# A Novel Wearable Foot and Ankle Monitoring System for the Assessment of Gait Biomechanics
###### Abstract
The question which stands at this point targets the deployment of the pressure sensors in order to record the plantar pressure distribution for static, as well as dynamic assessment. Solutions proposed in literature for the static assessment of plantar ground forces assume several pressure sensor distributions presented as follows. A basic solution for the assessment of the body posture assumes three sensors for the forefoot, midfoot and heel respectively, as illustrated in Figure 2a [8]. A somewhat more complex solution was proposed by [PERSON] et al., who deployed three sensors onto the midfoot and three sensors  
Figure 1: Representation of the footprint division into three regions: forefoot, midfoot and heel, with the illustration of the ten anatomical areas accountant for the derivation of lower-limb and whole-body physiological, structural and functional information. onto the heel area respectively, as illustrated in Figure 2b, [6]. It should be noted that the solution proposed by [PERSON] et al. was also employed in walking tests. A different approach for sensor deployment was proposed by [PERSON] et al., as illustrated in Figure 2c, who envision two sensor clusters in the forefoot and heel area respectively, thus being able to estimate the center of pressure in each cluster respectively [9]. This solution was further aimed for plantar pressure assessment during training room exercises, namely squats and weightlifting. Walking is a cyclic pattern of movements, and as such, human walking analysis can be simplified by investigating one walking cycle--which is measured from the heel strike of one foot to the next heel strike of the same foot. One gait cycle consists of a stance and a swing phase respectively. The breakout of the gait cycle into six sequences is illustrated in Figure 3 for left leg (LL) stance. The left arm (LA) balance is also illustrated for clarity. Figure 3: Breakout of a walking cycle for left leg (LL) stance into six sequences: (**a**) gait phases with the illustration of left arm (LA) balance and the oscillations of the body center of mass, (**b**) progression of the center of pressure with red circles indicating applied pressure. Figure 2: Solutions of pressure sensor deployment on the footprint for static assessment: (**a**) three sensors deployed onto the forefoot, midfoot and heel [8], (**b**) three sensors for the forefoot and heel respectively—this solution was also employed in walking tests [6], and (**c**) sensor arrays deployed on the forefoot and heel to estimate centers of pressure—this solution was also employed in training room exercise tests [9]. The sequences of the gait cycle account or heel strike (1), support, i.e., foot flat (2), midstance (3), heel off (4), toe-off (5) and swing (6). The average duration of one gait cycle ranges from 0.98 to 1.07 s. The stance phase is the period that the foot is on the ground and accounts for approximately 60-62%, i.e., 0.59 to 0.67 s of the gait cycle, during which the foot is weightbearing as the leg takes the bodyweight and provides a single leg support. The remaining 38-40%, i.e., 0.38 to 0.42 s of one gait cycle is spent in the swing phase, which is the period of time that the foot is off the ground, moving forward and the limb advances [10; 11]. During the gait cycle, pronation and supination normally occur in the foot segment. Pronation and supination are necessary for shock absorption and stability mechanisms for the healthy functioning of the feet and ankles. During the stance phase, the bodyweight travels along the foot, as indicated in Figure 3b illustrating the COP progression line. Physiological walking assumes that the weight moves inside and outside while the foot is rolling from the heel towards the toe. The pronation corresponds to the moment where the foot is in contact with the ground and begins to roll inward, everting slightly while the arch flattens. The purpose of the pronation is for the foot to be able to adapt to the surface. After the pronation, the foot continues towards supination.