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Abstract

Barefoot running alters foot strike mechanics and may change lower-extremity muscle demands compared to shod running, particularly at different speeds. PURPOSE: The purpose of this study was to examine the effects of footwear (barefoot vs. shod) and running speed (preferred vs. +20%) on normalized electromyographic (EMG) amplitude of the medial gastrocnemius (MG) and tibialis anterior (TA) in recreational runners. METHODS: Five healthy recreational runners completed treadmill running trials at preferred speed and +20% preferred speed in barefoot and shod conditions. Bilateral surface EMG was recorded from MG and TA (1500 Hz). Signals were bandpass filtered (20–450 Hz), rectified, and low-pass filtered (6 Hz) to obtain linear envelopes. MVIC trials were performed for normalization. Gait cycles were identified from envelope peaks. Mean RMS amplitude per cycle was calculated and expressed as %MVIC. A 2×2 (footwear × speed) mixed ANOVA was used to compare mean normalized EMG for MG and TA (α = 0.05), with Tukey HSD post-hoc tests for pairwise comparisons. RESULTS: For MG, normalized EMG showed a significant main effect of speed (p = 0.033) with higher activation at faster speed (bare fast: 134.4 ± 67.5 %MVIC; shod fast: 125.7 ± 72.4 %MVIC) compared to preferred speed (bare preferred: 156.3 ± 90.7 %MVIC; shod preferred: 139.3 ± 78.3 %MVIC). Pairwise comparisons revealed significant differences between barefoot preferred and both fast conditions (p < 0.001), but no significant footwear main effect or interaction. For TA, there was a significant main effect of footwear (p < 0.001) with higher activation in shod conditions, a main effect of speed (p = 0.017), and a significant interaction (p = 0.025). Pairwise comparisons showed significant differences between shod fast and all other conditions (p < 0.001). CONCLUSION: Faster running speed increased MG activation across footwear conditions, with the largest relative increase in barefoot running. TA activation was consistently higher in shod conditions and showed speed-related differences modulated by footwear. These findings suggest barefoot running may enhance plantarflexor recruitment at higher speeds, while shod running increases dorsiflexor demand, with implications for training adaptations and injury risk in recreational runners.

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