The Effect of Field Conditions and Shoe Type on Lower Extremity Injuries in American Football ~ Jingzhen (Ginger) Yang, PhD, MPH

American football has the highest rate of lower extremity injuries in comparison to all other team sports [1,2]. Lower extremity injuries in football are often the result of complex intrinsic risk factors, such as position, age, joint flexibility, and muscle tightness, as well as extrinsic risk factors, such as field conditions, shoe-surface interaction, and equipment [3]. However, published epidemiological studies that examine these factors together are scarce and the few studies on surface type alone have yielded conflicting evidence.

Photo by GoIowaState. Used with permission. All rights reserved. Source: flickr

Photo by GoIowaState. Used with permission. All rights reserved. Source: flickr

Our study recently published in the BJSM analyzed data collected from 188 Division I players. All were from a single university football team in the United States, and played during three consecutive seasons (2007-2010).  The study compared lower extremity injury rates among collegiate football players by playing surface and shoe type during football games and practices.

The findings showed that when surface conditions were abnormal (e.g., the temperature was over 82°F, the humidity was over 50 percent, or visible water spots were seen on the surface), the lower extremity injury rate was more than 2.5 times as high. This was particularly evident during practice sessions.

Another rather unanticipated finding of this study, risk for lower extremity injury, was 3.34 times higher on artificial turf as compared to natural grass during games. This trend was not observed during practice sessions. Findings also indicated that shoe type, including number of cleats and height of shoe top, was not associated with lower extremity injury rates.

This represents the third study in the last two years from the United States reporting significantly greater injury risk on artificial turf [4,5]. These results are supported by the previous studies, which found the excessive rotational shoe-surface traction can cause foot fixation, increasing the risk of lower extremity injuries, such as ACL injury [6-9].

With constant directional and speed changes such as cutting, pivoting, starts and stops, and backpedaling associated with football, artificial turfs could likely play a role in non-contact, lower-extremity injuries including medial/lateral collateral tears, anterior/posterior cruciate tears, and damage to the meniscus.

The results from this study may provide an important practical insight for athletic programs when selecting surfaces to best protects their players, and for athletes to select shoes for varying weather conditions in order to avoid injury.

Jingzhen (Ginger) Yang is an Associate Professor in the College of Public Health at Kent State University. Dr. Yang’s research is focused on injury and violence prevention and control among youth and adolescents, specifically sports injury prevention and control. She was a director of Training Core and Team Leader of  one of 11 CDC funded Injury Prevention Research Centers of excellence. In 2010, she was appointed to serve on the Major League Baseball Injury Research Committee.


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