Walking and running are essential activities that occupy a big part of life for most human beings. Many injuries can occur if the body posture and movement technique are incorrect during execution of these activities. The whole body participate in the technique, but the feet are probably the most important part, because they are the body fundament.
Biomechanics analysis
The biomechanics of the foot during walking and running consists of many variables like strike, impact force, load rate, range of motion, muscle activity.
Foot strike
Foot strike describes the part of the foot which first lands to ground during walking or running. There are three types of foot strike: rear-foot, mid-foot, fore-foot (Figure 1).
Studies show that runners who wear modern footwear with cushioned padding, usually (85%) land with the heel before lowering the toes (rear-foot strike). On the other hand, barefoot runners usually land with the front foot before lowering the heel (fore-foot strike), or flat foot (mid-foot strike) and less frequently with the heel (rear-foot strike). This is caused, because in barefoot there is no external protection from the shoe - cushioned padding and raised heel (shoe drop). In this way the body adapts to absorb the impact against the ground (1).
Impact force
Figure 2 depicts the impact force on the tibial bone during different foot positions while running. The impact force on the body is distributed by it's absorption mechanisms. There are two types of absorption: active and passive. Active absorption is through joint alignment and muscular forces. Passive absorption is through heel pad, synovial fluid, bone and articular cartilage (2). Studies show that during running with cushioned shoes the knee absorbs more impact energy than the ankle in all foot strike types. On the other hand in barefoot running with mid-foot and fore-foot strike, the impact force is smaller and the absorption is transfered to the ankle, which become the joint that absorbs the most energy. The knee absorbs less energy. It seems that the knee is most benefited when running with fore-foot strike, because it's impact is lower. This can help in improvement of knee injuries. But the impact on the ankle is increased and have to be managed.
It's clear that the foot position and movement technique plays a major role in determining the impact force on the knee, ankle and other body parts during walking and running. It's meaningful to dynamically analyze it in order to monitor and predict injuries. Each human body have it's own unique charactestics and have to be managed individually.
System design
Hardware
Resources
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Lieberman DE, Venkadesan M, Werbel WA, Daoud AI, D'Andrea S, Davis IS, et al. Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature. 2010 Jan 28;463(7280):531-5.
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Ly QH, Alaoui A, Erlicher S, Baly L. Towards a footwear design tool: influence of shoe midsole properties and ground stiffness on the impact force during running. J Biomech. 2010 Jan 19;43(2):310-7.
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Fig.1,2: https://clickphysiotherapy.blogspot.com/