Bilateral strength differences are frequently discussed as a risk factor for noncontact injuries. Research on this topic, however, is inconclusive. Therefore, the purpose of this study was to investigate the concordance of isokinetic bilateral strength differences in single-joint and multi-joint movements of the lower limb. Forty-nine track and field athletes performed multi-joint leg extensions and single-joint knee and hip extensions at two different velocities. Directed bilateral differences were calculated for all measurements. Concordance correlations were calculated to investigate magnitude and direction of the differences. Additionally, multiple linear regressions for the multi-joint movements as well as an explorative factor analysis were performed. A neuronal net was constructed to investigate whether the bilateral difference in the fast multi-joint leg extension could be predicted from the single-joint measurements. The results indicate poor to fair concordance and the factor analysis identified two independent factors: factor 1 represents bilateral differences in multi-joint and knee extensions, while factor 2 represents differences in hip extensions. The neuronal net was not able to predict the bilateral differences in multi-joint leg extensions with sufficient accuracy. Neither magnitude nor orientation of the observed strength disparities exhibit a discernible pattern across the evaluated parameters. The interchangeable utilization of bilateral strength differences from different testing conditions must be precluded. Consequently, when evaluating interlimb symmetry, it is imperative to conduct a diverse array of tests.
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