Comparing unilateral and bilateral assessments of adductor isometric strength symmetries

This study aimed to evaluate the relationship between unilateral and bilateral assessments of adductor strength, as well as inter-leg adductor strength symmetry, and to assess the intra-session reliability of the results for each testing condition. Nineteen physical education students performed three adductor strength test protocols in a supine position with hips and knees extended: (a) unilateral, (b) bilateral, and (c) bilateral following a unilateral adduction fatigue protocol. Bilateral and unilateral strength measures indicated good-excellent reliability across tests (intraclass correlation coefficient>0.88 and coefficient of variation<8%), while unilateral symmetry showed poor reliability (intraclass correlation coefficient=0.47 and coefficient of variation=13%). Bilateral testing produced statistically significantly higher strength values (p<0.05) than unilateral testing; however, no significant differences were observed between unilateral and bilateral tests under fatigued conditions, regardless of leg preference (preferred or non-preferred). Despite an average strength decrease of 35% after the unilateral fatiguing protocol, bilateral test symmetry results did not change (101% vs. 106%). A very strong correlation was observed between bilateral and unilateral adductor strength results (r=0.81-0.86); yet, no correlation was significant for symmetry results (r<0.35, p>0.05). Due to the limited sensitivity of the bilateral adduction test for detecting changes in symmetry values, we recommend the unilateral testing protocol for practical use when assessing inter-leg adductor muscle strength asymmetries.