[Delayed activation of ankle muscles in young adults with excess adiposity]

Introduction: obesity is linked to functional impairments that affect mobility and motor control. Excess body fat may compromise neuromuscular activation; however, its relationship with ankle muscle reaction time in young adults has been scarcely studied. Objectives: to analyze differences in ankle muscle reaction time among young adults according to their body fat percentage (normal, elevated, and very elevated). Methods: a cross-sectional observational study was conducted with 48 young adults. Participants were classified based on body fat percentage. Reaction times of the tibialis anterior, peroneus longus, and medial gastrocnemius were measured using surface electromyography during a sudden ankle inversion test. ANOVA and linear regression were applied to analyze group differences and associations. Results: significant differences were found between groups for the tibialis anterior (p < 0.001), peroneus longus (p = 0.010), and medial gastrocnemius (p < 0.001). The group with very high body fat showed delayed activation in all muscles. Regression analysis revealed that a very high fat percentage was associated with longer reaction times in the tibialis anterior (β = 15.85 ms; p = 0.006), peroneus longus (β = 12.85 ms; p = 0.008), and medial gastrocnemius (β = 17.84 ms; p = 0.007), compared to the normal fat group. Conclusions: a higher body fat percentage is associated with longer muscle reaction times in ankle muscles. This finding highlights the importance of considering body fat percentage as a key factor in assessing and designing neuromuscular interventions for young adults.