Unilateral isometric squat: test reliability, interlimb asymmetries, and relationships with limb dominance

The aim of this study was to determine test reliability, establish interlimb asymmetries and their associations with force production capability on the dominant (D) and nondominant (ND) limbs during the unilateral isometric squat test. Twenty-eight recreational sport athletes attended a single-test session after familiarization and performed 3 trials on each limb with 140° of hip and knee flexion, to assess peak force (PF), rate of force development (RFD), and impulse at different time intervals. Reliability, interlimb asymmetries, and Pearson's r correlations were computed thereafter. Test reliability was metric-dependent with only PF showing good levels of reliability on both limbs (coefficient of variation = 5.44–5.70; intraclass correlation coefficient = 0.93–0.94). Interlimb asymmetries ranged from 8.36 to 25.46%, with a tendency for RFD and impulse asymmetries to reduce as time intervals increased. Three significant negative relationships of a possible 49 (r = −0.43 to −0.47; p < 0.05) were found between asymmetries and performance on the D limb. However, 31 significant negative correlations (r = −0.42 to −0.71; p < 0.05) were found between asymmetries and performance on the ND limb. These findings demonstrate that practitioners may only be able to use PF as a reliable test metric during a unilateral isometric strength test. Furthermore, the negative association between asymmetries and strength performance on the ND limb may indicate that the reduction of imbalances through targeted training interventions may be warranted.