The influence of foot arch on ankle joint torques andon sEMG signal amplitude in selected lower leg muscles

Introduction
This study sought to assess the influence of proper foot arch on electromyographic activity of selected lower limb muscles. The aim of this work was to evaluate the effects of foot arch on the activity of selected muscles and to determine whether electromyography might help to identify types of flat feet resulting from muscle- or ligament-related causes.

Methods
The experiment involved 24 students of the Faculty of Rehabilitation, University of Physical Education in Warsaw. To determine Clarke’s angle,all study participants were examined with a podoscope. Based on the obtained results, the subjects were divided into two groups. The experimental group consisted of 12 individuals with low foot arches, while the control group included students with proper foot arches. The surface EMG /sEMG/ signal was recorded from the following muscles: peroneus longus, tibialis anterior, gastrocnemius and soleus. First, the sEMG signal was recorded while measuring MVC for ankle extensors and flexors. Then, it was recorded in the following positions: free standing, two-leg standing on tiptoe, one-leg standing on tiptoe, pressing the first metatarsal head to the ground standing on heels.

Results
No significant differences in muscle activity between the groups with low and proper foot arches were noted (p>0.05). Muscle activity did not prove to be a differentiating factor. Moreover, no differences were found in torques of ankle extensors and flexors between both groups.

Conclusions
The findings of the study confirmed the hypothesis that the size of the foot arch had no effect on electromyographic activity of lower limb muscles. It was also revealed that flat feet did not lead to the weakening of muscle strength of ankle flexors and extensors.