Effects of a 2-hour cheerleading practice on dynamic postural stability, knee laxity, and hamstring extensibility

Study Design: One group; pretest, posttest design. Objective: To assess the effect of a 2-hour cheerleading practice on the an terior knee laxity, hamstring extensibility, and dynamic postural stability (preferred stance leg during vision-denied unilateral stance) of 17 nonimp aired members of a college cheerleading team (8 females, 9 males; 18-25 yea rs old). Background: Anterior knee laxity and hamstring extensibility increase follo wing exercise. The relationship between exercise induced anterior knee laxi ty, hamstring extensibility, and dynamic postural stability, however, has n ot been examined. Methods and Measures: Pre- and postpractice measurements were compared usin g paired t tests and Bonferroni's correction for multiple comparisons. A 3 x 2 analysis of variance (force level applied to the arthrometer by conditi on) and Tukey honest significant difference post hoc test were used to eval uate specific arthrometer force level by condition effects (P < .05). Results: Mean laxity at 133 N and hamstring extensibility increased (mean /- SD) 1.5 +/- 1 mm and 3 +/- 4 degrees, respectively, following practice. Mean medial-lateral stabiliometer platform angulation (frontal plane positi on) moved medially following practice (2.9 +/- 3 degrees) and produced a we ak correlation with increased knee laxity (r = 0.58). Hamstring extensibili ty did not significantly relate to stabiliometry or knee laxity variables. Conclusions: The relationship between the medially directed platform angula tion and the increase in anterior knee laxity following cheerleading practi ce suggests a relationship between subtalar joint position and anterior cru ciate ligament strain.