Relationships between asymmetries in functional movements and the star excursion balance test.

Lower-extremity functional asymmetries (LEFAs) have been shown to be related to performance and injury risk. However, consistency of expression between tasks is not well understood. The goal of this investigation was to examine relationships in vertical ground reaction force LEFA during standing, bodyweight squats, countermovement jumps (CMJs), and single-leg drop landings along with those produced in the Star Excursion Balance Test (SEBT). Twenty (9 men, 11 women) healthy, recreationally active young adults (mean ± SD age: 21.9 ± 2.6 years; height: 171 ± 8.8 cm; mass: 67.2 ± 1.9 kg) performed all tests in a single visit. Correlations of asymmetries between tasks as a whole group and in subsets with larger levels of asymmetries in each task were examined. Many significant correlations (p < 0.05) were found in the asymmetries between the functional tasks, between the reach directions of the SEBT, and between the functional tasks and the SEBT, though they were of low to moderate strength (|r| < 0.8) in the whole group. Except for standing, correlations typically improved in the subset analyses. Most noteworthy was the CMJ subset, which demonstrated strong relationships (|r| > 0.8) with asymmetries in the squat and with the SEBT. Correlations between reach directions in the SEBT improved in the subset comparisons but would not be considered strong. The results suggest that asymmetries are more likely to be expressed in multiple tasks as the bilateral difference increases, that intensity of effort plays a key role in the expression of asymmetries during bilateral tasks, tasks most relevant to the sport should be used when assessing athletes, and though not replacing functional tasks, the SEBT may serve an important role in the diagnosis of LEFA.