Differential T2* changes in tibialis anterior and soleus: Influence of exercise type and perceived exertion

Understanding muscle response to exercise is critical for optimizing training strategies. This study investigated the effects of dorsiflexion and plantar flexion exercises on T2* values in the tibialis anterior (TA) and soleus (SOL) muscles and explored their relationship with muscle cross-sectional area (MCA), strength, and perceived exertion. Forty participants were divided into two exercise protocols: 30 performed dorsiflexion, 16 performed plantar flexion, and 6 completed both. T2* values were measured pre-and post-exercise using a 1.5 T MRI scanner. MCA and muscle strength were assessed via MRI and a dynamometer, while perceived exertion was measured using the Borg scale. Results showed that TA T2* values significantly increased after dorsiflexion (9.04 ± 4.21 ms), peaking 600 s post-exercise, whereas SOL T2* changes during plantar flexion were minimal (1.29 ± 1.05 ms). A significant correlation (r = 0.41, p = 0.026) was observed between T2* changes and Borg scale scores during dorsiflexion, but not with muscle strength (r = 0.08) or MCA (r = 0.35). No significant correlations were found for the SOL during plantar flexion. General linear model analysis showed a significant main effect of dorsiflexion on T2* values (p < 0.0001) and perceived exertion within the dorsiflexion protocol (p = 0.044). These findings suggest that dorsiflexion induces greater metabolic disturbances in the TA compared to plantar flexion. The results emphasize the importance of exercise-specific approaches for assessing muscle function and highlight the role of perceived exertion in evaluating muscle response.