Acute Neuromuscular Responses and Interlimb Asymmetry Following 5 km and Half-Marathon Running in Recreational Runners

Acute neuromuscular responses to running may vary according to exercise duration and physiological demands. This study compared changes in vastus medialis contractile properties, quadriceps maximal voluntary isometric contraction (MVIC), and interlimb asymmetry following 5 km and half-marathon running trials. Twenty-eight male recreational runners (36.96 ± 11.35 years) completed both trials 10 days apart. Maximal radial displacement (Dm), contraction time (Tc), and contraction velocity (Vc) were assessed using tensiomyography, while quadriceps MVIC was assessed using isometric dynamometry before and after each trial. Absolute interlimb asymmetry and its direction were also analysed. The unadjusted analysis showed a greater pre-to-post increase in Dm following the half-marathon; however, the effect of the running trial on post-running Dm was not significant after adjustment for baseline Dm. Tc and MVIC decreased after both trials, whereas Vc increased, with no significant running trial × time interactions for these outcomes. TMG- and MVIC-derived absolute interlimb asymmetry remained unchanged. Acute post-running responses differed according to the neuromuscular characteristic assessed rather than consistently according to running distance. Changes in contractile properties and maximal force-generating capacity were not accompanied by a systematic increase in the magnitude of between-leg differences.