The Relationship Of Stride Length And Joint Stresses Among Adolescent Female Fastpitch Softball Pitchers

Abstract

PURPOSE: During the softball windmill pitch delivery, power is generated from the lower extremities and transferred up through the kinetic chain out to the throwing hand. At time of stride, the lead lower extremity incurs significant momentum breaking forces that could contribute to injury risk. Joint angle positions at the time of stride may vary based on stride length and extreme ranges of stride length may correlate with biomechanics that are associated with vulnerability to injury. This study investigates the relationship between stride length and 1) joint angles of the lead lower extremity at time of stride and 2) peak joint torques of the lead hip and throwing shoulder during the softball windmill pitch. METHODS: 17 pitchers (mean age= 15.4 ± 1.4 y) underwent 3D biomechanical analysis of 80 fastballs using a 20 motion capture camera system (Vicon Motion Systems Ltd UK) at 240 hz. A 15-segment whole-body model for each pitcher was created. Ankle, knee, hip, and pelvis angles of the lead lower extremity and peak hip and shoulder torques at time of stride were calculated within a biomechanical analysis software (Visual 3D v6, C-Motion). Analyses included 2-tailed Pearson correlations. RESULTS: Stride length correlated positively with peak shoulder external rotation torque (r= 0.245, p= 0.029), lead ankle eversion/inversion, and hip flexion/extension angle at time of stride. Stride length negatively correlated with lead knee valgus/varus, hip abduction/adduction, hip rotation, and pelvis flexion/extension angle at the time of stride (Table 1). No other correlations were observed. CONCLUSION: The most prevalent reported injuries among softball pitchers occur at the shoulder, hip, and low back. Study findings suggest that pitch instruction on lead leg joint position at time of stride as well as stride length may be important for injury prevention during fast pitch softball pitching.