Differences in Lower Extremity Kinematics Between Collegiate and Youth Softball Pitchers

BACKGROUND: Softball pitching is a whole-body motion that utilizes the kinetic chain to transfer the large amounts of force generated by the lower extremity to the ball. Although the lower extremity is responsible for generating most of the force in softball pitching, limited research has investigated how lower extremity kinematics vary with age. PURPOSE/HYPOTHESIS: The purpose of this study was to compare lower extremity kinematics between collegiate and youth softball pitchers. It was hypothesized that there would be significant lower extremity kinematic differences between age groups. STUDY DESIGN: Descriptive laboratory study. METHODS: Overall, 83 softball pitchers participated in the study: 40 youth and 43 collegiate players. Kinematic data were collected using an electromagnetic motion capture system. All participants threw 3 fastballs to a catcher for a strike at regulation distance. Owing to nonnormally distributed data, Mann-Whitney U tests were used to determine group differences at 5 events during the pitching motion. The alpha level was set a priori at .006. RESULTS: Collegiate pitchers had significantly higher drive-knee extension angular velocity at the 3-o’clock position than youth pitchers (182.30 ± 145.44 vs –34.66 ± 219.66 rad/s; P < .001). Collegiate pitchers also had greater peak drive-knee flexion angle than youth pitchers at the top of the arm circle (37.98° ± 18.09° vs 25.38° ± 17.58°; P = .004), while youth pitchers had a significantly more anteriorly shifted center of mass than collegiate pitchers at the top of the arm circle (49.93% ± 5.09% vs 46.47% ± 6.44%; P = .003). CONCLUSION: The authors found increased drive-knee flexion angle and angular extension velocity in collegiate compared with youth pitchers, although it is unknown if these differences were due to lack of experience or strength. Athletes should work on improving drive-leg mechanics to develop optimal push-off performance. CLINICAL RELEVANCE: This information can be applied to develop strength and conditioning programs for softball pitchers. Player performance may be improved through performing exercises to strengthen knee and hip extension musculature and learning to eccentrically load the drive leg to activate the stretch shortening cycle.