Measuring Interlimb Asymmetry for Strength and Power: A Brief Review of Assessment Methods, Data Analysis, Current Evidence, and Practical Recommendations

Abstract

Bishop, C, de Keijzer, KL, Turner, AN, and Beato, M. Measuring interlimb asymmetry for strength and power: A brief review of assessment methods, data analysis, current evidence, and practical recommendations. J Strength Cond Res 37(3): 745–750, 2023—The aim of this brief narrative review is to summarize the present evidence, provide recommendations for data analysis, and provide appropriate training methods to reduce strength and power asymmetries within athlete populations. Present evidence shows that a strong interest in the assessment of asymmetry exists. Despite the perceived associated relationship between asymmetry and injury and performance, a clear link is still missing. Practitioners need to be aware of this when they decide to assess asymmetries and later design training interventions. Several bilateral and unilateral tests could be used to assess asymmetries, such as isokinetic dynamometry, the isometric mid-thigh pull, squat, and Nordic hamstring exercise. Based on the current evidence, future investigations require further standardization of methodology and analysis to optimize interpretation (e.g., within session and between session), adoption, and implementation of interlimb asymmetry testing and appropriate interventions. In this review, 3 training interventions have been proposed to reduce existing lower limb asymmetries in sport populations: traditional resistance training, flywheel resistance training, and combined training interventions, with some evidence suggesting that such interventions can reduce lower limb asymmetries. Nonetheless, the number and quality of articles currently available are too limited to draw firm conclusions; therefore, further research is needed to verify whether training interventions can achieve these aims. To develop an understanding and application of interventions addressing interlimb asymmetries within the sport, greater methodological rigor should be applied toward study design, data analysis, and interpretation of future investigations and when appraising the current literature.

The Isokinetic Method in Female Uninjured Female Soccer Players: A Survey of Applications and Common Mismatches

“…The protocols were sometimes poor described (e.g no rest time between series were reported, and no previous training schedule of athletes or menstrual cycle phase at the time of test were reported). These observations are in agreement with a recent study [48], which critically evidenced that, considering the available evidence, it need more investigations and an improving in standardization of methodology and analysis to optimize interpretation (e.g., within session and between session), adoption, and implementation of interlimb asymmetry testing, and subsequent appropriate interventions [48]. The same study also calls for a greater methodological rigor, to be applied in study design, data analysis, and interpretation of isokinetic (and other tests for asymmetry) and also when reviewing the current literature.…”

A comparison of neuromechanical adjustments to traditional and eccentric load reduction weighted jump squats

“…This is not in keeping with literature suggesting that even uninjured individuals present inherent low‐to‐moderate mechanical asymmetries (Afonso et al., 2022). With assessments of bilateral asymmetries being highly metric‐, task‐, and individual‐specific (Bishop et al., 2023), verifying that left and right legs actually behave similarly during all WJS phases should be an avenue for future research. Such studies should not only recruit healthy athletes but also those presenting significant force deficits on one side of the body.…”

Attentional Focus Effects on Lower-Limb Muscular Strength in Athletes: A Systematic Review

“…Moreover, McBride et al (63) found no significant correlation between peak force and JH in SJ and CMJ, with various loads and depths. Finally, peak force is proved to be a useful metric to measure interlimb asymmetry in injured athletes (12,13), rather than assessing muscular strength performance in unweighted ballistic tasks. In conclusion, taking inspiration from Bishop et al (14) and Harry et al (45) when assessing the effects of attentional focus for ballistic tasks, we recommend that consideration be given to the kinetic outcomes, such as displacement, duration of braking or propulsive phase, and mean net force or net impulse, and the performance outcomes, such as JH or jump momentum, whereas for nonballistic tasks, displacement and net impulse should be considered.…”