent data regarding playing surface quality are required to enable consumers to make informed decisions.

Athlete Performance and Safety

A brief review of Athlete Performance and Safety of Infilled Synthetic Turf Systems.

Objectives

This study was designed to evaluate the playing surface quality of various infill systems over time. Surface quality will be periodically evaluated as the systems are exposed to weather and simulated foot traffic. The effects of various maintenance practices on the playing surface quality of these systems will also be evaluated.

Construction of Experimental Plot Area

In the fall of 2002, we prepared the sub-base for the installation of the infill systems.

The topsoil was stripped from the site and the subsoil was compacted (Fig 1).

A 4 in. layer of gravel (Fig. 2) was installed.

After the gravel was graded and compacted, a 0.75 in. layer of a fine gravel containing appreciable coarse sand (Fig. 3) was topdressed over the area

This allowed a more precise grade to be created (Fig. 4).

When the sub-base was complete, various companies marketing and installing infilled synthetic turf systems arrived at The Joeseph Valentine Turfgrass Research Facility at Penn State, and began installing their systems. Most installed nailers around the perimeter of their plots (Fig. 5).

Each product was installed in three 15 ft by 15 ft plots in random locations. All measurements and data reported in this document are the average of values obtained from the three locations (Fig. 6).

Some companies installed a shock-absorbing pad and some did not (Fig. 7). The three systems containing pads were: Astroplay, Nexturf, and Sofsport.

One company, Geoturf, installed an underlying grid that can be used to circulate heated or cooled air throughout the system (Fig. 8). No forced air circulation was done during this study but the effect of the underlying grid on playing surface characteristics was of interest.

Next, the backing with the upright fibers (pile) was attached to the nailers. (Fig. 9).

The infill material was then topdressed onto the plots using a traditional topdresser. (Fig. 10).

Infill materials varied. Some contained a mixture of sand and crumb rubber while some contained 100% crumb rubber (Fig. 11).

The crumb rubber was then worked into the pile using a power broom (Fig. 12). More infill was topdressed and power broomed. This process continued until the desired depth of infill was installed. The depth of the infill, for each product, is reported in Table 1.

Characterization of Infill Systems

The following are links to the specification sheets for the various products installed in the study.

Simulated Foot Traffic and Grooming

We began to impose simulated foot traffic during July of 2003. Traffic was applied using a Brinkman traffic simulator (Cockerham and Brinkman, 1989). The Brinkman Traffic Simulator weighs 410 kg and consists of a frame housing two 1.2-m long rollers (Fig. 12). Each roller has steel dowels or spriggs (12.7-mm diameter by 12.7-mm length) welded to the outside of the rollers, at an average of 150 dowels m^-2. These dowels are the approximate length and width of the cleats on the shoe of an American football lineman at the collegiate level. The Brinkman Traffic Simulator produces wear, compaction, and lateral shear. The drive thrust yielding lateral shear is produced by different sprocket sizes turning the rollers at unequal speeds. The Brinkman Traffic Simulator was pulled with a model 4200VXD Ventrac tractor (Venture Products, Inc. Orrville, OH) equipped with a dual turf tire package.

Plots were split with two levels of traffic. The traffic levels were no wear, and high wear (eight passes three times per week). According to Cockerham and Brinkman (1989), two passes of the Brinkman Traffic Simulator produces the equivalent number of cleat dents created between the hash marks at the 40-yard line during one National Football League game. Thus, 24 passes per week are equivalent to the cleat dents sustained from 12 games per week.

Traffic began on 7 Jul 2003 and 21 April 2004. Typically, traffic was applied regardless of weather conditions or water content of the infill. Numerous traffic applications occurred when the plots were very wet. Occasionally, due to heavy precipitation or schedule conflicts, traffic was not applied on the scheduled day. In these cases, traffic was applied on the following day.

In order to collect data, traffic was not applied for an approximately 3-week period at the end of July through early August in 2003 and 2004. Traffic resumed in mid August of each year and continued until 9 Oct 2003 and 8 Nov 2004. Plots were groomed on 9 Oct 2003 and again on 4 Aug 2004. Grooming consisted of loosening the granules using a 40" Lawn aerator (model # 45-0296 Agri-fab, Inc. Sullivan, IL) shown in Fig. 13.

Two passes with the lawn aerator were applied on each half of each plot with the second pass being 90° to the first. Following loosening of the granules, the pile above the infill material was broomed using a hand held power broom (Fig. 14) to try to return the pile to an upright position. Data collection again occurred during the week after grooming was complete.

Surface Hardness (Gmax) Method

Surface hardness was measured using a CIST equipped with a 2.25 kg (5 lb) missile and a drop height of 455 mm (American Society for Testing and Materials, 2000b) and the F355 method equipped with a 9.1 kg (20 lb) missile and a drop height of 610 mm (American Society for Testing and Materials, 2000a) (Fig 15). Impact attenuation, as measured by an accelerometer mounted on the missiles, was used to indicate surface hardness and is reported as Gmax, which is the ratio of maximum negative acceleration on impact in units of gravities to the acceleration due to gravity. The average of six CIST and three F355 measurements taken in different locations on each subplot was used to represent the surface hardness of that subplot. A single F355 measurement consists of dropping the missile three times in the same location with a three minute interval between each drop. The value reported as Gmax is the average of the second and third drop in the same location. When using the CIST we report the Gmax value we obtained with the first drop on the surface. Measurements were taken when the surface was free of moisture from dew or precipitation.

The experimental design was a completely random split-plot statistical design with three replications. The split was wear and no wear. The means of the six CIST and three F355 measurements were analyzed using analysis of variance and Fisher's least significant difference test at the 0.05 level. A LSD was not calculated when the F ratio was not significant at the 0.05 level.

Results and Discussion

For all results in this section it should be noted that this data is from the first two years of a long term study and represent only that time frame. These results will be updated as more data is collected during subsequent years.

F355

The Gmax, Severity Index, and Head Injury Criteria (HIC) for data collected during 2003 and 2004 are shown in Table 1 and 1a. We found that Gmax had a high correlation with the severity index (0.97) and head injury criteria (0.96). For this reason, we are currently suggesting that Gmax should be the main focus when comparing surface hardness values.

Table 1. Colony forming units (CFU) detected on R2A media per gram of crumb rubber.
Treatment	28-31 Jul 2003					8-12 Sep 2003
Treatment	Gmax¹	HIC²	SI³	Sub temp (°F)⁴	Infill depth (cm)	Gmax	HIC	SI	Sub temp (°F)	Infill depth (cm)
No Wear
Astroplay	75.0	173.5	201.1	78.9	4.2	79.7	183.8	231.3	73.0	4.0
Astroturf	113.3	244.7	293.1	82.2	0.7	102.1	244.0	285.9	78.2	NA
Experimental	81.1	182.2	211.7	76.5	3.6	83.1	195.9	227.9	75.4	3.5
Fieldturf	93.1	203.4	237.2	83.5	4.3	94.4	223.1	259.6	74.8	4.3
Geoturf	101.6	240.2	282.5	96.6	2.8	101.1	234.7	273.7	70.0	3.3
Nexturf	62.1	130.5	152.5	74.7	2.3	70.2	158.2	184.5	80.9	2.2
Omnigrass 41	83.3	198.2	229.7	83.4	4.0	87.7	208.6	241.9	69.2	3.9
Omnigrass 51	72.5	170.2	196.5	78.1	4.9	95.0	234.9	272.6	71.1	4.9
Sofsport	88.8	204.6	238.7	88.4	3.2	105.0	258.1	305.6	72.7	3.3
Sprinturf	101.9	235.3	276.0	79.2	2.6	102.8	236.7	278.7	73.6	2.8
Wear⁵
Astroplay	75.7	174.0	202.2	79.3	4.2	82.1	196.5	227.5	72.0	4.0
Astroturf	109.6	227.1	274.1	81.9	0.7	108.3	258.9	305.0	79.0	NA
Experimental	86.9	207.2	240.3	76.0	3.5	81.1	190.1	221.2	75.4	3.2
Fieldturf	95.3	214.2	250.3	79.2	4.2	95.1	225.5	261.9	75.8	4.2
Geoturf	95.4	217.9	254.5	88.7	3.1	100.6	239.7	279.3	71.3	3.1
Nexturf	64.8	139.4	164.1	75.0	2.2	68.7	152.0	177.6	87.3	1.8
Omnigrass 41	89.0	221.5	256.7	82.7	3.8	93.2	228.9	264.9	69.2	3.7
Omnigrass 51	78.3	193.0	222.8	82.1	4.8	90.9	219.9	255.3	71.7	4.6
Sofsport	88.9	209.8	244.2	86.8	3.1	103.8	252.8	299.7	72.6	3.1
Sprinturf	106.6	253.6	296.7	78.1	2.5	99.2	232.0	273.1	73.2	2.7
LSD (p=0.05)	6.1	24.1	28.0	4.5	0.3	8.0	29.2	33.8	2.5	0.2

¹Surface hardness was measured according to ASTM standard F355.
²HIC = Head Injury Index
³SI = Severity Index
⁴Subsurface temperature was measured 0.5 inch below the pile backing.
⁵July testing performed after wear simulating 36 games. September testing performed after wear simulating 88 games.

Table 1a. Surface harness (Gmax), Head Injury Criterion (HIC), Severity Index (SI), and pad temperature of ten synthetic turf products
Treatment	1-9 Jul 2004				10-25 Aug 2004
Treatment	Gmax¹	HIC²	SI³	Sub. temp (°F)	Gmax	HIC	SI	Sub. temp (°F)
No Wear
Astroplay	79.4	194.5	225.2	75.2	78.9	187.3	216.8	70.4
Astroturf	129.1	307.8	371.3	84.6	129.7	305.9	376.6	77.9
Experimental	80.4	176.6	204.6	79.2	87.6	201.7	234.3	76.5
Fieldturf	97.7	222.2	258.6	82.0	97.3	217.7	253.3	77.6
Geoturf	103.1	254.6	296.7	92.1	105.8	256.3	299.1	79.1
Nexturf	68.1	156.1	182.2	76.9	68.2	151.8	178.2	73.1
Omnigrass 41	90.4	231.9	268.6	83.0	95.5	250.4	289.7	79.0
Omnigrass 51	78.4	197.1	227.4	81.1	81.7	205.5	237.1	75.6
Sofsport	91.3	232.5	269.9	82.5	93.6	228.3	265.7	78.1
Sprinturf	112.0	275.2	323.3	82.3	113.6	261.1	306.8	74.1
Wear⁵
Astroplay	84.4	213.9	246.2	75.2	84.2	204.9	235.9	70.2
Astroturf	128.5	296.4	359.0	86.8	126.0	282.9	342.2	78.1
Experimental	94.9	217.9	254.8	79.8	96.0	230.9	268.6	76.5
Fieldturf	106.9	259.9	303.0	81.3	106.6	247.3	288.8	81.0
Geoturf	107.7	269.4	314.5	77.9	110.2	267.6	312.9	83.9
Nexturf	72.0	172.6	201.4	77.7	69.0	154.1	180.6	71.1
Omnigrass 41	101.3	275.5	319.2	83.3	102.0	273.9	316.8	78.0
Omnigrass 51	88.2	236.7	272.9	80.3	89.2	234.0	269.9	75.7
Sofsport	95.8	244.1	283.9	79.8	96.7	240.1	279.0	76.0
Sprinturf	126.3	316.2	373.3	83.7	126.2	289.8	341.4	75.1
LSD (p=0.05)	10.2	38.8	45.6	-	9.7	35.5	42.3	-

¹Surface hardness was measured according to ASTM standard F355.
²HIC = Head Injury Index
³SI = Severity Index
⁴Subsurface temperature was measured 0.5 inch below the pile backing.
⁵F355 testing performed after wear simulating 96 games. September testing performed after wear simulating 88 games.

The question remains: how hard is too hard? Grooming of plots occurred on 4 and 5 Aug 2004.

The need for a systematic means of evaluating the impact attenuation of an installed North American football playing system has been amply demonstrated by the current difficulty in establishing the shock absorbing properties of new and aging systems. The aim of this specification is to provide a uniform means and relatively transportable method of establishing this characteristic in the field based on historical data. According to historical data, the value of 200 G is considered to be a maximum threshold to provide an acceptable level of protection to users.

The test method used in this specification (Procedure A of Test Method F 355), has been documented, through "unofficial" use for testing impact in fields for over 20 years. The development of this 2 ft fall height method can be traced back to the Ford and General Motors crash dummy tests of the 1960's, medical research papers from the 1960's and 1970's, and a Northwestern University study in which an accelerometer was fixed to the helmet of a middle linebacker to measure the impact received during actual play. This study found the impact to be 40 ft/lb that translates to the 20 lb at a height of 2 ft used in Procedure A of Test Method F 355. The maximum impact level of 200 average Gmax, as accepted by the U.S. Consumer Product Safety Commission, was adopted for use here.

All of the surfaces measured were well below the maximum level of 200 Gmax even after the equivalent of 296 games of simulated traffic over two years. While open to debate, I suggest the upper limit should be set to 175 Gmax using the F355 method A. After two years of simulated wear, all synthetic surfaces in this study measured well below the suggested upper limit for surface hardness.

Clegg Impact Soil Tester (CIST)

The CIST is the standard method to measure the surface hardness of natural turfgrass playing surfaces (American Society for Testing and Materials, 2000b). The device is similar to the F355 method. Both systems have a weighted missile that is dropped through a guide tube and impacts the playing surface. Each missile contains an accelerometer that measures how quickly the missile stops upon impact. This impact attenuation is representative of surface hardness. The two devices use different weights. The F355 method uses a 20 lb weight and the CIST uses a 5 lb weight but has a smaller impact surface area. The impact energy of both devices is very similar; however, the CIST results in a lower Gmax reading compared to the F355. The F355 method also has a velocimeter that measures the velocity of the missile just prior to impact. This gives the F355 method an added measure of accuracy since the velocity of the missile is actually measured during each drop. When using the CIST, the velocity of the missile is assumed. The velocity of the CIST missile has been measured, but for any individual drop, the user must assume that the missile is traveling at the calculated velocity and nothing has interfered with that velocity.

In a previous study, McNitt and Landschoot (2004) reported that under the conditions of their study the relationship between the Gmax values generated by the first drop of the F355 method can be compared to the values generated by the CIST using the regression equation (F355 x 0.66) - 9.3 = CIST. The regression coefficient for this equation was 0.95. Although this study was limited to the Sofsport infill system, the high regression coefficient would indicate that the CIST would be a suitable device to measure the surface hardness of Sofsport installations. After two years of data on varying infill systems at varying levels of wear we have generated the following regression equations:

For the first drop of both devices:

(F355 x 0.76) - 27.5 = CIST with an R squared value of 0.87.

For the first drop of the CIST and the average of the second and third drop in the same location using the F355:

(F355 x 0.81) - 27.1 = CIST with an R squared value of 0.81.

Using the above regression equation a Gmax of 200 measured with the F355 would be equivalent to a Gmax of 135 measured with the CIST and a 2.25 kg missile. None of the treatments in this study exceeded the 200 Gmax limit measured with the F355 or the 135 Gmax measured with the CIST (Table 2).

Table 2. Number of colonies per swab detected on R2A media from various sources in public spaces and an athletic training facility.
Treatment	Gmax²
Treatment	4 Aug	27 Aug	20 Nov
No Wear
Astroplay	51.6	52.1	37.2
Astroturf	97.0	99.3	70.9
Experimental	61.6	64.8	41.5
Fieldturf	66.7	65.5	48.1
Geoturf	82.0	84.0	59.6
Nexturf	48.6	51.2	51.4
Omnigrass 41	61.3	62.6	42.9
Omnigrass 51	45.1	48.4	29.7
Sofsport	68.8	69.6	54.1
Sprinturf	86.3	90.2	60.4
Wear³
Astroplay	53.9	58.1	44.0
Astroturf	113.5	118.6	78.5
Experimental	65.3	70.8	47.9
Fieldturf	68.5	78.4	57.4
Geoturf	79.7	83.7	65.3
Nexturf	52.9	53.7	52.3
Omnigrass 41	65.8	70.6	50.4
Omnigrass 51	50.3	53.4	38.8
Sofsport	74.2	78.5	56.4
Sprinturf	93.7	101.2	65.2
LSD (p=0.05)	10.1	10.2	3.5

¹Grooming of wear and no wear plots occurred on 9-10 Oct 2003.
²Surface hardness was measured using a Clegg Impact Tester equipped with a 2.25 kg hammer.
³4 Aug testing performed after wear simulating 44 games. 27 Aug testing performed after wear simulating 84 games. 20 Nov testing performed after wear simulating 92 games and immediately after grooming.

We connected the CIST to a laptop computer and generated both the HIC and SI. The HIC and SI generated with the CIST were highly correlated to the Gmax value suggesting that Gmax is a sufficient measure of surface hardness (Table 3, 4 and 5).

Table 3. Surfaces that tested positive (+) for *S. aureus* colonies per swab detected.
Treatment	Severity Index²		Head Injury Criterion²
Treatment	4 Aug	27 Aug	4 Aug	27 Aug
No Wear
Astroplay	93.7	97.6	80.2	82.1
Astroturf	254.6	261.6	217.9	224.0
Experimental	130.6	137.5	112.5	118.4
Fieldturf	147.9	140.8	128.3	121.9
Geoturf	196.4	204.0	169.1	175.8
Nexturf	102.3	105.1	86.5	91.5
Omnigrass 41	131.9	135.1	113.5	116.3
Omnigrass 51	78.9	86.8	66.3	74.1
Sofsport	159.2	161.9	137.5	140.2
Sprinturf	207.3	220.3	177.7	189.4
Wear³
Astroplay	104.6	122.3	90.3	105.8
Astroturf	314.1	327.1	265.8	275.4
Experimental	140.9	162.6	121.0	139.8
Fieldturf	152.6	190.0	132.3	164.6
Geoturf	189.9	207.5	163.5	178.8
Nexturf	111.1	114.2	96.5	100.3
Omnigrass 41	150.9	166.9	130.2	143.8
Omnigrass 51	101.7	111.3	88.3	96.6
Sofsport	180.9	195.4	156.2	168.4
Sprinturf	231.4	256.2	197.4	218.3
LSD (p=0.05)	21.3	37.4	18.4	31.4

Table 4. Severity Index (SI) of infill systems on 2004 determined with the Clegg Impact Tester prior to and after grooming¹.
Treatment	Severity Index (SI)²
Treatment	25 May	20 Jul	6 Aug	3 Sep	7 Sep	13 Sep	16 Sep	29 Sep	5 Oct	14 Oct	21 Oct	28 Oct
No Wear
Astroplay	39.0	47.7	52.2	57.9	62.3	72.9	58.2	55.3	57.9	54.2	55.3	58.8
Astroturf	137.6	135.3	139.8	156.4	138.0	146.5	141.7	138.4	148.2	144.4	148.0	145.5
Experimental	58.6	59.1	74.1	83.0	91.5	77.7	77.1	64.3	79.2	76.8	68.7	75.4
Fieldturf	71.9	71.9	84.5	90.0	105.8	94.6	91.1	81.6	97.0	76.9	89.2	101.5
Geoturf	94.1	95.2	106.3	103.7	108.9	108.6	105.8	109.0	106.5	111.0	110.8	113.3
Nexturf	45.7	54.2	53.0	56.8	53.5	58.2	61.2	58.0	58.5	63.6	72.2	58.7
Omnigrass 41	62.0	62.0	64.6	79.3	85.1	82.5	70.6	66.3	75.5	71.5	65.3	72.3
Omnigrass 51	31.4	40.2	41.9	49.7	56.2	58.9	46.4	40.8	50.0	42.8	40.3	42.2
Sofsport	84.3	81.0	90.6	105.0	108.3	109.3	93.1	94.1	98.6	90.2	95.2	96.3
Sprinturf	80.9	91.6	11.5	125.3	124.0	112.8	112.8	100.5	116.7	111.5	108.4	116.2
Wear³
Astroplay	62.3	65.6	78.7	74.4	75.9	78.1	75.5	70.6	76.3	74.2	75.1	80.6
Astroturf	157.2	148.6	161.0	175.1	150.9	164.2	150.0	147.6	161.2	146.9	157.3	156.3
Experimental	80.7	75.9	84.1	88.5	98.1	78.4	89.2	72.9	90.2	89.6	86.2	95.5
Fieldturf	94.2	95.1	101.2	100.0	104.0	100.0	103.3	103.1	108.1	112.6	107.8	114.9
Geoturf	111.4	109.9	113.9	112.9	118.0	110.1	117.6	120.6	120.8	121.4	122.8	118.2
Nexturf	55.8	58.6	61.7	94.1	64.1	64.8	63.4	67.8	70.7	72.6	79.8	69.9
Omnigrass 41	83.3	77.4	82.6	100.4	96.5	97.9	83.1	80.2	90.0	86.7	88.5	90.6
Omnigrass 51	55.3	57.1	59.1	68.4	72.4	71.1	62.9	60.8	66.5	66.3	66.6	68.3
Sofsport	98.1	92.1	99.4	109.2	112.6	115.3	101.4	95.4	105.6	100.4	102.9	106.5
Sprinturf	120.2	102.8	124.3	142.8	140.2	122.7	126.9	106.6	125.5	123.6	117.8	135.4
LSD (p=0.05)	13.8	13.3	18.3	19.4	16.8	12.8	13.3	16.5	13.8	13.3	17.0	15.7

¹Grooming of wear and no wear plots occurred on 4-5 Aug 2004.
²Surface hardness was measured using a Clegg Impact Tester equipped with a 2.25 kg hammer.
³25 May testing performed after wear simulating 32 games. 20 Jul testing performed after wear simulating 96 games. 6 Aug testing performed after grooming. 7 Sep testing performed after wear simulating 8 games after grooming. 16 Sep testing performed after wear simulating 20 games after grooming. 29 Sep testing performed after wear simulating 36 games after grooming. 5 Oct testing performed after wear simulating 48 games after grooming. 14 Oct testing performed after wear simulating 64 games after grooming. 21 Oct testing performed after wear simulating 80 games after grooming. 28 Oct testing performed after wear simulating 92 games after grooming.

Table 5. Head Injury Criterion (HIC) of infill systems determined in 2004 with the Clegg Impact Tester prior to and after grooming¹.
Treatment	Head Injury Criterion (HIC)²
Treatment	25 May	20 Jul	6 Aug	3 Sep	7 Sep	13 Sep	16 Sep	29 Sep	5 Oct	14 Oct	21 Oct	28 Oct
No Wear
Astroplay	33.5	40.6	45.0	50.0	52.4	58.6	48.9	47.1	46.8	47.1	48.1	51.2
Astroturf	116.7	116.0	118.5	131.1	116.6	124.4	121.5	118.6	121.8	124.7	130.0	125.1
Experimental	50.9	51.2	63.4	71.0	77.5	65.7	66.0	61.9	64.5	66.7	59.6	65.0
Fieldturf	62.8	62.7	73.6	78.4	91.6	80.4	78.6	70.9	81.5	86.9	77.8	88.5
Geoturf	80.9	81.6	89.9	87.2	92.0	87.3	88.0	91.7	88.8	92.3	95.0	97.4
Nexturf	40.0	45.2	42.4	45.6	44.2	47.7	47.9	49.8	49.7	56.6	63.5	51.7
Omnigrass 41	53.9	53.8	54.6	67.3	73.1	68.1	57.6	55.9	63.7	61.3	56.6	62.6
Omnigrass 51	26.8	31.8	34.1	40.3	47.9	46.5	35.5	33.5	41.3	35.0	35.2	36.9
Sofsport	72.2	70.3	78.5	90.4	91.8	92.3	78.7	80.1	83.7	77.7	82.6	83.5
Sprinturf	69.9	88.1	95.7	106.8	104.3	94.5	93.1	84.4	96.5	95.9	92.9	99.8
Wear³
Astroplay	54.2	57.1	68.6	63.3	64.3	64.5	64.5	58.8	62.0	64.5	65.3	70.1
Astroturf	132.5	126.5	135.9	146.9	126.6	135.1	127.8	125.9	132.4	125.2	137.6	133.5
Experimental	69.9	46.5	72.3	75.9	82.5	66.5	75.6	61.9	74.4	77.6	74.7	82.7
Fieldturf	81.7	82.7	87.9	86.6	90.0	84.1	88.0	87.9	90.0	96.8	93.4	99.5
Geoturf	95.8	94.3	97.9	95.2	101.3	90.6	98.9	101.3	100.3	101.6	104.7	101.2
Nexturf	48.7	51.8	53.2	55.3	53.8	54.2	54.1	57.4	59.5	64.6	71.0	61.1
Omnigrass 41	72.2	67.2	71.2	85.2	83.4	83.4	69.2	67.0	74.3	72.7	75.5	78.5
Omnigrass 51	48.4	49.8	51.6	58.4	61.6	59.9	51.2	33.5	55.7	56.1	57.4	59.6
Sofsport	84.8	79.6	85.6	94.2	94.7	95.4	84.7	80.1	87.2	84.7	88.4	92.0
Sprinturf	102.9	88.1	106.7	120.7	117.0	103.3	108.0	89.3	103.4	105.8	101.0	115.4
LSD (p=0.05)	11.8	16.8	15.4	16.8	13.9	10.7	11.6	14.2	12.2	10.8	14.3	13.3

The lower half of the first two columns of data in Tables 2 and 3 is after simulated traffic equaling 44 and 84 games, respectively. The top half of the table is data collected from the half of the plot not receiving traffic. The third column (20 Nov) is data collected immediately after grooming. It is apparent from this data that grooming significantly reduced the surface hardness of all treatments in 2003. This was not the case in 2004 as grooming seemed to have little consistent affect on surface hardness (Table 6). This may be due to the aging of the systems or due to the unseasonably cold wet summer we experienced in 2004. Weekly Gmax measurements were collected using the CIST. The results are shown in Table 6. This was done in an attempt to monitor the duration of the effect of grooming on Gmax values. Our results indicate that the Gmax values of these surfaces remained relatively consistent from fall of 2003 through October 2004. It is unlikely that the effects of grooming last this long. In fact, the F355 data indicates that the surfaces trended higher in Gmax values in 2004 compared to 2003.

Table 6. Surface hardness (Gmax) of infill systems determined in 2004 with the Clegg Impact Tester prior to and after grooming¹ but were not consistent.
Treatment	Gmax²
Treatment	25 May	20 Jul	6 Aug	3 Sep	7 Sep	13 Sep	16 Sep	29 Sep	5 Oct	14 Oct	21 Oct	28 Oct
No Wear
Astroplay	33.8	36.5	38.3	40.0	41.5	44.2	40.1	39.2	43.9	39.3	39.8	41.2
Astroturf	73.6	72.8	74.2	79.6	74.2	77.3	75.0	73.0	76.4	74.8	79.3	75.9
Experimental	41.2	42.3	47.6	49.3	52.8	47.9	47.7	48.0	55.2	48.8	46.6	48.1
Fieldturf	47.7	48.0	52.6	53.8	60.1	55.7	54.6	51.9	65.2	58.3	55.1	59.4
Geoturf	58.2	58.3	62.0	60.9	63.3	60.7	61.4	62.5	61.8	62.8	63.4	64.6
Nexturf	35.3	36.9	35.6	36.9	36.7	38.0	38.4	39.2	42.4	42.9	46.4	40.4
Omnigrass 41	42.5	42.4	42.8	47.7	50.1	48.4	44.4	44.1	47.0	46.6	44.3	47.1
Omnigrass 51	29.9	31.3	32.1	34.6	38.5	37.4	34.1	32.3	36.6	32.7	33.4	33.6
Sofsport	51.2	50.3	53.6	58.2	58.8	59.7	53.7	54.5	56.9	53.7	55.8	56.5
Sprinturf	52.0	58.1	65.4	67.6	66.2	62.7	64.5	61.5	65.7	65.7	65.0	66.6
Wear³
Astroplay	42.4	43.8	48.2	45.4	46.0	46.7	46.3	44.4	54.9	46.6	47.1	48.8
Astroturf	82.4	78.6	82.4	87.7	74.2	82.5	78.6	76.9	82.0	75.4	79.3	80.5
Experimental	49.8	49.2	51.7	52.0	54.9	47.9	52.2	48.0	58.8	53.8	53.3	55.6
Fieldturf	56.4	57.1	58.9	57.9	59.8	57.2	59.3	59.9	64.1	63.4	62.2	64.4
Geoturf	64.2	63.7	64.5	64.3	66.4	62.0	66.0	66.8	66.2	67.0	68.6	66.7
Nexturf	38.5	39.2	39.6	40.2	40.0	40.2	40.2	41.5	55.7	45.2	48.1	43.9
Omnigrass 41	50.5	48.8	50.5	55.1	55.1	55.1	49.6	49.2	51.5	51.6	44.3	53.8
Omnigrass 51	38.5	39.1	39.8	42.6	43.9	43.5	39.5	38.6	41.8	42.2	33.4	43.7
Sofsport	56.7	54.6	56.7	60.3	60.7	61.7	56.8	55.2	59.1	57.2	58.7	59.9
Sprinturf	68.3	64.4	71.3	74.1	72.1	67.8	71.6	65.5	69.8	71.2	69.8	74.3
LSD (p=0.05)	5.5	5.8	6.9	7.0	6.4	5.1	5.8	7.2	8.6	5.9	6.7	6.2

These data may be a result of the cool wet conditions that prevailed in 2004. Another possibility is that as these systems age and become less resilient, the heavier missile of the F355 method, which takes the average of the second and third successive drop in the same location, is experiencing a higher Gmax due to the heavier load at impact. After maximum impact attenuation of the infill and fiber system is reached, the accelerometer in these devices will begin to be affected by the impact attenuation of the surface below the backing. Henderson (1986) found that a rock can be sensed by the F355 method when it is four inches below the surface of a natural turfgrass playing field. The reason for this difference will likely become clearer as successive years of data are collected. Currently, we are suggesting the CIST as a tool for grounds managers to monitor their field throughout the season and recommending the F355 device be employed at least annually.

The following data is provided to give some reference points for the Gmax values generated using the CIST.

Table 7. Impact values for high school fields vs. impact values for other surfaces
Surface	Hammer 2.25 kg Gmax
High school fields	33-167
Frozen practice field	303
Tiled, concrete basement floor	1,280
Carpet and pad on tiled concrete floor	190
Carpet and pad on hardwood floor	134

Gmax = maximum deceleration

During 2004, we applied simulated foot traffic to a very well established Kentucky bluegrass (Poa pratensis, L.) turfgrass (33% Liberator, 33% Washington and 33% Touchdown) at the same rate and intensity as we applied it to the synthetic turf systems.

A significant amount of turfgrass cover was lost. On the 9 Jul 205 rating date, the average turf cover was 65% (Fig. 16). In order to coincide with grooming of the synthetic turf, the natural turf area was aerated in August using 3/4 inch tines on 3 x 2 in. center and rested for about one month. The plots recovered to about 90% turf cover (Fig. 17). Wear continued and by 8 Nov 2004 the plot area averaged 40 - 45% turf cover (Fig. 18). This turf area was well maintained. During the 2004 growing season nitrogen fertilization on this plot area was 3.5 lbs N per thousand feet squared and irrigation was applied to prevent drought stress. The soil was a Hagerstown silt loam. Prior to the beginning of simulated wear, the thatch thickness of the plot area averaged 3/4 in. The data listed in Table 8 indicate that the surface hardness of the natural turf area was the same or higher than most of the infill systems' Gmax values listed in Table 2. On a native soil turfgrass surface, Gmax is greatly affected by soil moisture. Soil moisture values for some rating dates are listed and were high for 2004 as it was a very wet summer and fall. During dry conditions, we would expect these values to increase.

Table 8. Surface hardness (Gmax) and soil moisture content in 2004 of a natural turfgrass test area

Gmax
	Clegg¹										F333³
	25 May	20 Jul	7 Sep	13 Sep	16 Sep	29 Sep	5 Oct	14 Oct	21 Oct	28 Oct	2 Jul
Wear²	50.4	70.1	74.8	68.4	84.1	70.3	83.6	79.3	56.3	61.0	88.3
No Wear	50.4	55.5	66.9	66.2	67.4	59.3	67.9	69.7	53.7	54.9	83.3

¹Surface hardness was measured using a Clegg Impact Tester equipped with a 2.25 kg hammer.25 May testing performed after wear simulating 32 games. 20 Jul testing performed after wear simulating 96 games. Aerification of wear and no wear areas occurred on 6 Aug 2004. The area was aerified with 0.75" hollow tines. 7 Sep testing performed after wear simulating 8 games after aerification. 13 Sep testing performed after wear simulating 12 games after aerification. 16 Sep testing performed after wear simulating 20 games after aerification. 29 Sep testing performed after wear simulating 36 games after aerification. 5 Oct testing performed after wear simulating 48 games after aerification. 14 Oct testing performed after wear simulating 64 games after aerification. 21 Oct testing performed after wear simulating 80 games after aerification. 28 Oct testing performed after wear simulating 92 games after aerification.
²Plots receiving wear treatments were exposed to wear as eight passes three times per week with the Brinkman Traffic simulator beginning on 21 Apr and ending on 8 Nov.
³Surface hardness was measured according to ASTM standard F355. 2 Jul testing performed after wear simulating 96 games.

% Moisure⁴
	2 Jul	20 Jul	16 Sep	29 Sep	28 Oct
Wear	29.9	36.0	23.8	35.1	36.1
No Wear	30.7	34.9	30.2	33.7	34.2

⁴Percent soil moisture (M³M^-3) was determined using a Dynamax Theta Meter Type HH1 at the same time gmax reading were collected.

Infill Media and Underlying Pad

The following is a short description of a prior study conducted by McNitt and Landschoot (2004). For a copy of the complete study click the reference below.

The objective of this study was to evaluate the surface hardness of varying configurations of an infilled synthetic turf system called SofSport^TM under wet and dry conditions. Specifically, we wanted to 1) determine the effect of underlying pad thickness and type, infill media depth, sand sizes, and sand to crumb rubber ratio, on surface hardness as measured by the F355 method and the CIST and 2) compare the F355 method with the CIST to determine if one method is preferred when testing synthetic infill systems. Surface hardness differences between pad thickness and types were small but all pad treatments had lower surface hardness values compared to the no-pad treatments. Infill media depth did not affect surface hardness under dry conditions. Under wet conditions, the 38 mm infill media depth resulted in lower surface hardness than the 25 mm depth. The mixing of sand and crumb rubber infill media resulted in lower surface hardness values than sand or crumb rubber alone. When mixed with crumb rubber, finer sands measured higher in surface hardness than coarser sands. Under the conditions of this study the relationship between the Gmax values generated by the F355 method can be compared to the values generated by the Clegg Impact Soil Tester using the regression equation F355 x 0.66 - 9.3 = Clegg Impact Soil Tester. The regression coefficient for this equation was 0.95 and indicates that the Clegg Impact Soil Tester would be a suitable device to measure the surface hardness of SofSport installations.

McNitt, A.S., P.J. Landschoot, and D. Petrunak. 2004. Evaluation of playing surface quality of an infilled synthetic turf system. Acta Horticulture 661:559-565.

Traction Data Collection

For all results in this section it should be noted that this preliminary data is from the first two years of a long term study. These results will be updated as more data is collected.

Translational, rotational, static, and dynamic traction have been defined by Shorten and Himmelsbach (2002).

Translational traction refers to the traction that resists the shoe's sliding across the surface. For the athlete, high translational traction equates to the shoe gripping the surface and low translational traction means the shoe tends to slip.

Rotational traction refers to the traction that resists rotation of the shoe during pivoting movements. For the athlete, high rotational traction equates to a greater tendency for foot fixation during changes of direction and low rotational traction means the shoe tends to release from the surface more easily.

Static and dynamic traction represent slightly different aspects of the shoe-surface interaction. Static traction is the resistance to sliding or pivoting when there is no movement between the shoe and the surface. Static traction forces tend to resist the initiation of sliding or pivoting. Dynamic traction is the resistance that occurs during a sliding or pivoting motion. Dynamic traction forces tend to resist or decelerate pivoting motions.

In this study traction was measured using Pennfoot (McNitt et al., 1997). Pennfoot conforms to the proposed traction standard ASTM WK486 (American Society for Testing and Materials, 2000c) standard traction measurements and is shown in Fig. 19.

Description and Operation of Pennfoot

Pennfoot consists of a frame which supports a steel leg with a cast aluminum foot pinned on the lower end of the leg. We cast the simulated foot from a size 10 foot mold and the foot can be fitted with different athletic footwear (Fig. 20). Two holes located on top of the foot are used for connection with the leg. The first hole located toward the toe allows us to raise the heel off the ground and distribute the weight on the ball of the foot. We took all traction measurements in this study with the forefoot in contact with the surface and the heel of the foot raised off the ground.

Pennfoot allows us to measure rotational or translational traction. For translational traction the linear force is created by a single pulling piston that is connected to the heel of the foot (Fig. 21). The pressure applied to the piston is created with a motorized hydraulic pump and monitored with a pressure transducer connected to a computer. The pressure readings are converted to Newtons (N) by multiplying the effective area of the pulling piston by the amount of pressure required to maintain movement of the shoe. The rate of linear travel is approximately 0.5 m s ^-1. Linear traction is thus measured as the amount of horizontal force (N) required to maintain translational movement at the given rate. It is customary to report a traction coefficient as the horizontal force divided by the vertical force. In the primary experiment all traction measurements were taken using a vertical force, or loading weight of 237 lbs. and a Nike Air Zoom high top shoe (Fig 22. original shoe). During 2004, we also tested a standard 7 post shoe (Fig 23. 7 shoe). In 2004, we tested select surfaces in both wet and dry conditions and we measured traction on all surfaces at a lower loading weight (119 lbs.).

When using Pennfoot to measure rotational traction, the rotating horizontal force is created by two pistons which are horizontally mounted on angle iron 38.1 cm above the ground as measured with the machine in position to take a measurement (Fig. 24). We connected a strike plate to the simulated leg for the pistons to push against. A lower collar around the simulated leg prevented it from tilting while the rotational force was applied. For a thorough description of design rationale and construction details of Pennfoot see McNitt et al. (1997).

The experimental design for the primary experiment was a completely random split-plot statistical design with three replications. The split was wear and no wear. Three Pennfoot measurements were taken for each subplot in this study. The means of the three linear and three rotational traction measurements were analyzed using analysis of variance and Fisher's least significant difference test at the 0.05 level. A LSD was not calculated when the F ratio was not significant at the 0.05 level.

Results and Discussion

The following is quoted directly from a study conducted by Shorten and Himmelsbach (2002).

Because of the link between foot fixation and knee injuries, resistance to rotation (rotational traction) between the shoe and the ground should be as low as possible providing adequate translational traction is maintained.

Other studies have postulated a link between higher resistance to rotation and injury rates. While many reports have shown that injury rates are 30 to 50% higher on (traditional) artificial turf (Cameron and Davis, 1973; Henschen et al., 1989; Skovron et al., 1990; Powell and Shootman, 1992; Zemper, 1989) others have failed to find significant differences in injury rates (Clarke and Miller, 1977; Culpepper and Morrison, 1987) One concern with all of these studies is that only surface effects were considered while it is the combination of both the shoe and the surface that is implicated in traction related injuries.

Torg et al. (1978) found that high school football players wearing shoes with shorter cleats had a lower injury rate than those using longer cleats, a difference attributable to differences in the shoes' rotational traction.

More recently, Lambson et al. (1999) studied the relationship between the rotational resistance of shoes and the incidence of anterior cruciate ligament tears among 3119 high school football players. Shoes with peripheral cleats were associated with a significantly higher injury rate, compared with other shoe types.

In summary, there is strong evidence that excessive resistance to rotation at the shoe-surface interface increases the risk of foot fixation and hence of lower extremity injuries. There is also ample evidence that this mechanism contributes to a higher rate of injury among football players playing on (traditional) artificial turf, although this issue remains controversial among parties with interests in artificial turf systems.

For these reasons, we chose to measure both rotational and translational (linear) traction.

Translational and rotational traction values for treatments are shown in Tables 9 and 10.

Table 9. Linear traction determined in 2003 by ASTM traction standard and 237 pounds of vertical force prior to and after grooming ¹.
Treatment	September 2003		October 2003
Treatment	Static²	Dynamic³	Static	Dynamic
No Wear
Astroplay	1.22	1.10	1.42	1.17
Astroturf	1.65	1.46	1.83	1.41
Experimental	1.32	1.05	1.50	1.14
Fieldturf	1.42	1.21	1.50	1.19
Geoturf	1.37	1.24	1.48	1.29
Nexturf	1.31	1.00	1.51	1.15
Omnigrass 41	1.30	1.12	1.38	1.13
Omnigrass 51	1.37	1.20	1.46	1.18
Sofsport	1.30	1.16	1.56	1.26
Sprinturf	1.23	1.07	1.44	1.13
Wear⁴
Astroplay	1.30	1.04	1.47	1.18
Astroturf	1.52	1.46	1.60	1.33
Experimental	1.41	1.17	1.43	1.15
Fieldturf	1.35	1.04	1.58	1.22
Geoturf	1.26	1.12	1.44	1.31
Nexturf	1.38	1.06	1.50	1.21
Omnigrass 41	1.45	1.23	1.55	1.27
Omnigrass 51	1.40	1.25	1.56	1.32
Sofsport	1.36	1.21	1.44	1.24
Sprinturf	1.25	1.15	1.38	1.13
LSD (p=0.05)	0.14	0.13	0.11	0.16

¹Grooming of wear and no wear plots occurred on 9-10 2003.
²Static traction.
³Dynamic traction.
⁴September testing performed after wear simulating 88 games. October testing performed after wear simulating 92 games.

Table 10. Rotational traction determined in 2003 by ASTM traction standard prior to and after grooming ¹.
Treatment	Rotational traction (Nm)²
Treatment	24-Sep	30-Oct
No Wear
Astroplay	66.7	66.8
Astroturf	70.9	69.0
Experimental	63.0	67.7
Fieldturf	66.0	63.0
Geoturf	69.3	68.1
Nexturf	67.7	67.0
Omnigrass 41	66.0	65.9
Omnigrass 51	68.0	67.3
Sofsport	64.7	67.9
Sprinturf	64.6	65.5
Wear³
Astroplay	68.9	67.1
Astroturf	69.1	68.8
Experimental	67.9	65.4
Fieldturf	68.0	66.5
Geoturf	69.6	70.4
Nexturf	70.3	67.1
Omnigrass 41	66.7	65.4
Omnigrass 51	67.6	67.2
Sofsport	68.7	67.9
Sprinturf	66.2	66.6
LSD (p=0.05)	6.6	2.9

¹Grooming of wear and no wear plots occurred on 9-10 Oct 2003.
²Rotational traction.
³24 Sep testing performed after wear simulating 76 games. 30 Oct testing performed after wear simulating 92 games.

During 2003, there were few meaningful traction differences between synthetic turf systems. Traditional Astroturf measured consistently higher in linear traction compared to the infill systems. This trend was not evident in the rotational traction results in 2003.

The 30 Oct 2003 data were collected shortly after grooming had taken place. Translational traction tended to increase after grooming whereas rotational traction tended to have no change or trend slightly lower. This data indicates that, immediately after grooming, an athlete will experience increased translational (linear) traction and either no change or a slight decrease in rotational traction, thus allowing football lineman more traction when pushing but affecting no change or a slight reduction in the rotational foot fixation that Shorten and Himmelsbach (2002) state has a direct affect on lower extremity injuries.

In 2004, there continued to be a trend of increased linear traction after grooming for the no wear treatments but the trend was less evident in the treatments receiving wear (Tables 11 and 12). It may be that as these systems age, grooming will have a diminished affect on linear traction.

Table 11. Linear and rotational traction determined in 2004 by ASTM traction standard and 237 pounds of vertical force prior to grooming¹.
Treatment	Static²		Dynamic³		Rotational⁴
Treatment	Dry	Wet⁵	Dry	Wet	Dry	Wet
No Wear
Astroplay	1.43	-	1.24	-	90.6	-
Astroturf	1.59	-	1.33	-	88.9	-
Experimental	1.49	-	1.18	-	98.0	-
Fieldturf	1.53	1.30	1.22	1.00	109.4	84.6
Geoturf	1.51	-	1.36	-	87.5	-
Nexturf	1.47	-	1.20	-	89.6	-
Omnigrass 41	1.47	1.21	1.25	1.03	90.5	79.3
Omnigrass 51	1.49	1.23	1.27	1.01	84.7	90.0
Sofsport	1.53	-	1.26	-	81.0	-
Sprinturf	1.43	1.10	1.14	0.98	91.9	78.1
LSD	0.11	0.04	0.08	0.02	16.2	0.1
Wear⁶
Astroplay	1.52	-	1.25	-	92.6	-
Astroturf	1.54	-	1.39	-	81.3	-
Experimental	1.51	-	1.27	-	82.7	-
Fieldturf	1.64	1.29	1.30	1.05	84.1	83.6
Geoturf	1.45	-	1.34	-	72.1	-
Nexturf	1.50	-	1.23	-	84.1	-
Omnigrass 41	1.64	1.29	1.30	1.05	89.2	80.8
Omnigrass 51	1.58	1.28	1.34	1.08	79.0	81.8
Sofsport	1.48	-	1.22	-	86.3	-
Sprinturf	1.48	1.18	1.21	0.99	87.8	77.4
LSD	0.11	0.04	0.08	0.02	16.2	0.1

¹Testing was performed on 20-21 Jul, 23 Jul, and 28 Jul after wear simulating 96 games. The shoe used for testing was a Nike Air Zoom high-top shoe with a molded sole.
²Static traction
³Dynamic traction
⁴Rotational traction
⁵Readings were taken when the surface was wet following 0.28" rain or 0.25" irrigation.
⁶Plots receiving wear were exposed to wear as eight passes three times per week with the Brinkman Traffic simulator beginning on 21 Apr and ending on 8 Nov 2004. Plots were groomed on 4-5 Aug 2004.

Table 12. Linear and rotational traction determined in 2004 by ASTM traction standard and 237 pounds of vertical force after grooming¹.
Treatment	Static²	Dynamic³	Rotational⁴
No Wear
Astroplay	1.47	1.28	88.6
Astroturf	1.70	1.58	84.6
Experimental	1.52	1.22	81.7
Fieldturf	1.57	1.28	76.3
Geoturf	1.52	1.37	80.2
Nexturf	1.51	1.30	78.1
Omnigrass 41	1.50	1.28	79.1
Omnigrass 51	1.53	1.31	74.1
Sofsport	1.55	1.27	82.3
Sprinturf	1.42	1.15	81.7
LSD	0.07	0.10	7.5
Wear⁵
Astroplay	1.53	1.32	76.4
Astroturf	1.58	1.34	91.8
Experimental	1.53	1.34	78.1
Fieldturf	1.51	1.30	81.7
Geoturf	1.45	1.31	79.6
Nexturf	1.51	1.29	74.8
Omnigrass 41	1.59	1.31	84.9
Omnigrass 51	1.58	1.38	78.6
Sofsport	1.49	1.33	82.1
Sprinturf	1.50	1.28	79.6
LSD	0.07	0.10	7.5

¹Testing was performed from 31 Aug to 2 Sep after wear simulating 96 games and grooming of the plots. Grooming occurred on 4-5 Aug 2004. The shoe used for testing was a Nike Air Zoom high-top shoe with a molded sole.
²Static traction
³Dynamic traction
⁴Rotational traction
⁵Plots receiving wear were exposed to wear as eight passes three times per week with the Brinkman Traffic simulator beginning on 21 Apr and ending on 8 Nov 2004. Plots were groomed on 4-5 Aug 2004.

During 2004, grooming resulted in a greater reduction in rotational traction compared to 2003 (Tables 11 and 12). This was true regardless of shoe type. The data in Tables 13 and 14 indicate that grooming resulted in a consistent increase in linear traction, measured using a nine post shoe, and a general but less consistent decrease in rotational traction.

Table 13. Linear and rotational traction determined in 2004 by ASTM traction standard and 237 pounds of vertical force prior to grooming¹ using a 7 post cleated shoe.
Treatment	Static²	Dynamic³	Rotational⁴
No Wear
Astroplay	1.41	1.13	79.4
Astroturf	1.25	1.18	79.6
Experimental	1.44	1.17	82.9
Fieldturf	1.52	1.36	70.4
Geoturf	1.42	1.12	77.6
Nexturf	1.17	0.86	79.7
Omnigrass 41	1.37	1.12	70.9
Omnigrass 51	1.30	1.07	80.3
Sofsport	1.57	1.28	84.1
Sprinturf	1.42	1.15	80.6
LSD	0.10	0.06	10.8
Wear⁵
Astroplay	1.47	1.14	78.6
Astroturf	1.20	1.09	101.2
Experimental	1.40	1.11	80.1
Fieldturf	1.64	1.33	77.9
Geoturf	1.41	1.09	82.5
Nexturf	1.08	0.84	80.6
Omnigrass 41	1.47	1.15	77.8
Omnigrass 51	1.48	1.16	75.8
Sofsport	1.54	1.17	84.0
Sprinturf	1.48	1.12	82.8
LSD	0.10	0.06	10.8

¹Testing was performed from 22 Jul and 3 Aug after wear simulating 96 games. The shoe used for testing was a Reebok MidVisious 7 POST shoe with screw-in cleats.
²Static traction
³Dynamic traction
⁴Rotational traction
⁵Plots receiving wear were exposed to wear as eight passes three times per week with the Brinkman Traffic simulator beginning on 21 Apr and ending on 8 Nov 2004. Plots were groomed on 4-5 Aug 2004.

Table 14. Linear and rotational traction of plots received wear determined in 2004 by ASTM traction standard and 237 pounds of vertical force after grooming¹ using a 7 post cleated shoe.
Treatment	Static²	Dynamic³	Rotational⁴
Astroplay	1.62	1.23	72.8
Astroturf	1.23	1.12	93.6
Experimental	1.59	1.21	74.2
Fieldturf	1.72	1.41	86.7
Geoturf	1.74	1.21	84.6
Nexturf	1.22	0.91	78.5
Omnigrass 41	1.67	1.28	75.6
Omnigrass 51	1.58	1.26	88.0
Sofsport	1.66	1.21	77.5
Sprinturf	1.61	1.21	81.8
LSD	0.10	0.18	10.3

¹Testing was performed on 27 Aug and 2 Sep 2004 after wear simulating 96 games and grooming of the plots. The shoe used for testing was a Reebok MidVisious 7-post shoe with screw-in cleats.
²Static traction
³Dynamic traction
⁴Rotational traction

When traction was measured on the various surfaces during wet conditions traction was generally reduced (Table 11). A lower loading weight resulted in higher traction coefficients for linear measurements. It is not customary to calculate rotational traction coefficients; however, the data in Table 15 was collected using a loading weight that was half that of the data in Table 11. When considered proportionally, the traction values reported in Table 15 follow the same trend as the linear traction values.

Table 15. Linear and rotational traction determined in 2004 by ASTM traction standard and 119 pounds of vertical force prior to grooming¹.
Treatment	Static²	Dynamic³	Rotational⁴
No Wear
Astroplay	1.61	1.44	79.0
Astroturf	2.43	1.88	89.0
Experimental	1.73	1.37	87.8
Fieldturf	1.78	1.37	80.3
Geoturf	1.71	1.51	76.6
Nexturf	1.50	1.38	87.0
Omnigrass 41	1.64	1.36	84.6
Omnigrass 51	1.69	1.36	76.4
Sofsport	1.70	1.45	82.5
Sprinturf	1.50	1.34	80.0
LSD	0.15	0.08	9.7
Wear⁵
Astroplay	1.78	1.51	82.2
Astroturf	2.35	1.80	79.2
Experimental	1.77	1.45	86.3
Fieldturf	1.88	1.48	78.6
Geoturf	1.73	1.53	83.7
Nexturf	1.63	1.40	76.7
Omnigrass 41	1.84	1.48	90.4
Omnigrass 51	1.84	1.48	76.3
Sofsport	1.82	1.51	75.0
Sprinturf	1.66	1.50	82.9
LSD	0.15	0.08	9.7

¹Testing was performed from 21-22 Jul and 2 Aug after wear simulating 96 games. The shoe used for testing was a Nike Air Zoom high-top shoe with a molded shoe.
²Static traction
³Dynamic traction
⁴Rotational traction
⁵Readings were taken when the surface was wet following 0.28" rain or 0.25" irrigation.
⁶Plots receiving wear were exposed to wear as eidht passes three times per week with the Brinkman Traffic simulator beginning on 21 Apr and ending on 8 Nov 2004. Plots were groomed on 4-5 Aug 2004.

Comparing the data from 2004 to the data collected in 2003, linear traction decreased with age while rotational traction increased. With only two years of data it is impossible to predict if this trend will continue.

Traction measurements were collected on the natural turfgrass areas during 2004 and are shown in Table 16. Comparing traction values using the same loading weight and shoe type, the data indicates similar or lower linear traction and similar or higher rotational traction of the natural turfgrass compared to synthetic surfaces. Very little data was collected on the natural turfgrass as turf and soil conditions fluctuated. The natural turfgrass data is from one rating date and one soil moisture condition.

Table 16. Translational (static and dynamic) and rotational traction ¹ of Kentucky bluegrass (*Poa pratentis*, L.) in 2004 using tow shoes and two loading weights.
7 Post shoe² 237lb leg apparatus³
	Static	Dynamic	Rotational (Nm)
Wear⁴	1.66	1.50	102.3
No Wear	1.68	1.63	95.7
Molded sole shoe⁵ 119lb leg apparatus⁶
	Static	Dynamic	Rotational (Nm)
Wear⁴	1.41	1.17	72.1
No Wear	1.51	1.14	105.4
Molded Sole shoe 237lb leg apparatus⁷
	Static	Dynamic	Rotational (Nm)
Wear⁴	1.25	1.01	97.3
No Wear	1.19	0.93	108.3

¹Traction was measured using Pennfoot, which conforms to the proposed traction standard ASTM WK486
²The shoe used is a Reebok MidViscious 7 post shoe with screw-in cleats.
³Static and dynamic traction data were collected on 22 Jul 04. Rotational traction data were collected on 3 Aug 04.
⁴The area receiving wear was exposed to wear as eight passes three times per week with the Brinkman Traffic simulator beginning on 21 Apr 04 and ending on 8 Nov 04. Data were collected from the area receiving wear after traffic simulating 96 games.
⁵The molded sole shoe used is a Nike Air Zoom turf shoe.
⁶Static and dynamic traction data were collected on 22 Jul 04. Rotational traction data were collected on 2 Aug 04.
⁷Static and dynamic traction data were collected on 22 Jul 04. Rotational traction data were collected on 28 Jul 04.

Abrasion

Abrasiveness was measured using ASTM F1015 method (ASTM 2000e). Friable foam blocks were attached to a weighted platform that was pulled over the playing surface in four directions (Fig 25 and 26). The weight of foam abraded away determines the relative abrasiveness of the surface. The friable foam blocks used as the test material were rigid closed-cell isocyanurate. An abrasiveness index is calculated by taking the weight loss for each set of four blocks in grams and dividing by 0.0606 as per ASTM F1015.

Abrasion data is shown in Table 17. All infilled treatments were less abrasive than Astroturf. For treatments receiving wear, the abrasion index was lower in 2004 (Table 18) compared to 2003. This trend was not evident in the no-wear treatments. Grooming tended to lower the abrasiveness of the treatments. We continue to try to modify the abrasion testing method so we can produce data on natural turf.

Table 17. Abrasion index of ten synthetic turf products in 2003 prior to and after grooming.¹
Treatment	Abrasion Index²
Treatment	7-Aug	30-Sep	31-Oct
No Wear
Astroplay	29.0	34.9	32.8
Astroturf	56.4	67.0	65.4
Experimental	35.5	44.0	42.1
Fieldturf	32.3	36.8	33.2
Geoturf	47.2	57.0	55.2
Nexturf	25.3	34.4	34.1
Omnigrass 41	31.6	35.7	35.7
Omnigrass 51	31.8	35.0	35.7
Sofsport	32.2	38.5	37.6
Sprinturf	31.4	37.0	36.9
Wear³
Astroplay	35.4	44.3	40.0
Astroturf	59.1	68.6	61.9
Experimental	35.9	46.5	43.5
Fieldturf	32.7	42.5	38.9
Geoturf	46.0	56.8	53.4
Nexturf	32.6	38.2	33.9
Omnigrass 41	37.3	41.7	39.0
Omnigrass 51	38.6	41.3	38.1
Sofsport	36.2	38.1	37.5
Sprinturf	34.6	41.6	41.5
LSD (p-0.05)	3.5	3.6	41.5

¹Grooming of wear and no wear plots occurred on 9-10 Oct 2003.
²Abrasion index is determined by pulling foam blocks in a weighted sled across the plots in 4 directions and determining the loss (by weight) of the blocks. Abrasiveness index =[(starting block weight - final block weight)/6]*100.
³7 Aug testing performed after wear simulating 44 games. 30 Sep testing performed after wear simulating 88 games. 31 Oct testing performed after wear simulating 92 games.

Table 18. Abrasion index of ten synthetic turf products in 2004 prior to and after grooming¹
Treatment	Abrasion index²
Treatment	9 Jul	26 Aug
No Wear
Astroplay	33.7	33.6
Astroturf	51.5	53.9
Experimental	41.1	38.1
Fieldturf	32.4	32.5
Geoturf	44.6	51.0
Nexturf	30.5	29.3
Omnigrass 41	37.7	35.1
Omnigrass 51	35.6	34.3
Sofsport	33.8	36.1
Sprinturf	38.9	38.6
Wear³
Astroplay	39.0	35.5
Astroturf	50.8	48.8
Experimental	38.8	35.1
Fieldturf	36.2	35.4
Geoturf	43.8	46.3
Nexturf	34.3	29.5
Omnigrass 41	37.7	32.4
Omnigrass 51	41.1	35.9
Sofsport	31.6	36.1
Sprinturf	40.1	37.2
LSD (p=0.05)	10.0	3.4

¹Grooming of wear and no wear plots occurred on 4-5 Aug 2004.
²Abrasion index is determined by pulling foam blocks in a weighted sled across the plots in 4 directions and determining the loss (by weight) of the blocks. Abrasiveness index =[(starting block weight - final block weight)/6]*100.
³9 Jul testing performed after wear simulating 96 games. 26 Aug testing performed after grooming of all plots on 4-5 Aug.

A Survey of Microbial Popluations in Infilled Synthetic Turf Fields

Staphylococcus aureus is a bacterium that is a common inhabitant of human skin and can cause various types of skin or soft tissue infections (Marples, et al, 1990). S. aureus has also been implicated in certain types of food poisoning (Bennet and Lancette, 1998) and in serious medical problems such as toxic shock syndrome. Strains of S. aureus that are resistant to common antibiotics are becoming more common, particularly in medical settings. There have been reports recently of methicillin-resistant S. aureus causing infection in athletes (Begier, et al, 2004). With the increase in athlete infections, there is growing concern regarding the role of infilled turf systems (Seppa, 2005). While there is some indication that the source of these bacteria may be more closely associated with locker room activity than with the infill system (Begier, et al, 2004; Kazakova, et al, 2005), conclusive evidence is not currently available.

The objective of this survey was to determine the microbial population of several infilled synthetic turf systems as well as natural turfgrass fields. In addition, other surfaces from public areas and from an athletic training facility were also sampled. Colonies suspected to be S. aureus were positively or negatively identified.

Materials & Methods

Sample Collection

All samples in this study were collected between June 15 and June 30, 2006. Infilled synthetic turf systems were located at facilities in Pennsylvania and were in use by all levels of play ranging from elementary to professional athletes. Infill material samples were collected from both a 'high use' and a 'low use' area of each field. A 'high use' area typically was a goal mouth or, for a football only field, an area between the 30- and 40-yard lines between the hash marks. A 'low use' area was typically an area toward the edge of the field (but within the field of play) or an end zone. Approximately 2-3 ml of infill material were removed from each area of the field using a sterile test tube inserted directly into the infill. Pile fiber samples were also collected from many fields by clipping several fibers from the backing and transferring the fibers to a sterile test tube. Samples were stored in a cooler and processed as soon after collection as possible.

Sample Processing

Approximately 0.075 g of infill material was transferred to a test tube containing 10 ml sterile 0.1% peptone broth. The sample was agitated for 30 seconds Serial dilutions of each sample were plated up to 10-3 on both R2A agar for total organism populations and Baird-Parker agar, a selective media for Staphylococcus (Bennet and Lancette, 1998). Duplicate platings were made for each media and each dilution. Petri plates were parafilmed and incubated at room temperature and colony counts were made 72 hours after processing. Samples on Baird-Parker agar were also observed again after 5 days. Calculations were then made to determine the number of colony forming units (CFU) per gram of infill material.

For comparison purposes, soil samples were also collected from a native soil and a sand based natural turfgrass athletic field. Samples were processed in the same manner as the infill material samples with 0.2 grams of soil being used for processing.

Sampling of Other Surfaces

Samples were collected from common surfaces in public areas as well as from various surfaces in an athletic training area. Samples were collected by swabbing surfaces with sterile cotton swabs. Random individuals were also tested by swabbing hands and/ or face. Both R2A and Baird-Parker agar plates were wiped with the sterile swabs. Plates were incubated at room temperature and colony counts were conducted after 72 hours for R2A agar and again at 5 days for Baird-Parker media.

Identification of Staphylococcus aureus colonies

Gram stains and latex agglutination tests (Essers and Radebold, 1980) were performed on colonies suspected of being S. aureus. Several potential S. aureus colonies isolated from hand and facial swabs were also included in the testing.

Results and Discussion

Field Samples

The results of total microbial populations are shown in Table 1. While microbes exist in the infill media the number was low compared to natural turfgrass field soils. It should be remembered that microbes tend to be present on most surfaces humans come in contact with and the simple presence of microbes should not be cause for concern. In fact, many products on the market claim to boost the microbial populations of natural turfgrass soils with higher microbial populations considered to be beneficial.

Table 1. Colony forming units (CFU) detected on R2A media per gram of crumb rubber.
Treatment	28-31 Jul 2003					8-12 Sep 2003
Treatment	Gmax¹	HIC²	SI³	Sub temp (°F)⁴	Infill depth (cm)	Gmax	HIC	SI	Sub temp (°F)	Infill depth (cm)
No Wear
Astroplay	75.0	173.5	201.1	78.9	4.2	79.7	183.8	231.3	73.0	4.0
Astroturf	113.3	244.7	293.1	82.2	0.7	102.1	244.0	285.9	78.2	NA
Experimental	81.1	182.2	211.7	76.5	3.6	83.1	195.9	227.9	75.4	3.5
Fieldturf	93.1	203.4	237.2	83.5	4.3	94.4	223.1	259.6	74.8	4.3
Geoturf	101.6	240.2	282.5	96.6	2.8	101.1	234.7	273.7	70.0	3.3
Nexturf	62.1	130.5	152.5	74.7	2.3	70.2	158.2	184.5	80.9	2.2
Omnigrass 41	83.3	198.2	229.7	83.4	4.0	87.7	208.6	241.9	69.2	3.9
Omnigrass 51	72.5	170.2	196.5	78.1	4.9	95.0	234.9	272.6	71.1	4.9
Sofsport	88.8	204.6	238.7	88.4	3.2	105.0	258.1	305.6	72.7	3.3
Sprinturf	101.9	235.3	276.0	79.2	2.6	102.8	236.7	278.7	73.6	2.8
Wear⁵
Astroplay	75.7	174.0	202.2	79.3	4.2	82.1	196.5	227.5	72.0	4.0
Astroturf	109.6	227.1	274.1	81.9	0.7	108.3	258.9	305.0	79.0	NA
Experimental	86.9	207.2	240.3	76.0	3.5	81.1	190.1	221.2	75.4	3.2
Fieldturf	95.3	214.2	250.3	79.2	4.2	95.1	225.5	261.9	75.8	4.2
Geoturf	95.4	217.9	254.5	88.7	3.1	100.6	239.7	279.3	71.3	3.1
Nexturf	64.8	139.4	164.1	75.0	2.2	68.7	152.0	177.6	87.3	1.8
Omnigrass 41	89.0	221.5	256.7	82.7	3.8	93.2	228.9	264.9	69.2	3.7
Omnigrass 51	78.3	193.0	222.8	82.1	4.8	90.9	219.9	255.3	71.7	4.6
Sofsport	88.9	209.8	244.2	86.8	3.1	103.8	252.8	299.7	72.6	3.1
Sprinturf	106.6	253.6	296.7	78.1	2.5	99.2	232.0	273.1	73.2	2.7
LSD (p=0.05)	6.1	24.1	28.0	4.5	0.3	8.0	29.2	33.8	2.5	0.2

Pile fiber samples were also collected from several fields. CFUs for fiber samples range from 200-2933 CFUs per fiber sample (2 fibers approximately 1 cm long) indicating that the fibers alone generally exhibited lower microbial populations compared to the infill.

Microbial colonies isolated from field samples generally included both fungi and bacteria. Some fields had predominantly one organism type while other fields contained a variety of organisms. In order to positively identify the presence of S. aureus , three procedures were used. No colonies isolated from any crumb rubber or fiber samples tested positive for S. aureus via selective media, gram stain or latex agglutination tests.

Other Surfaces

Surfaces other than athletic playing surfaces were tested for the presence of microbes and S. aureus. These surfaces are not granulated and thus the results are listed in Table 2 as total colony number as opposed to CFU per gram of granulated material.

Table 2. Number of colonies per swab detected on R2A media from various sources in public spaces and an athletic training facility.
Treatment	Gmax²
Treatment	4 Aug	27 Aug	20 Nov
No Wear
Astroplay	51.6	52.1	37.2
Astroturf	97.0	99.3	70.9
Experimental	61.6	64.8	41.5
Fieldturf	66.7	65.5	48.1
Geoturf	82.0	84.0	59.6
Nexturf	48.6	51.2	51.4
Omnigrass 41	61.3	62.6	42.9
Omnigrass 51	45.1	48.4	29.7
Sofsport	68.8	69.6	54.1
Sprinturf	86.3	90.2	60.4
Wear³
Astroplay	53.9	58.1	44.0
Astroturf	113.5	118.6	78.5
Experimental	65.3	70.8	47.9
Fieldturf	68.5	78.4	57.4
Geoturf	79.7	83.7	65.3
Nexturf	52.9	53.7	52.3
Omnigrass 41	65.8	70.6	50.4
Omnigrass 51	50.3	53.4	38.8
Sofsport	74.2	78.5	56.4
Sprinturf	93.7	101.2	65.2
LSD (p=0.05)	10.1	10.2	3.5

Table 3. Surfaces that tested positive (+) for *S. aureus* colonies per swab detected.
Treatment	Severity Index²		Head Injury Criterion²
Treatment	4 Aug	27 Aug	4 Aug	27 Aug
No Wear
Astroplay	93.7	97.6	80.2	82.1
Astroturf	254.6	261.6	217.9	224.0
Experimental	130.6	137.5	112.5	118.4
Fieldturf	147.9	140.8	128.3	121.9
Geoturf	196.4	204.0	169.1	175.8
Nexturf	102.3	105.1	86.5	91.5
Omnigrass 41	131.9	135.1	113.5	116.3
Omnigrass 51	78.9	86.8	66.3	74.1
Sofsport	159.2	161.9	137.5	140.2
Sprinturf	207.3	220.3	177.7	189.4
Wear³
Astroplay	104.6	122.3	90.3	105.8
Astroturf	314.1	327.1	265.8	275.4
Experimental	140.9	162.6	121.0	139.8
Fieldturf	152.6	190.0	132.3	164.6
Geoturf	189.9	207.5	163.5	178.8
Nexturf	111.1	114.2	96.5	100.3
Omnigrass 41	150.9	166.9	130.2	143.8
Omnigrass 51	101.7	111.3	88.3	96.6
Sofsport	180.9	195.4	156.2	168.4
Sprinturf	231.4	256.2	197.4	218.3
LSD (p=0.05)	21.3	37.4	18.4	31.4

¹Grooming of wear and no wear plots occured on 9-10 Oct 2003.
²Severity Index and Head Injury Criterion were measured using a Clegg Impact Tester equipped with a 2.25 kg hammer.
³4 Aug testing performed on 4 Aug after wear simulating 44 games. 27 Aug testing performed after wear simulating 84 games.

Microbial colonies isolated from surfaces included a mixture of fungi and bacteria. Colonies from the trash can were predominantly fungi. While not specifically identified, all colonies from the sauna swab appeared to be the same. S. aureus was positively identified from several samples including towels, blocking pads, weight equipment, and the stretching table. In addition, S. aureus was positively identified from every facial and hand swabs tested.

References

Baird-Parker, AC. 1990. The staphylococci: an introduction. Pg 1S-8S In: Journal of Applied Bacteriology Symposium Supplement Series 19. D. Jones, R G Board, and M Sussman, ed. Blackwell Scientific Publications. Oxford.
Begier, E.M., K. Frenette, N.L. Barrett, P. Mshar, S. Petit, D.J. Boxrud, K Watkins-Colwell, S. Wheeler, E.A. Cebelinski, A. Glennen, D. Nguyen, and J.L. Hadler. 2004. A high-morbidity outbreak of methicillin-resistant Staphylococcus aureus among players on a college football team, facilitated by cosmetic body shaving and turf burns. Clin Infect Dis 39: 1446-1453.
Bennet, R.W. and G.A. Lancette. 1998. Bacteriological Analytical Manual, 8th Edition, Revision A. Chapter 12.
Essers, L. and K. Radebold. 1980. Rapid and reliable identification of Staphylococcus aureus by a latex agglutination test. J. Clin. Microbiol. 12:641-643.
Kazakova, S.V., J.C. Hageman, M. Matava, A. Srinivasan, L. Phelan, B. Garfinkel, T. Boo, S. McAllister, J. Anderson, B. Jensen, D. Dodson, D. Lonsway, L.K. McDougal, M. Arduino, V.J. Fraser, G. Killfore, F.C. Tenover, S. Cody, and D.B. Jernigan. 2005. A clone of methicillin-resistant Staphylococcus aureus among professional football players. NEJM 352:468-475.
Marples, R.R., J.F. Richardson, and F.E. Newton. 1990. Staphylococci as part of the normal flora of human skin. Pg 93S-99S In: Journal of Applied Bacteriology Symposium Supplement Series 19: Staphylococci. D. Jones, R G Board, and M Sussman, ed. Blackwell Scientific Publications. Oxford.
McNitt, A.S. 2005. Synthetic Turf in the USA -- Trends and Issues. Int. Turfgrass Soc. Res. J. 10:27-33.
Seppa, N. 2005. There's the rub: Football abrasions can lead to nasty infections. Science News 167: 85-86.

Temperature and Color

Temperature

Researchers have found that the surface temperatures of synthetic turf playing surfaces are significantly higher than natural turfgrass surfaces when exposed to sunlight. (Buskirk et al., 1971; Koon et al., 1971; and Kandelin et al. 1976). Buskirk et al. (1971) found that the surface temperatures of traditional synthetic turf were as much as 35-60 °C higher than natural turfgrass surface temperatures. Buskirk et al. (1971) placed thermocouples on the inner soles of cleated shoes and had individuals walk on the synthetic surface to determine the amount of heat transferred directly from the surface to the individual's foot. Any heat gain to the foot must be dissipated by blood flow. Buskirk et al. (1971) concluded that the heat transfer from the surface to the sole of an athlete's foot was significant enough to contribute to greater physiological stress that may result in serious heat related health problems.

Surface temperatures of infill synthetic turf systems have been reported to be as high as 93°C on a day when air temperatures were 37°C (Brakeman, 2004). Researchers at Brigham Young University measured the surface and air temperature above an infill synthetic turf system before and for a period of time after water had been applied through irrigation (Brakeman, 2004). The researchers reported that after 30 minutes of irrigation the surface temperature was lowered to that of a nearby natural turfgrass surface (29°C). However, the researchers reported that the surface temperature rose very quickly and within 5 minutes had risen to 49°C. This rapid rise in temperature could be due to the lack of through wetting of the infill media, which was found to be hydrophobic. This author personally observed this field on 19 May 2004. The infill media was very hydrophobic and water was observed to bead-up and run over the surface rather than penetrate. After a 10-minute irrigation cycle, water was observed to be moving laterally over the surface while the infill media was only wet to an average depth of 1 - 2 mm. The use of a non-ionic wetting agent may help to alleviate this problem.

Morehouse (1992) suggests that the evaporation of 1.2 L m ^-2 h ^-1 of water should be sufficient to cool a traditional synthetic surface to a level near that of a natural turfgrass surface and notes that water routinely applied to synthetic surfaces, used for women's field hockey to slow ball bounce, will dampen the surface for at least one-half game even under favorable evaporative conditions (i.e. elevated air temperature and brisk air movement). The amount of water suggested for application prior to a field hockey event is 8,000 to 10,000 L spread evenly across a 105 m x 64 m surface. In our current study, we have observed that after equal quantities of irrigation were applied to the treatment plots, the traditional synthetic turf (Astroturf) remained damp for a longer period of time than nine infill synthetic turf systems. These results indicate that the formula Morehouse (1992) suggested for water application to traditional synthetic turf may not be applicable to infill systems.

We tried to measure the temperature of the synthetic turf surfaces on clear bright days. In central Pennsylvania they are sometimes few and far between. We measured both air and surface temperature using an infrared thermometer (Scheduler Model 2 LiCor Corporation) (Fig. 27).

The temperature results are shown in Tables 19, 20A, and 20B. Some surfaces registered slightly higher in surface temperature compared to others although we found few meaningful air temperature differences three feet above the surfaces.

Table 19. Surface temperature of ten synthetic turf products in 2003.
Treatment	Surface temperature (°F)¹	Air temperature (°F)²
No Wear
Astroplay	116.2	78.1
Astroturf	125.4	78.6
Experimental	119.1	76.6
Fieldturf	116.2	79.0
Geoturf	127.6	79.7
Nexturf	124.0	77.2
Omnigrass 41	118.6	78.6
Omnigrass 51	120.6	79.3
Sofsport	121.8	80.6
Sprinturf	113.7	79.5
Wear³
Astroplay	111.4	78.1
Astroturf	125.2	79.0
Experimental	117.9	77.2
Fieldturf	120.2	79.2
Geoturf	124.7	79.2
Nexturf	122.5	76.3
Omnigrass 41	115.3	78.8
Omnigrass 51	118.2	79.7
Sofsport	120.9	79.5
Sprinturf	107.6	79.9

¹Surface temperature was measured on 7 Sep 2003 using a LiCor Scheduler infrared thermometer.
²Air temperature was measured approximately three feet above synthetic turf surface at the same time surface temperature was measured.
³Plots exposed to wear simulating 88 games at the time of data collection.

Table 20A. Surface and air temperatures (C)¹ of ten synthetic turf products measured at 3 dates in 2003 and 2004.
Product	7 Sep 03		30 Jun 04		3 Aug 04
Product	Surface	Air²	Surface	Air	Surface	Air
Astroplay	46.8	25.6	51.9	25.7	59.5	30.5
Astroturf	51.9	25.9	52.4	25.5	53.8	28.9
Experimental	48.4	24.8	52.3	26.1	58.4	30.8
Fieldturf	46.8	26.1	58.1	25.6	64.8	28.3
Geoturf	53.1	26.5	61.1	25.9	70.8	29.5
Nexturf	51.1	25.1	56.4	25.1	71.5	30.6
Omnigrass 41	48.1	25.9	53.2	25.8	64.2	29.3
Omnigrass 51	49.2	26.3	55.6	25.6	63.1	29.4
Sofsport	49.9	27.0	54.6	25.5	62.6	29.1
Sprinturf	45.4	26.4	48.1	25.8	54.4	30.0

¹Temperatures were measured using a LiCor Scheduler infrared thermometer.
²Air temperature was measured approximately three feet above the synthetic turf surface at the same time surface temperature was measured.

Table 20B. Surface and air temperatures (F)¹ of ten synthetic turf products measured at 3 dates in 2003 and 2004.
Product	7 Sep 03		30 Jun 04		3 Aug 04
Product	Surface	Air²	Surface	Air	Surface	Air
Astroplay	116.2	78.1	125.4	78.3	139.1	86.9
Astroturf	125.4	78.6	126.3	77.9	128.8	84.0
Experimental	119.1	76.6	126.1	79.0	137.1	87.4
Fieldturf	116.2	79.0	136.6	78.1	148.6	82.9
Geoturf	127.6	79.7	142.0	78.6	159.4	85.1
Nexturf	124.0	77.4	133.5	77.2	160.7	87.1
Omnigrass 41	118.6	78.6	127.8	78.4	147.6	84.7
Omnigrass 51	120.6	79.3	132.1	78.1	145.6	84.9
Sofsport	121.8	80.6	130.1	77.9	144.7	84.4
Sprinturf	113.7	79.5	118.6	78.4	129.9	86.0

During 2004 and in 2005 we evaluated the effect of irrigation on surface temperatures. Approximatly 0.5 inches of water was applied during irrigation. The application of water significantly lowered the surface temperatures of all synthetic surfaces (Fig. 28 and 29). The temperatures rebounded somewhat after 15 minutes and then remained relatively stable for 90 and 210 minutes, respectively. There were intermittent cumulus clouds during the rating period for these days. The effect of the passing clouds can be seen in the erratic nature of the data especially at the 2 Aug 04 rating date. For this reason, we've included data from our first rating date in 2005 (Fig. 30) that was collected on a very clear day. Air temperatures were not as high as the previous rating dates. We began collecting data on 2 Jun 05 at 11:15 am. Air temperature was 73°F with 39% relative humidity and wind speed was 4-5 mph. Data collection ended at about 3:15 pm at which time air temperature was 80°F with 33% relative humididty and wind speed at 4-5 mph. Because of the almost complete lack of cloud cover, we have more confidence in the 2005 results.

Figure 28. Surface temperatures of synthetic turf plots during and after an irrigation event on 30 June 04

Figure 29. Surface temperatures of synthetic turf plots during and after an irrigation event on 3 August 04.

Figure 30. Surface temperatures of synthetic turf plots during and after an irrigation event on 2 June 05.

Irrigation again resulted in a reduction of surface temperatures for the 195 minutes measured. At the end of the experiment the surface temperatures of the irrigated plots averaged 14 degrees lower than the non-irrigated plots. The Astroturf treatment had the highest pre-irrigation temperature and consistently measured lowest in post-irrigation temperature. This trend can be observed in the 2004 data.

Temperature of a synthetic surface will depend on numerous variables. The benefit of surface cooling through irrigation may vary depending on conditions. Irrigation systems on synthetic fields have other benefits such as reduction of wear by allowing the field manager to broom the surface when wet and wash in fabric softeners and/or wetting agents. More temperature data is being collected and this report will be updated.

Color

In order to determine the amount of matting that is occurring, color readings of the surfaces were recorded on the no wear plots at installation and on the wear plots just prior to grooming on 8 Oct 2003 using a Model CR-310 chromameter (Minolta Co, Ltd, Ramsey, NJ) (Fig. 31). The two measurements should provide the extremes of matting and by measuring color weekly during 2004 we should be able to produce a matting index.

Color data is shown in Table 21. Color data is being collected in an attempt to develop a measure of 'matting' or how much the pile lays over after simulated traffic. We measured color of the wear and no wear plots just before and just after grooming. We had hoped that these measurements would define the spectrum of color differences due to matting. We are not satisfied that this method accurately measures the amount of matting. Currently, we are unaware of an accepted method to quantitatively evaluate matting other than visual ratings.

Table 21. Color (lightness, chroma, and hue angle) of ten synthetic turf products determined in 2003 by the Minolta CR-310 Chroma Meter prior to and after grooming¹
Treatment	7 October			23 October
Treatment	Lightness²	Chroma³	Hue angle⁴	Lightness	Chroma	Hue angle
No Wear
Astroplay	25.2	17.0	125.7	26.6	17.7	127.1
Astroturf	33.2	18.4	156.8	33.5	18.7	157.8
Experimental	30.9	17.1	127.5	29.5	17.3	129.2
Fieldturf	28.3	16.7	126.8	28.3	17.7	127.5
Geoturf	29.8	16.5	128.9	30.5	17.4	130.3
Nexturf	25.0	14.5	128.2	25.1	15.4	130.0
Omnigrass 41	28.4	17.6	112.7	28.8	19.4	114.4
Omnigrass 51	28.1	18.3	112.5	27.8	18.6	114.8
Sofsport	30.8	17.4	127.6	30.3	17.8	129.1
Sprinturf	28.5	19.4	126.3	28.7	20.3	127.7
Wear⁵
Astroplay	31.7	15.4	125.5	30.5	17.2	127.2
Astroturf	33.1	17.5	157.3	33.6	18.5	157.4
Experimental	33.3	16.2	127.2	32.1	17.6	128.7
Fieldturf	31.6	16.4	126.8	31.8	17.7	127.3
Geoturf	30.5	15.6	129.2	30.2	17.0	130.4
Nexturf	28.2	15.4	127.3	27.0	15.3	128.2
Omnigrass 41	34.6	18.3	112.0	35.2	20.3	113.6
Omnigrass 51	36.1	18.2	112.3	34.8	20.9	114.1
Sofsport	32.8	16.7	127.5	30.9	18.2	128.5
Sprinturf	33.0	19.5	126.0	31.1	20.3	127.2
LSD (p=0.05)	1.7	1.2	0.7	1.2	1.3	0.8

¹Grooming of wear and no wear plots occured on 9-10 Oct 2003.
²Expressed on a scale of 0 = black to 100 = white.
³Expressed on a scale of 0 = gray to 60.
⁴Hue angles of the four primary colors are red, 0°; yellow, 90°; green, 180°; and blue, 270°.
⁵7 Oct and 23 Oct testing were performed after wear simulating 92 games.

Table 22. Color (lightness, chroma, and hue angle) of ten synthetic turf products determined in 2004 by the Minolta CR-310 Chroma Meter prior to and after grooming¹.
Treatment	28 July			10 August
Treatment	Lightness²	Chroma³	Hue angle⁴	Lightness	Chroma	Hue angle
No Wear
Astroplay	28.8	18.1	125.3	29.1	17.0	124.5
Astroturf	29.4	17.5	157.5	32.8	18.4	157.5
Experimental	31.6	16.8	127.0	30.8	16.1	126.8
Fieldturf	30.6	17.1	126.3	29.2	17.4	125.7
Geoturf	30.3	16.3	128.7	30.8	15.8	127.1
Nexturf	26.5	15.2	128.0	27.0	14.9	125.9
Omnigrass 41	31.1	18.9	112.2	31.4	18.8	110.3
Omnigrass 51	31.0	18.9	111.7	31.5	18.6	110.3
Sofsport	31.2	17.3	127.8	31.3	17.6	126.7
Sprinturf	30.7	18.8	125.2	31.0	19.1	124.8
Wear⁵
Astroplay	33.0	15.9	124.8	31.0	15.7	124.3
Astroturf	28.7	17.5	157.0	33.8	17.3	156.6
Experimental	33.4	16.2	126.7	32.9	16.5	126.3
Fieldturf	33.1	16.1	126.6	31.5	16.6	125.7
Geoturf	31.3	15.8	128.4	30.9	15.8	127.0
Nexturf	26.9	14.7	126.8	26.4	14.1	125.7
Omnigrass 41	35.9	18.0	111.6	34.8	18.2	110.0
Omnigrass 51	36.4	18.3	111.3	34.5	18.3	109.7
Sofsport	31.7	16.6	127.3	31.0	16.6	126.4
Sprinturf	31.5	18.1	125.3	31.5	17.1	124.6
LSD (p=0.05)	1.2	1.1	1.1	1.5	1.2	0.5

¹Grooming of wear and no wear plots occured on 4-5 Aug 2004.
²Expressed on a scale of 0 = black to 100 = white.
³Expressed on a scale of 0 = gray to 60.
⁴Hue angles of the four primary colors are red, 0°; yellow, 90°; green, 180°; and blue, 270°.
⁵28 Jul and 10 Aug testing were performed after wear simulating 92 games.

Summary and Considerations

It should be remembered that the data posted in this report is from the first two years of a long term study. To this point the systems are performing very well. The infill systems are softer, less abrasive, and generally exhibit better traction qualities than traditional Astroturf. They maintained these qualities after 180 plus games of simulated traffic. The Gmax and traction values obtained from the synthetic surfaces are very comparable and in some cases more desirable than those measured on a similarly worn natural turfgrass area.

A review of current literature regarding safety and playability of infill synthetic turf systems can be found in the Athlete Performance and Safety section of this website. For the results of a survey of microbial populations in synthetic turf, please refer to A Survey of Microbial Populations in Infilled Synthetic Turf Fields found on this site.

Some things to consider when budgeting for an infilled synthetic turf system:

Poor surface grading and lack of internal drainage are the two main construction problems encountered in infill synthetic turf systems in the USA. Currently, there are no standard specifications for drainage gravel installed beneath the backing of an infill system. The lack of an agreed upon standard has resulted in numerous installations with poor quality gravel that is either hard to grade to desired tolerances or that allows little internal drainage after compaction. The Synthetic Turf Council was formed in 2002 in order to produce a set of minimum specifications that will protect consumers from installations of poor quality synthetic turf infill systems (Synthetic Turf Council Inc., 2003). Currently, the council specifies that the sub-base drainage gravel of a synthetic turf field should provide adequate drainage and stability; however, a gravel particle size distribution is not specified. Subcommittees within the Synthetic Turf Council and in the F.08 division of ASTM are currently working on sub-base gravel specifications. The following link is to a set of specifications that have worked well. Gravel Drainage Specifications. By no means does this suggest that other drainage aggregates that do not meet this specification will cause drainage failure. They are listed here only as a guide. University and private labs can test drainage material to make sure they have sufficient permeability after compaction. After suitable materials are located, a quality control program during shipping is strongly suggested. The specifications provided are based on the specifications for drainage beneath a USGA golf green. These specifications suggest quality control testing of the gravel every 500 tons.
For heavily used fields, such as a high school where there is at least one sporting event per day, you should plan to broom the field weekly. This is done to keep the pile somewhat upright. This is different from grooming where the granules are loosened. Brooming can be accomplished by dragging a set of tennis court brooms or a piece of traditional Astroturf turned upside down across the field in varying directions. To reduce abrasion due to brooming, drag the tennis court brooms or Astroturf when the field is wet. Do not use a power broom weekly as this aggressive brooming will increase wear to the pile fiber due to abrasion.
Grooming or loosening of the infill granules should be done at least once or twice per year. See the section on simulated foot traffic and grooming for details. Most field managers that we've talked to do not like the spring tine method of loosening infill because they feel it is too aggressive. Most like the star shaped unpowered slicer that we used (Fig. 32) and suggest a similar but larger model for field use. (Fig.33) See simulated foot traffic and grooming for details. Currently we suggest loosening the granules twice per year.
Figure 32 and 33
The fields do get hot on sunny days. Some organizations have installed irrigation systems to reduce the heat. These fields warm up fast on clear sunny days but also cool down rapidly when the sun is not shining; there doesn't seem to be much of a heat sink. Irrigation of these fields dramatically reduce the surface temperature; however, in our limited testing we have found that a dramatic reduction in temperature is short term. Irrigation resulted in an average 15 degree F decrease in surface temperature for 200 minutes in our conditions. While irrigation may have a dramatic affect on surface temperature for a limited time and a limited effect over a longer time, it may prove beneficial in other respects such as washing in fabric softeners and wetting agents. Irrigation would also be beneficial in wetting the surface prior to brooming to reduce abrasive wear on the pile fibers. While these surfaces are hotter than natural turfgrass, the temperatures measured in this study of non-irrigated surfaces do not exceed traditional synthetic turf (Astroturf) that has been in use since the 1960s.
There is a static build up on these surfaces, at least in year one when the fields are new. The only problem that I see with the static is aesthetic. The black granules tend to stick to the upright pile fibers and the field will temporarily look darker in high wear areas. The application of very dilute fabric softener will reduce this problem and has become a standard practice for some field managers. We have no data on the use of fabric softeners and their effect on playability. Some field managers have expressed their opinion that if fabric softener is used, it should be sprayed several days prior to an event as the material can make the field slippery if applied just prior to a game. Static tends to be a problem only with new systems. As the systems age the static is reduced; however, a new problem can arise--hydrophobicity. The granulated infill media in many systems can become hydrophobic. Precipitation will 'beadup' and roll off the surface rather than penetrate. An application of a wetting agent or surfactant may be required to maintain permeability over time. The effectiveness of wetting agents for this application has not been tested but in theory they should reduce the hydrophobicity of the infill media.
The long-term durability of these fields is unknown. The duration of the warranties offered by synthetic turf companies has been set by economic and competitive issues as opposed to knowledge of the long-term durability of the systems. Originally, the standard warranty of a crumb rubber infill synthetic turf system was five years. Competition increased the warranty to eight years and for several projects the systems were warranted for 10 years. Currently, an eight-year warranty is considered standard in the United States. This author has seen some outdoor high-use fields that may last well beyond the warranty period while others look worn after only one year of use. Since the pile fibers breakdown due to both foot traffic and photodegradation, indoor fields will typically outlast fields that are exposed to sunlight. The author has observed thinning pile fiber in high wear areas around the goal mouth of high school lacrosse fields after only two years of use. There is no standard method to evaluate wear or thinning of the pile fiber. A warranty providing a guarantee against 'excessive wear' is open to interpretation.

The Synthetic Turf Council (Daulton, GA) is a non-profit organization formed to set minimum quality standards for synthetic turf manufacturing and use in the United States. The council is currently wrestling with the issue of warranty duration and is considering suggesting some guidelines on system warranties (Synthetic Turf Council, Inc., 2003). Of critical importance to the consumer when trying to select an infill system is to consider whether that company will still be in business throughout the duration of the warranty. Some of the companies representing an infill synthetic turf system have already gone out of business in the United States. Of considerable note was the closure of SRI, Inc., owner and manufacturer of AstroTurf, AstroPlay, and NeXturf. From the 1970's through much of the 1990's this company was the largest manufacturer and installer of synthetic turf systems in the United States.

In the bid contract:

Demand that the surface company pay for independent Gmax testing yearly for the length of warranty.
Negotiate a maximum acceptable Gmax level lower than 200 (175 suggested)
Demand good quality grooming equipment be provided.
You'll also need a utility cart to pull the grooming equipment.

In conclusion we've made progress establishing testing methods for evaluation of these surfaces. This will allow us to more collect data more rapidly in the coming years. The infill systems generally outperformed traditional Astroturf in playing quality. The playing quality of these systems remained high after rather intense simulated traffic was applied. The playing quality of the infilled systems increased after brooming and grooming.

Bibliography and Acknowledgements

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American Society for Testing and Materials. 2000b. Annual Book of ASTM Standards. Vol. 15.07. End Use Products. Standard Test Method for Shock-Attenuation Characteristics of Natural Playing Surface Systems Using Lightweight Portable Apparatus. F1702-96. ASTM, West Conshohocken, PA.
American Society for Testing and Materials. 2000c. Annual Book of ASTM Standards. Vol. 15.07. End Use Products. Proposed Standard Test Method for Traction Characteristics of the Athletic Shoe - Sports Surface Interface. Work Number 486. ASTM, West Conshohocken, PA.
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Acknowledgements

The researchers for this project would like to thank the following companies and organizations for their support. Without their continued support this project would be impossible to complete.

Athlete Performance and Safety

Numerous studies have been conducted to evaluate the safety and playability of traditional (non-infill) synthetic turf surfaces. Three methodologies are used to compare the safety and performance of various surfaces. These include 1) material tests where mechanical devices simulate human movement and measure the associated forces; 2) human performance tests where researchers measure the forces associated with the interaction of a human subject and a surface; and 3) epidemiological studies in which the number and type of injuries sustained by athletes during actual sporting events are counted.

Material tests have been completed that measure the shoe-surface traction and surface hardness of synthetic turf surfaces (Bowers and Martin, 1975; McNitt and Petrunak, 2001; Valiant, 1990). Human subject tests have shown improved athlete performance on traditional synthetic turf when compared to natural turfgrass (Krahenbuhl, 1974; Morehouse and Morrison, 1975) and epidemiological studies have counted the number of knee and ankle injuries on synthetic versus natural turfgrass (Meyers and Barnhill, 2004; Powell and Schootman, 1992; Powell and Schootman, 1993).

No large-scale epidemiological studies have been published comparing the number of surface-related injures sustained by athletes playing on infill synthetic turf systems to the number of injures sustained on either traditional synthetic turf or natural turfgrass surfaces. One study (Meyers and Barnhill, 2004) compared injury incidence of eight high school (American) football teams in Texas USA playing on infilled synthetic surfaces (FieldTurf) and natural turfgrass surfaces. Although similarities in injury occurrence existed between FieldTurf and natural grass fields over a five-year period of competitive play, there were significant differences in injury time loss, injury mechanism, anatomical location of injury, and type of tissue injured between playing surfaces. The researchers reported higher incidences of 0-day time loss injuries, noncontact injuries, surface/epidermal injuries, muscle-related trauma, and injuries during higher temperatures on FieldTurf compared to natural turfgrass surfaces. Higher incidences of 1- to 2-day time loss injuries, 22+ day time loss injuries, head and neural trauma, and ligament injuries were recorded on natural turfgrass fields compared to FieldTurf. The researchers state a number of limitations to their study including the random variation in injury typically observed in high-collision team sports and the percentage of influence from risk factors, other than simply surface type. Field conditions at the time of injury were not measured although the researchers noted that the majority of injuries (84.4%) occurred on natural turfgrass surfaces under conditions of no precipitation (dry surface).

The United States National Collegiate Athletic Association (NCAA) is collecting injury data from numerous men's and women's sporting events across the United States using a computerized system called " NCAA Injury Surveillance System" (National Collegiate Athletic Association, 2004) but presently does not have sufficient data from which to draw conclusions (R. Dick, 2004, personal communication).

Stefanyshyn et al. (2002) used human performance comparisons to evaluate 20 configurations of infill synthetic turf systems. Human subjects performed various maneuvers on the surfaces and the forces associated with the cleated foot interacting with the surface were recorded in the laboratory using a force plate installed beneath the turf surface. Stefanyshyn et al. (2002) reported a significant range of traction and surface hardness differences among the infill synthetic surfaces (Table 1) and grouped the 20 infill surfaces into categories of highly recommended, recommended, and not recommended based on surface hardness and both the rotational and translational (linear) traction recorded on these surfaces.

Shorten et al. (2003) performed material tests in which weighted shoes were dragged across varying infill synthetic turf systems and traditional synthetic turf. The translational and rotational traction of the various shoe-surface combinations were measured. The researchers concluded that both shoes and surfaces significantly affect traction. On all surfaces tested, shoes with lower profile cleats or studs had better overall traction performance compared to shoes with longer cleats and infill systems had better traction performance than traditional synthetic turf. Traction performance was calculated using an index where rotational traction values were subtracted from translational traction values. To eliminate scaling and range differences between the translational and rotational resistance measures, calculations were done using "standard scores" rather than raw data. The standard score is a measure of where a particular result lies relative to the average and distribution of all the results recorded: ex. Standard Score = (Actual Score − Average Score) / (Standard Deviation of All Scores). The researchers stated that further research is required to determine the effects of moisture, temperature and aging on surface traction performance. Both the study by Stefanyshyn et al. (2002) and the study by Shorten et al. (2003) were performed on newly constructed infill systems in a laboratory setting.

By Andrew McNitt and Dianne Petrunak

Gravel Drainage Specifications

Selection and Placement of Materials When the Intermediate Layer Is Used

The tables above describe the particle size requirements of the gravel and the intermediate layer material.

The intermediate layer shall be spread to a uniform thickness of two to four inches (50 to 100 mm) over the gravel drainage blanket (e.g., if a 3-inch depth is selected, the material shall be kept at that depth across the entire area), and the surface shall conform to the contours of the proposed finished grade.

Selection of Gravel

Selection of this gravel is based on the particle size distribution of the intermediate layer material. The construction superintendent must work closely with the soil testing laboratory in selecting the appropriate gravel. Either of the following two methods may be used:

Send samples of different gravel materials to the lab when submitting samples of components for the intermediate layer material. As a general guideline, look for gravel in the 2 mm to 9.5 mm range. The lab first will determine the best intermediate layer material, and then will test the gravel samples to determine if any meet the guidelines outlined below.

Submit samples of the components for intermediate layer material, and ask the laboratory to provide a description, based on the intermediate layer material tests, of the particle size distribution required of the gravel. Use the description to locate one or more appropriate gravel materials, and submit them to the laboratory for confirmation.

It is not necessary to understand the details of these recommendations; the key is to work closely with the soil testing laboratory in selecting the gravel. Strict adherence to these criteria is imperative; failure to follow these guidelines could result in drainage failure.

The criteria are based on engineering principles which rely on the largest 15% of the root zone particles "bridging" with the smallest 15% of the gravel particles. Smaller voids are produced, and they prevent migration of root zone particles into the gravel yet maintain adequate permeability. The D85 (root zone) is defined as the particle diameter below which 85% of the soil particles (by weight) are smaller. The D15 (gravel) is defined as the particle diameter below which 15% of the gravel particles (by weight) are smaller.

For bridging to occur, the D15 (gravel) must be less than or equal to eight times the D85 (root zone).
To maintain adequate permeability across the root zone/gravel interface, the D15 (gravel) shall be greater than or equal to five times the D15 (root zone).
The gravel shall have a uniformity coefficient (Gravel D90/Gravel D15) of less than or equal to 3.0.

Furthermore, any gravel selected shall have 100% passing a ½" (12 mm) sieve and not more than 10% passing a No. 10 (2 mm) sieve, including not more than 5% passing a No. 18 (1 mm) sieve.

2005-2006 Abrasion Data

Abrasion index of ten synthetic turf products prior to and after grooming.¹
Treatment	Abrasion Index²
	2005		2006
	4 August	7-8 September	6 July	21 September
No Wear
Astroplay	37.4	36.9	NR	NR
Astroturf	57.4	60.2	54.8	60.1
Experimental	46.7	44.0	NR	NR
Fieldturf	36.0	36.2	39.9	38.9
Geoturf	52.0	54.1	NR	NR
Nexturf	36.1	38.7	NR	NR
Omnigrass 41	38.4	38.6	40.8	41.1
Omnigrass 51	34.6	36.7	38.0	40.6
Sofsport	40.0	37.1	42.8	45.2
Sprintturf	40.5	43.3	47.2	52.7
Wear³
Astroplay	36.3	35.0	NR	NR
Astroturf	53.4	59.2	48.2	53.4
Experimental	42.7	40.4	NR	NR
Fieldturf	36.1	38.4	39.5	39.8
Geoturf	45.3	43.6	NR	NR
Nexturf	36.5	38.8	NR	NR
Omnigrass 41	39.2	38.9	43.4	43.6
Omnigrass 51	37.1	37.3	41.7	40.6
Sofsport	37.3	33.0	39.6	42.2
Sprintturf	36.1	37.3	39.2	45.0
LSD (p=0.05)	0.9	1.2	3.7	3.0

¹In 2005, grooming of wear and no wear plots occurred on 5 Aug and 9 Aug 2005. In 2006, grooming of wear and no wear plots occurred on 23-24 Aug 2006.
²Abrasion index is determined by pulling foam blocks in a weighted sled across the plots in 4 directions and determining the loss (by weight) of the blocks. Abrasiveness index =[(starting block weight - final block weight)/6] *100.
³Aug testing performed after wear simulating 96 games. 7-8 Sep testing performed after grooming of all plots on 5 and 9 Aug 2005. 6 Jul testing performed after wear simulating 108 games. 21 Sep testing performed after grooming of all plots on 23-24 Aug 2006.
NR = Not Rated in 2006.

2005-2006 Translational Traction Data


Treatment	2005				2006
	2 August		25 August		16 August		7 August
	Static²	Dynamic³	Static	Dynamic	Static²	Dynamic³	Static	Dynamic
No Wear
Astroplay	1.34	1.14	1.31	1.15	NR	NR	NR	NR
Astroturf	1.51	1.34	1.64	1.38	1.61	1.35	1.55	1.34
Experimental	1.36	1.05	1.41	1.08	NR	NR	NR	NR
Fieldturf	1.45	1.17	1.37	1.13	1.47	1.26	1.47	1.22
Geoturf	1.36	1.26	1.31	1.23	NR	NR	NR	NR
Nexturf	1.43	1.19	1.39	1.17	NR	NR	NR	NR
Omnigrass 41	1.40	1.13	1.39	1.15	1.48	1.24	1.48	1.21
Omnigrass 51	1.36	1.19	1.32	1.11	1.44	1.20	1.48	1.31
Sofsport	1.36	1.15	1.35	1.14	1.48	1.26	1.46	1.25
Sprintturf	1.29	1.11	1.31	1.09	1.39	1.19	1.38	1.18
Wear⁴
Astroplay	1.43	1.23	1.42	1.21	NR	NR	NR	NR
Astroturf	1.69	1.50	1.69	1.47	1.54	1.29	1.44	1.09
Experimental	1.41	1.18	1.37	1.15	NR	NR	NR	NR
Fieldturf	1.46	1.21	1.39	1.16	1.49	1.32	1.50	1.28
Geoturf	1.33	1.19	1.29	1.14	NR	NR	NR	NR
Nexturf	1.44	1.17	1.39	1.16	NR	NR	NR	NR
Omnigrass 41	1.49	1.15	1.45	1.09	1.50	1.22	1.51	1.23
Omnigrass 51	1.43	1.18	1.38	1.15	1.47	1.26	1.50	1.30
Sofsport	1.43	1.24	1.38	1.16	1.45	1.19	1.42	1.17
Sprintturf	1.32	1.19	1.30	1.12	1.38	1.19	1.38	1.15
LSD (p=0.05)	0.09	0.05	0.09	0.06	0.10	0.07	0.10	0.08

¹In 2005, grooming of wear and no wear plots occurred on 5 and 9 Aug 2005. In 2006, grooming of wear and no wear plots occurred on 23-24 Aug 2006.
²Static traction = peak amount of force (N) that is normal to the playing surface.
³Dynamic traction = amount of force (N) to maintain linear motion of footwear/amount of force (N) that is normal to the playing surface.
⁴2 August testing performed after wear simulating 96 games. 25 August testing performed after grooming of the plots on 5 and 9 August 2005. 16 August testing performed after wear simulating 108 games. 7 September testing performed after grooming of the plots on 23-24 August 2006.
NR = Not Rated in 2006.

2005-2006 Rotational Traction Data

Rotational traction determined by ASTM traction standard using 237 pounds of vertical force prior to and after grooming.¹
Treatment	Rotational traction (nm)²
	2005		2006
	3 August	26 August	17 August	1 September
No Wear
Astroplay	38.2	40.1	NR	NR
Astroturf	46.2	47.4	43.2	55.7
Experimental	37.8	41.1	NR	NR
Fieldturf	38.1	42.9	37.1	45.1
Geoturf	42.7	42.3	NR	NR
Nexturf	44.8	47.1	NR	NR
Omnigrass 41	36.8	42.1	34.1	44.7
Omnigrass 51	36.7	41.0	35.9	44.6
Sofsport	38.7	41.3	37.2	46.8
Sprintturf	37.1	41.3	38.4	46.7
Wear³
Astroplay	37.7	40.8	NR	NR
Astroturf	44.6	54.5	45.5	57.6
Experimental	37.2	41.2	NR	NR
Fieldturf	38.8	47.5	42.7	50.0
Geoturf	44.3	46.4	NR	NR
Nexturf	43.9	45.9	NR	NR
Omnigrass 41	37.0	42.1	38.2	47.7
Omnigrass 51	36.4	40.6	36.7	44.2
Sofsport	38.3	47.1	40.2	49.7
Sprintturf	36.7	44.0	37.3	45.4
LSD (p=0.05)	4.4	4.6	3.2	4.4

¹In 2005, grooming of wear and no wear plots occurred on 5 and 9 August 2005. In 2006, grooming of wear and no wear plots occurred on 23-24 August 2006.
²Rotational traction.
³August testing performed after wear simulating 96 games. 26 August testing performed after grooming of the plots on 5 and 9 August 2005. 17 August testing performed after wear simulating 108 games. 1 September testing performed after grooming of the plots on 23-24 August 2006.
NR = Not rated in 2006.

2005-2006 Surface Hardness (Gmax) Measured via ASTM Standard F1702

Surface hardness (gmax) of infill systems determined with the Clegg Impact Tester prior to and after grooming.¹
Treatment	2005					2006
	Gmax²
	26 May	29 Jul	23 Aug	19 Sep	6 Oct	20 Apr	6 Jul	14 Aug	25 Aug	26 Sep³	25 Oct³
No Wear
Astroplay	40.3	39.2	41.6	40.6	42.1	NR	NR	NR	NR	NR	NR
Astroturf	94.6	76.5	75.6	77.7	74.8	74.0	67.3	82.3	80.4	--	--
Experimental	47.2	46.0	48.9	54.9	53.5	NR	NR	NR	NR	NR	NR
Fieldturf	60.4	56.0	56.9	59.6	63.2	60.0	57.1	62.3	55.1	--	--
Geoturf	71.4	63.9	63.0	65.2	63.8	NR	NR	NR	NR	NR	NR
Nexturf	39.6	35.4	36.7	37.3	38.8	NR	NR	NR	NR	NR	NR
Omnigrass 41	46.7	47.8	50.3	49.4	51.3	49.5	50.6	49.9	47.3	--	--
Omnigrass 51	34.9	37.8	38.4	38.5	40.3	40.1	42.7	40.0	36.9	--	--
Sofsport	58.8	55.0	58.8	57.3	57.8	56.5	62.5	58.5	58.3	--	--
Sprintturf	65.0	57.5	65.3	67.9	66.7	62.4	51.0	68.3	66.9	--	--
Wear⁴
Astroplay	48.1	46.7	50.2	49.8	49.4	NR	NR	NR	NR	NR	NR
Astroturf	80.3	89.1	87.1	84.5	83.6	78.6	78.9	93.8	90.0	90.1	88.5
Experimental	51.6	52.2	53.0	60.5	57.1	NR	NR	NR	NR	NR	NR
Fieldturf	68.0	60.2	63.6	67.9	63.5	65.1	66.9	70.6	65.5	81.5	76.7
Geoturf	75.2	70.3	71.2	71.1	69.7	NR	NR	NR	NR	NR	NR
Nexturf	40.8	40.2	40.7	41.2	42.6	NR	NR	NR	NR	NR	NR
Omnigrass 41	53.4	59.0	58.9	58.6	59.2	58.0	62.8	62.4	58.7	68.9	59.4
Omnigrass 51	40.0	44.8	45.8	47.7	47.0	49.0	53.2	52.3	45.1	57.2	48.0
Sofsport	61.1	61.8	61.7	63.0	62.9	60.8	70.2	63.5	62.8	70.8	71.3
Sprintturf	68.9	69.7	69.5	75.1	71.6	66.4	63.8	77.2	78.0	85.6	86.6
LSD (p=0.05)	7.0	1.4	1.7	1.0	1.3	3.9	2.8	8.6	3.0	9.1	10.6

¹Grooming of wear and no wear plots occurred on 5 and 9 Aug 2005.
²Surface hardness was measured using a Clegg Impact Testre equipped with a 2.25 hammer.
³Data Collected in plot ares with extreme wear (in tractor tire tracks).
⁴26 May testing performed prior to any wear in 2005. 29 Jul testing performed after wear simulating 96 games. 23 Aug testing performed after grooming. 19 Sep testing performed after wear simulating 4 games after grooming. 7 Sep testing performed after wear simulating 8 games after grooming. 13 Sep testing performed after wear simulating 8 games after grooming. 13 Sep testing performed after wear simulating 12 games after grooming. 6 Oct testing performed after wear simulating 32 games after grooming. 20 April testing performed prior to any wear in 2006. 6 Jul and 14 Aug testing performed after wear simulating 108 games. 25 Aug testing performed after grooming.
NR = Not Rated in 2006.

2005-2006 Surface Hardness (Gmax) Measured via ASTM Standard F355

Surface hardness (Gmax), Head Injury Criterion (HIC), Severity Index (SI), and pad temperature of ten synthetic turf products. 2005
Treatment	21-28 July				11-22 August
Treatment	Gmax¹	HIC²	SI³	Pad temp (°F)⁴	Gmax¹	HIC²	SI³	Pad temp (°F)
No Wear
Astroplay	78.1	185.6	214.6	79.4	80.9	200.0	231.2	74.0
Astroturf	133.0	324.5	379.9	85.8	131.4	323.7	388.6	83.1
Experimental	87.5	239.2	292.3	81.4	90.3	219.8	255.5	81.6
Fieldturf	108.2	274.5	334.2	87.5	107.0	259.4	301.9	77.7
Geoturf	108.0	268.2	312.9	88.8	111.5	285.9	334.2	87.5
Nexturf	67.9	154.0	180.1	77.4	73.3	175.7	207.7	80.9
Omingrass 41	93.9	234.3	272.6	81.9	96.4	257.3	397.6	83.5
Omnigrass 51	84.0	212.4	247.2	81.1	83.3	217.7	251.0	83.2
Sofsport	90.2	220.9	256.9	83.7	96.6	243.9	283.6	78.1
Sprintturf	108.5	248.5	293.5	82.4	115.2	282.2	330.9	76.7
Wear⁵
Astroplay	88.1	219.0	260.4	81.8	85.3	218.6	250.8	73.4
Astroturf	138.3	394.2	250.3	88.1	125.7	290.6	349.4	82.5
Experimental	113.6	313.9	393.8	80.3	98.1	246.3	286.2	81.5
Fieldturf	112.0	280.5	326.6	89.8	112.4	276.1	321.6	77.4
Geoturf	113.3	289.6	338.1	87.3	112.6	290.5	338.4	88.9
Nexturf	71.2	165.1	193.9	77.4	78.5	195.3	231.2	81.7
Omingrass 41	109.6	298.2	347.3	82.1	106.1	294.4	340.6	84.6
Omnigrass 51	91.6	250.1	293.0	81.2	96.3	273.0	315.0	83.2
Sofsport	97.4	249.9	290.4	83.5	97.4	252.3	292.8	77.5
Sprintturf	129.1	308.6	308.6	83.4	127.5	323.4	380.6	77.6
LSD (p=0.05)	14.3	88.8	130.5	7.6	11.3	52.4	61.0	9.3

¹Surface hardness was measured according to ASTM standard F355
²HIC = Head Injury Criterion
³SI = Severity Index
⁴Pad temperature was measured 0.5 inch below the pile backing
⁵F355 testing performed after wear simulating 96 games. Grooming of plots occured on 5 and 9 Aug 2005.

Surface hardness (Gmax) of six synthetic turf products determined by ASTM standard F355 prior to and after grooming. 2006
Treatment	Gmax¹
Treatment	11 Jul	18 Aug²	9 Sep	25 Sep²
No Wear
Astroturf	127.6	-	126.7	-
Fieldturf	100.5	-	113.7	-
Omnigrass 41	90.9	-	93.7	-
Omnigrass 51	79.8	-	108.1	-
Sofsport	92.9	-	99.6	-
Sprintturf	114.6	-	132.7
Wear³
Astroturf	130.3	145.0	125.7	147.1
Fieldturf	110.4	123.0	112.4	127.9
Omnigrass 41	103.8	115.8	106.1	120.8
Omnigrass 51	91.2	101.7	96.3	107.5
Sofsport	98.4	107.8	97.4	108.7
Sprintturf	128.7	135.8	127.5	139.8
LSD	3.5	16.3	11.3	13.3

¹Surface hardness measured according to ASTM standard F355
²Data collected in plot areas with extreme wear (in tractor tire tracks).
³F355 testing performed after wear simulating 108 games. Grooming of plots occured on 223-24 Aug 2006.

Agenda

Authors