Using the single leg squat as an assessment of stride leg knee mechanics in adolescent baseball pitchers

Lack of control of the lower extremity or trunk during single leg tasks is often associated with pathomechanic adaptations during the pitching motion which may increase the risk of pain and injury to the upper extremity. The objectives of the study were to determine the amount of variability in stride knee mechanics accounted for by compensations during a common movement assessment, the single leg squat (SLS) and to establish the usefulness of SLS as a screening tool for at-risk athletes.

Cross-sectional design.

Sixty-one adolescent baseball pitchers performed a SLS on each leg. Participants performed three fastball pitches to a catcher at a regulation distance. Kinematic data were collected at 100Hz using an electromagnetic tracking device.

MANOVAs with follow-up one-way ANOVAs were used to examine the amount of variance in pitching knee mechanics explained by SLS compensations. At stride foot contact, there was a significant effect of SLS valgus angle on knee valgus angle (F_1,51=23.16, p<0.001, η_p²=0.31) and valgus moment (F_1,51=8.28, p=0.006, η_p²=0.14). At ball release (BR), there was a significant effect of SLS valgus angle on flexion angle (F_1,51=9.37, p=0.004, η_p²=0.16) and valgus angle (F_1,51 = 26.93, p<0.001, η_p²=0.35). Examination of the average values occurring between SFC and BR, revealed a significant effect of SLS valgus angle on knee valgus angle (F_1,51=30.91, p<0.001, η_p²=0.38).

SLS compensations are potentially a useful screening tool for stride knee mechanics in adolescent baseball pitchers.