Changes in Biomechanical Risk Factors for Injury Across Normalized Running Speeds in Healthy Collegiate Cross-Country Runners.

Cross-country runners' risk for injury is high in-season potentially due to changes in biomechanics during prescribed fast running speeds and competitions. The purpose of this study was to determine if biomechanics associated with overuse knee and lower leg injury during running change similarly across speeds between female and male collegiate cross-country runners. Sixteen collegiate cross-country runners (8 females) participated. A self-selected running speed was entered into regression equations to determine treadmill speeds for the conditions: recovery (∼9% slower), threshold (∼25% faster), interval (∼36% faster), and repetition (∼50% faster). Three-dimensional lower-extremity biomechanics were collected during running. Dependent variables were analyzed via mixed-model analysis of variance and pairwise post hoc tests. Both peak rearfoot angle increased (P = .005, Cohen's f = 0.84) and rearfoot excursion increased (P = .002, Cohen's f = 0.88) with the conditions' treadmill speed. Peak knee adduction angle was greater in females compared with males (P = .032, Cohen's f = 0.67) during: recovery, easy, threshold, and interval conditions. Increases in running speed affected joint kinematics and kinetics similarly between groups. Generally, similar running biomechanics observed between females and males may indicate that faster training speeds could accentuate the contribution of rearfoot eversion to lower leg overuse injury.