Introduction. Arches of the foot play a significant role in lower limb function and impairments in the arches are correlated to increased injury risk. The aim of this study was to identify the difference in muscles activity in individuals with a flat foot as compared to those with normal foot arch using surface electromyography (sEMG) while walking on at different speeds and gradients (slope of the treadmill). Material and Methods. Sixty healthy subjects were recruited by convenience sampling method and equally divided into two groups: short arch group (n = 30) and normal arch group (n = 30) by measuring arch height. All the subjects were made to walk on a treadmill at varying speeds (2.7, 4.5, and 6.3 km/h) and gradients (0%, 3%, 6% and 9%). The sEMG activity was recorded for medial gastrocnemius (GM) muscle and peroneus longus (PL) muscle while walking on the treadmill. Results. 2 x 3 x 4 split-plot ANOVA revealed a significant group effect for GM activity (p < 0.001), whereas PL activity was not able to show a significant group effect (p = 0.109). Increasing speeds led to a significant difference in the sEMG activity of PL and GM muscles (p < 0.001) in the two groups. Increasing gradient of treadmill also showed a significant difference in the sEMG activity in the two groups for PL and GM muscle (p < 0.05). Conclusions. The findings of this study demonstrated that subjects with flat feet had a lesser activation in PL muscles as compared to subjects with normal foot curvature. Therefore, it is necessary to incorporate strategies to improve the strength of these muscles to improve the arches of the foot.
