Foot-ground Contact Forces in Elite American Football Players: Do Heavier Players Run Softer?

Nova Southeastern University, Davie, Florida, USA

Objective. The objective of the study was to determine if body mass was related to vertical foot-ground contact forces in American football players. Background. American football players seeking to be drafted by the National Football League (NFL) showcase their running abilities in the 40 yard dash. Top performers are typically lighter, but heavier players must also demonstrate speed. High foot-ground contact vertical forces are associated with increased speed. Methods. Twenty adult male American football players from across the United States training for the NFL draft (age, 22.1+/-2.1 yrs; height, 1.83+/-0.10 m; mass, 98.9+/-16.1 kg) participated in this study. Subjects ran for 5 sec bout between 6.0-6.5 m/s on an instrumented treadmill. Data were smoothed with a low pass Butterworth filter with a cut-off frequency of 5 Hz. Body mass was measured in kilograms using an InBody device. We examined the relationship between average vertical foot-ground contact forces, or average vertical ground reaction forces (vGRF) and body mass. Pearson’s correlation coefficients were calculated to determine associations between body mass and vGRF for both the right and left sides, p<.05. Results. Mean vGRFs for the foot-ground contact were 1.65+/-0.15 body weights (BW) for the right side and 1.66+/-0.20 for the left. Body mass was moderately and negatively associated with vGRF for both the right (r=-0.549, p=0.018) and left (r=-0.530, p=0.024). Conclusion. American football players’ running performance is affected by their mass with heavier players running softer. This may be an injury prevention strategy. Grants. This study did not receive funding.