Stride Length Impacts on Sagittal Knee Biomechanics in Flat Ground Baseball Pitching

Abstract

Coordinated lower extremity biomechanics are altered in response to changes in stride length, influencing the kinetic chain that potentially induces compensatory throwing mechanics throughout the baseball pitching cycle. The respective sagittal knee dynamic profiles, for both the stride (lead) and drive (trail) leg, were analyzed during flat ground baseball pitching to determine whether the stride length variation elicits compensatory drive and stride leg knee joint kinematics, kinetics, and joint powers. Using a randomized cross-over design, a cohort of 19 healthy skilled competitive pitchers from collegiate and high school travel programs from across Western New York were assigned to throw 2 simulated 80 pitch games at ±25% of their desired stride length. An integrated motion capture system with two force plates and a radar gun tracked each throw. Pairwise comparisons at hallmark events and phases identified significantly different sagittal knee dynamics for both the drive and stride leg between the stride length conditions. During the acceleration phase, the drive knee moments between the stride length conditions demonstrated differences in power generation and absorption. Longer strides allowed for greater knee propulsion dynamics, exemplified by eccentric drive knee extensor moments with a concomitant power absorption that slowed the rate of drive knee flexion (p ≤ 0.001). Conversely, shorter strides generated power through concentric knee flexor moments that increased the rate of drive knee flexion (p ≤ 0.001). Stride knee extensor moments and power generation during the acceleration phase were also significantly higher with shorter strides (p ≤ 0.05). Adapted knee joint dynamics may offer insights into stride length optimization, training, and injury prevention strategies.