Lower-Body Muscle Volumes Can Explain Half of the Variance in Sprint Speed Between Collegiate American Football Players.

Sprinting speed is critical for success across many sports. Lower-body muscle size is important, but it is difficult to determine which muscles have the greatest influence on speed, and it is unclear how much variance in speed between athletes can be explained by variance in muscle size alone. The purpose of this study was to determine how much variance in on-field sprinting speed can be explained by individual and combined lower-body muscle volumes. Sprint speed was measured in sixty-six collegiate football players using inertial measurement units, and muscle volumes were determined using magnetic resonance imaging. Coefficients of determination were calculated between speed and individual muscle volumes, summed volumes, and optimized linear combinations of volumes. Psoas major volume explained the most variance in sprint speed (50%), followed by gluteus medius (45%) and gluteus maximus (37%). The top sum of three muscle volumes (psoas major, gluteus medius, piriformis) explained an additional 7% of the variance in speed compared with psoas major alone. Similarly, the top optimized linear combination of muscle volumes (psoas major, gluteus medius, piriformis) explained 9% more variance than psoas major alone. These results indicate that psoas major volume is most predictive of sprinting speed, and that accounting for multiple muscle volumes may have limited additional benefit.