Abstract
This study analyzed relationships between bilateral concentric(60°/s, 180°/s, 240°/s) and eccentric (30°/s) knee extensor and flexor strength differences, and linear (40-meter sprint), and change-of-direction (T-test) speed in 16 male team sport athletes. It was hypothesized that lower between-leg strength differences would be associated with faster speeds. Subjects were divided into faster and slower groups based on total time; a one-way analysis of variance (p ⩽ 0.05) determined bilateral torque and work differences that distinguished the groups. All data was combined to correlate (p⩽ 0.05) torque and work differences with sprint times. The faster group exhibited greater differences in concentric knee extensor torque at 240°/s (faster=11.74 ± 8.65%; slower= 4.13 ± 4.34%), and smaller differences in eccentric knee flexor torque(faster=5.64 ± 4.10%; slower=12.41 ± 7.55%) and work(faster=6.36 ± 6.65%; slower=15.55 ± 6.05%). Negative correlations were found between concentric 180°/s and 240°/s knee extensor torque differences and sprint times; however, speed was not negatively affected. Positive correlations existed between eccentric knee flexor work differences and sprint times. Eccentric strength differences negatively impacted multi-directional speed, as balanced eccentric strength is necessary for effective sprinting, deceleration, and changing direction.