Interlimb asymmetries: the need for an individual approach to data analysis

It has been shown that the magnitude of inter-limb asymmetries varies depending on the test selected; however, literature relating to whether asymmetries always favour the same limb is scarce. The aim of the present study was to determine whether inter-limb asymmetries always favoured the same side for common metrics across unilateral strength and jumping-based tests. Twenty-eight recreational sport athletes performed unilateral isometric squats, single leg countermovement jumps (SLCMJ) and single leg broad jumps (SLBJ) with asymmetries in peak force compared across all tests, and eccentric and concentric impulse asymmetries compared between jumps. Mean asymmetries for all tests were low (≤ -5.3%) and all inter-limb differences for jump tests favoured the left limb, whilst asymmetries during the isometric squat favoured the right limb. Despite the low mean asymmetry values, individual data highlighted substantially greater differences. Levels of agreement for asymmetries were computed via the Kappa coefficient and ranged from slight to substantial (< 0.01 – 0.79), although concentric impulse asymmetries for jump tests was the only comparison to result in substantial levels of agreement. With asymmetries rarely being present on the same side across tests, these results show that a more individual approach to reporting asymmetries is required, which should help practitioners when designing targeted training interventions for their reduction