# A Novel Wearable Foot and Ankle Monitoring System for the Assessment of Gait Biomechanics
## 4 Discussion  
Standing of humans is performed using sensory information from the ankle muscles, provided mainly by the gastrocnemius, soleus and tibialis anterior. While standing, muscle activation depends on the position of the COP. For balance, when the body sways forward and the COP moves forward, the gastrocnemius and the soleus are activated. When the body sways backwards and the COP moves backwards, the tibialis anterior is activated. In muscle activation, autogenic reflexes for postural control are particularly important [54]. Gait is an even more complicated process in comparison to standing. It needs the neuromuscular systems to control the body along with a healthy and functional skeletal system. A good muscle ankle control is essential both for maintaining stance and for gait. In this context, the proposed foot biomechanics wearable monitoring system provides a viable solution for the assessment of both plantar pressure distribution along the COP progression line and lower-limb muscular activity via two EMG channels. Through EMG recordings, our study sustains that ankle movement in the sagittal plane during the stance phase is controlled by the interaction between agonist and antagonist muscles of the leading limb. Both relaxation of the gastrocnemius and contraction of the tibialis anterior, which dorsiflexes the ankle, make the heel strike possible by the fact that the COP is brought posterior to the ankle. For the remainder of the stance phases, the two muscles work in opposite phases, enabling the advancement of the COP through the forward rolling of the foot. Visualization of this phenomenon is enabled by the proposed distribution of the pressure sensors on the shoe insole. During the forward rolling of the foot, which implies ankle plantar flexion, the COP progresses anteriorly from the heel, yet not in a straight line due to the frontal plane movements of the foot, i.e., supination and pronation. During the stance phase, the last point of pressure is the toe, when the swing phase follows toe-off. Tibialis anterior contributes to the dorsiflexion of the foot in the pronation of the foot. A novelty of the work proposed in this paper is the underlaying software application which performs the cross-correlation of the plantar pressures, specifically the progression of the COP, with the lower-limb muscular activity. The cross-correlation results in a matrix representation of the gait pattern, i.e., the proposed gait map. Objective gait evaluation is then performed by comparing the gait map to a reference map of the physiological gait. As such, our study reveals a healthy muscle activity pattern for the investigated ankle and 'foot. Our tests were carried out under the assumption of healthy lower-limb muscles. As such, the AFE gain was set to amplify the nominal 1 uV-10 mV EMG amplitude range into the +/ - mV amplitude rage prior to ADC. At this stage, a discussion worth having regards the variation of the EMG amplitude as a result of muscular disease and its effects on gait assessment using the proposed system. Under this gain configuration however, small EMG amplitudes will not be sensed by the AFEs employed in the proposed system, whereas large EMG signals will determine features outside the ranges listed in Table 4, leading to erroneous identification of walking. To counter such effects, gain adaptation techniques, e.g., [55], can be envisioned for the proposed system. Another discussion regards the effects of noise and EMG artifacts on the operation of the proposed system. A noise-free EMG signal, containing only information regarding muscular activity, accounts for the ideal operating conditions for system operation. The presence of artifacts however may determine features outside the ranges listed in Table 4, thus leading to erroneous identification of walking.