Andrew S. McNitt

Development and Evaluation of a Method to Measure Traction on Turfgrass Surfaces

Traction, as it relates to field quality, involves the athlete, studded footwear, and the turf. Traction involves two types of forces: those acting in a vertical manner that compress the turf and those that act horizontally and produce a shearing or tearing effect on the turf. The objectives of this research were to develop and evaluate an apparatus to measure the horizontal forces associated with traction, compare this apparatus with other devices routinely used to quantify traction, and examine how different turfgrass stand characteristics combine to influence traction. An apparatus, termed PENNFOOT, was developed and field tested. PENNFOOT consists of a framework that supports a leg and foot assembly that can be used to measure both rotational and linear traction using different footwear under various loading weights. When we compared PENNFOOT to other traction measuring devices, the force values we obtained from different grass species and varying cutting heights provided low correlation values. Experiments were conducted to determine the effect of turfgrass and soil conditions on traction of turf areas. Tall fescue and Kentucky bluegrass provided the highest traction values whereas perennial ryegrass and creeping red fescue provided the lowest. Higher linear traction values occurred with lower cutting heights. Although more work is needed on the turf and soil characteristics that influence traction, the PENNFOOT with its versatility seems appropriate for traction evaluation.

Surface Conditions of Highly Maintained Baseball Fields in the Northeastern United States: Part 1, Non-Turfed Basepaths

Quantitative information about the playing surface quality of highly maintained non-turfed basepaths is minimal. Playing surface quality has many components including surface hardness and pace. Hardness is the degree to which forces are attenuated upon impact with a surface. Pace is a measure of the relative velocity at which a ball travels after impacting a surface. A survey was conducted in 2005 to document the hardness and pace of non-turfed baseball field basepaths in the northeastern United States. Non-turfed basepaths measured very high in surface hardness, often exceeding maximum safety levels set by the United States Consumer Product Safety Commission. Other basepath characteristics such as soil texture, soil moisture, concentration of calcined clay conditioner, and scarification depth were documented and compared to surface hardness and pace.

Measurement of Bulk Mechanical Properties and Modeling the Load-Response of Rootzone Sands. Part 2: Effect of Moisture on Continuous Sand Mixtures

The compression and failure responses of four rootzone sand mixtures (with different types of particle shapes) were analyzed, compared, and modeled at two different moisture states (air dried and 30 cm tension). Differences in particle packing characteristics arising from particle shape and moisture were quantified. The air-dried and moist samples of the sand mixtures had initial bulk density (IBD) values ranging from 1.55 to 1.67g/cc and 1.23 to 1.48g/cc, respectively. The low IBD values observed for moist mixtures were attributed to the particle-particle agglomeration effects that take place in the presence of moisture. In addition, it was observed that the sand mixtures porosity increased with decreasing particle sphericity. During compression testing, moist samples underwent a greater volumetric deformation compared to the air-dried samples for the same pressure levels, e.g., at 69kPa, the volumetric strain of moist round sand mixtures was 8% higher than that of the air-dried round sand mixtures. Therefore, moisture acted as lubricant during volumetric compression of sand mixtures. Also, the bulk modulus values decreased with increasing moisture content and decreasing particle sphericity. During shear testing, the moist samples underwent a larger amount of strain deformation compared to the air-dried samples for the same stress difference values. This suggests that the presence of moisture makes the sand mixtures ductile during shear testing, unlike the usual brittle response in air-dried state. Shear modulus values linearly increased with the increase in mean pressure for the air-dried samples, whereas, for moist samples, the shear modulus values increased gradually or remained practically constant. The effect of pressure, moisture, and particle shape was also quantified for two elastoplastic parameters (consolidation and swelling indices). It was generally observed that the average consolidation index values decreased with pressure but increased with moisture and particle angularity. On the other hand, average swelling index values increased with pressure, moisture, and particle angularity. Overall, it was concluded that the moisture and particle shape had a decisive influence on the compression and shear profiles of continuous rootzone sand mixtures.

Surface Conditions of Highly Maintained Baseball Fields in the Northeastern United States: Part 2, Synthetic versus Natural Turfgrass

Pace is a measure of the relative velocity at which a ball travels after impacting a playing surface. Information about the pace of balls impacting highly maintained natural and synthetic turf baseball field surfaces is minimal. A survey was conducted in 2005 to document the pace and surface hardness of baseball field playing surfaces in the northeastern United States. Nine natural turfgrass baseball fields and five synthetic turf fields were evaluated. Surface pace and surface hardness values of these highly maintained fields differed little between synthetic and natural turfgrass. Surface pace measurements on synthetic turf surfaces were slightly less variable from field to field than those measured on natural turfgrass surfaces. Much greater differences in surface pace and hardness were detected between the non-turfed basepaths, reported in Part 1 of the project, compared to either natural or synthetic turf. Within the parameters of this study, the natural turfgrass surfaces and the infilled synthetic turf surfaces evaluated differed little in surface pace or surface hardness.

Improving surface stability on natural turfgrass athletic fields

Regardless of the intensity of use, athletic fields are expected to provide a safe stable playing surface. As field use increases, wear caused by foot traffic can result in a loss of both turfgrass coverage and surface stability, increasing the risk of athlete injury. As surface stability is reduced, susceptibility to divoting is increased. The effect of synthetic soil reinforcements on the divot resistance of perennial ryegrass (Lolium perenne L.) under various simulated traffic levels was investigated. Soil-reinforcing materials improved divot resistance most under high traffic. Because the plant growth regulator trinexapac-ethyl (TE) has been shown to increase tiller density and rooting, its effect on divot resistance was evaluated on turfgrass grown on a sand root zone. TE (0.17 kg active ingredient/ha) was applied to Kentucky bluegrass (Poa pratensis L.) at 28 day intervals from either May to July or May to October. Plots were subjected to various levels of simulated traffic in the fall. Compared with the control, the application of TE from May to July resulted in the highest divot resistance. Various methods such as the inclusion of soil reinforcements and plant growth regulator applications can be used to decrease susceptibility to divoting.

An Apparatus to Evaluate the Pace of Baseball Field Playing Surfaces

During a baseball game, the ball will strike the playing surface at a variety of speeds and angles. The speed at which the ball travels after impact with the playing surface has been referred to as the pace of the surface. Wide variations in pace can reduce the safety and playability of baseball field surfaces. Pace can be quantified by measuring the coefficient of restitution. The coefficient of restitution is defined as the ratio of two velocities; the velocity of a baseball after impact with the surface divided by the velocity of the ball prior to impact. An apparatus was developed to measure the coefficient of restitution of a baseball striking various playing surfaces. The apparatus, termed Pennbounce, uses infrared screens to measure the coefficient of restitution of baseballs propelled at varying angles and velocities. Pennbounce was used to measure the pace of traditional synthetic turf (Astroturf), infilled synthetic turf (Fieldturf), natural turfgrass, and skinned infield surfaces. Baseballs were propelled at the surfaces using two velocities and impact angles. Surface pace was highest on traditional synthetic turf, skinned infield, infilled synthetic turf, and natural turfgrass areas, respectively.

Comparison of Rotational Traction of Athletic Footwear on Varying Playing Surfaces Using Different Normal Loads

As an athlete accelerates, stops, and changes direction, numerous forces are transmitted to the lower extremities. The interaction between an athlete’s shoe and the playing surface has been indicated as a factor in lower extremity injury risk. In particular, high rotational forces may result in increased injuries to the lower extremities. Rotational traction forces produced by eight different cleated shoes on Kentucky bluegrass (Poa pratensis L.), AstroTurf GameDay Grass 3D, FieldTurf Revolution, and Sportexe Omnigrass 51 under three normal loads (vertical forces) of 787, 1054, and 1321 N were measured using Pennfoot, a portable traction testing device. Of the treatments in this study, shoe type influenced rotational traction most, with differences among shoes being nearly four times as large as those among playing surfaces. Traction was either the same or within several Nm on each surface tested. Traction on the three synthetic turf surfaces ranged from 49.3 to 53.1 Nm and the traction level of Kentucky bluegrass was 52.3 Nm. Traction levels among shoes ranged from 43.8 to 58.6 Nm. The results of this study indicate that footwear selection has a larger effect on rotational traction, and potentially injury risk, than the playing surfaces evaluated in this study. Traction Testing on Natural and Synthetic Turf The interaction between an athlete’s shoe and the playing surface likely influences lower extremity injury risk. Specifically, injuries to lower extremities may result from an athlete’s foot becoming “entrapped” in the playing surface during pivoting movements (Lambson et al, 1996; Orchard et al., 2001; Torg et al., 1974). Researchers have attempted to quantify lower extremity injury risk by measuring the rotational traction forces that occur between shoes and playing surfaces (Andreasson et al., 1986; Bonstingl et al, 1975; Heidt et al., 1996; Livesay et al., 2006; McNitt et al., 2004a; Torg et al., 1996; Villwock et al., 2009a, 2009b). Rotational traction is the traction related to rotational motion about an axis normal to the surface (American Society for Testing and Materials, 2009). In the following studies, Published in Applied Turfgrass Science DOI 10.2134/ATS-2013-0073-RS

Measurement of Bulk Mechanical Properties and Modeling the Load Response of Rootzone Sands. Part 3: Effect of Organics and Moisture Content on Continuous Sand Mixtures

The interactions between organics and sand particles at different moisture contents are important in understanding the general mechanical behavior of rootzone sand mixtures. Towards this end, eight rootzone sand mixtures (4 shapes 2 2 moisture contents) used in golf green construction were tested using the cubical triaxial tester (CTT). These eight mixtures consist of sphagnum peat as the organic source and four sands of varying particle shape (round, subround, subangular, and angular). The sand-peat mixtures were tested at two moisture contents (air-dried and 30 cm tension). Of all the test samples, air-dried round sand with peat had the highest initial bulk density (IBD) value (1.49 g/cc), while moist angular sand with peat had the lowest IBD value (1.23 g/cc). These values influenced the compression behavior of samples, for example, the air-dried round sand with peat was least compressible while moist angular sand with peat was most compressible. Generally, moisture enhanced the compressibility of test specimens. At an isotropic pressure of 100 kPa, the volumetric strain value of moist round sand with peat was 47% higher than the volumetric strain value of the air-dried round sand with peat. Consequently, moisture and peat in bulk sand samples act as lubricants and assist in the compression process. In addition, bulk modulus values decreased with moisture. Due to the dominant effect of peat, there were no large differences between bulk modulus values of different particle shapes. The shear and failure responses of the above-mentioned eight compositions were also analyzed, compared, and modeled. Of all sand mixtures tested, air-dried angular sands with peat had the highest brittle-type failure stress value, 181 kPa at 34.5 kPa confining pressure, and moist subangular sand with peat had the lowest ductile-type failure stress value, 141 kPa at the same confining pressure. Shear modulus values increased with the increase of mean pressure, but in the case of sands containing both moisture and peat, shear modulus values increased gradually. Overall, peat and moisture content have a dominant effect on the compression and failure behavior of the rootzone sands. rootzone sand mixtures moisture effect particle shape effect organics effect mechanical behavior compression response shear/failure response prediction models

Effects of Surface Conditions on Baseball Playing Surface Pace

The speed at which a baseball travels after impact with a playing surface has been referred to as playing surface pace. Little information is available regarding the effects of varying construction and maintenance practices on the pace of baseball playing surfaces. Research was conducted to evaluate the effects of construction and maintenance practices on a non-turfed basepath, Kentucky bluegrass (Poa pratensis L.) turf, and six synthetic turf surfaces. Factors evaluated on the non-turfed basepath included soil compaction at installation, surface scarification, and topdressing with a soil conditioner (calcined clay). The effects of cutting height and thatch thickness were evaluated on Kentucky bluegrass, while the effects of simulated traffic and grooming were evaluated on synthetic turf. On the non-turfed basepath, increasing soil compaction yielded increases in surface pace. Calcined clay topdressing and increasing scarification depth did not affect surface pace. On Kentucky bluegrass, varying cutting height and thatch thickness levels had no effect on surface pace. On synthetic turf, increases in simulated traffic resulted in slight increases in pace. Surface pace measurements on synthetic turf were less variable than those made on natural turfgrass. The results indicate that the pace of commonly used baseball playing surfaces is not easily altered with minimally invasive maintenance procedures and should be addressed at construction or during aggressive renovations.