Penn State Traction Study Reveals Important Data on Artificial and Natural Sports Surfaces

University Park, PA (September 24, 2013) – A recent study by Penn State University’s Center for Sports Surface Research, entitled ‘Comparison of Rotational Traction of Athletic Footwear on Varying Playing Surfaces’, has shed new light on what affects rotational traction on artificial and natural sports surfaces.

The surfaces tested in the recent Penn State study were Kentucky Bluegrass (natural), FieldTurf Revolution (artificial), AstroTurf GameDay Grass 3D (artificial), and Sportexe Omnigrass 51 (artificial). Each surface was tested in combination with 8 different shoe types and each shoe-surface combination was tested using three athlete weights.

The results show that rotational traction values on all synthetic turf surfaces were either the same or only slightly different from Kentucky Bluegrass. The FieldTurf Revolution system produced the same level of traction as Kentucky Bluegrass, while the AstroTurf GameDay Grass 3D surface resulted in traction that was the furthest away from the Kentucky Bluegrass value.

In the Penn State study, traction was measured by rotating the shoe in a forefoot stance with the weight distributed onto the forefoot as required by the American Society of Testing and Materials (ASTM) for most sports including football and soccer (ASTM F2333-04). The Pennfoot apparatus used to conduct the testing closely compares to the ASTM method for measuring traction.

A 2009 study by Villwock et al. titled ‘Football Playing Surface and Shoe Design Affect Rotational Traction’ and dubbed the “Michigan State Study”, reported larger differences between synthetic and natural turf than those observed in this study. One reason for this difference may be the manner in which traction was tested. While a testing method simulating a theoretical “worst-case” scenario such as used by the group of Michigan State University researchers is sometimes useful, if unrealistic, the results may not be applicable to scenarios experienced by athletes. Villwock et al. (2009) measured traction by rotating each shoe 90 degrees in a flat-footed stance with the weight located near the rear of the foot – a scenario that is difficult to imagine occurring during play, and if it were to occur, injury would likely result regardless of the type of playing surface. In fact, using the 75 Nm upper limit presumed by Hirsch and Lewis (1965) and referenced by Villwock et al. (2009), nearly all traction values reported by Villwock et al. (2009), including those on Kentucky bluegrass, exceeded this proposed safety limit. In the Penn State study, traction was measured by rotating the shoe in a forefoot stance with the weight distributed onto the forefoot as required by ASTM. This testing method likely represents a more realistic scenario than the method used by the Michigan State researchers.

“In the development of our mechanical test equipment our researchers have strived to mimic athlete movement and when testing try to replicate actual playing surface conditions”, said Dr. Andrew S. McNitt, Associate Professor of Soil Science, Pennsylvania State University. “The key to this study is that the cleat/shoe is positioned on the surface in a forefoot only stance in an attempt to gain realistic rotational traction data. The results we’ve reported clearly show that the type of shoe worn on these surfaces is the one variable that affects traction the most. I believe these results are consistent with many existing studies and will be borne-out in future studies.”

The differences in rotational traction among shoe types in the Penn State study was nearly four times larger than differences measured among playing surfaces. This data suggests that shoe selection has a greater influence on rotational traction and potentially lower extremity injury risk than any other variable tested.

The Penn State study has been submitted for publication and is currently under peer review. A summary of the study can be downloaded at FieldTurf.com

Update

The college's Center for Sports Surface Research has released the results of an extensive traction study that tested 30 types of athletic shoes on two natural turf surfaces -- Kentucky bluegrass and bermudagrass -- and one synthetic turf surface, FieldTurf Revolution. These are three of the most common athletic-field playing surfaces. A first-of-its-kind, online database generated from the research provides test results for many popular shoe models currently on the market from manufacturers such as Nike, Adidas and Under Armour. This information can be important to consider when selecting athletic footwear, according to Thomas Serensits, manager of the Center for Sports Surface Research. Because traction data have not been directly correlated with injury risk, researchers have not established "safe" and "unsafe" traction thresholds. But the database provides consumers with scientific data, allowing shoe comparisons specific to the type of playing surface, Serensits noted.

The traction database can be found here.

About the Penn State Center for Sports Surface Research

Penn State’s Center for Sports Surface Research is an intercollege program managed within the College of Agricultural Sciences’ Department of Plant Science. The center is dedicated to the improvement of all sports surfaces. Through cooperative scientific inquiry, the center strives to improve safety and performance on all sports surfaces.