Associations of lean mass and phase angle lower inter-limb asymmetry magnitude with training volume and running performance

Introduction: Inter-limb asymmetry has recently gained increasing attention being considered as potentially detrimental to athletic performance. However, research exploring the relationship between morphological asymmetry and running performance is very scarce. This study aimed to investigate (1) the association between training volume, and lean mass (LM) and phase angle (PhA) lower inter-limb asymmetry magnitude; and (2) the association between LM and PhA lower inter-limb asymmetry magnitude, and running performance.
Methods: This cross-sectional study included 59 adults (29 males, 30 females; aged 20–51 years). Training volume (i.e., hours spent running per week) was self-reported via an online questionnaire. Bioelectrical impedance analysis (BIA, Inbody S10) measured segmental LM and PhA. Lower inter-limb asymmetry magnitude was calculated using the percentage difference method: ((highest value – lowest value) / highest value) × 100. Running performance was assessed using the Cooper test (i.e., distance covered within 12 minutes). Adjusting for participants’ age and sex, multiple linear regression analyses examined (1) the predictive value of training volume for lower inter-limb LM and PhA asymmetry magnitude; and (2) the predictive value of lower inter-limb LM and PhA asymmetry magnitude for running performance.
Results: Our results demonstrated no significant associations of training volume with the magnitude of lower inter-limb asymmetry in LM (p = 0.055, β = -0.251) and PhA (p = 0.204, β = -0.169). Additionally, no significant associations were observed of the magnitude of lower inter-limb asymmetry in LM (p = 0.625, β = -0.060) and PhA (p = 0.516, β = -0.079) with running performance.
Conclusion: These findings suggest that distance runners’ training volume is not associated with the magnitude of LM and PhA asymmetry at the lower limb level, and that the latter does not relate to running performance. Further research on the impact of inter-limb asymmetry in terms of injury risk also seems warranted.