The Biomechanics of the Foot

The following is an article written by Ray Anthony a recognised leader in Podiatry and foot Biomechanics:

“If modern engineers designed the human foot, we would have no structural problems and our feet and legs would function perfectly. They would make us perfect walking and climbing machines with minimal risk of imbalance and injury. Imagine no risk of ankle fracture or sprain, no heel pain, no arch strain or soreness under the forefoot, not even the chance of a blister!

The human foot is an amazingly complex piece of bioengineering. With 26 bones, 55 joints and a complex system of ligaments, muscles and tendons. At initial heel contact, the foot has to endure forces often in excess of 3 times body weight! Unfortunately for us, its construction is one that has evolved rather than having been specifically designed. Due to genetic differences, previous injury and sometimes systemic illness, our feet and legs are often structurally and mechanically compromised. Many of us are unknowingly designed with small intrinsic structural abnormalities that make us prone to foot and lower limb problems that can ultimately cause injury and stop us participating in our sport and leisure pursuits.
It is widely accepted by biomechanics specialists that the most common structural problem suffered by the general population is excessive foot pronation. If your heel rolls inwards too much, excessively lowering the arch of your foot and making your ankle bulge on the inside, you have excessive foot pronation! Research has shown this biomechanical condition to be a common cause of many foot and Leg injuries in active individuals, including walkers and climbers. The most common foot problems associated with excessive foot pronation include arch strain (plantar fasciitis), heel pain (plantar calcaneal bursitis), pain on the ball of foot (metatarsalgia), inner ankle pain (deltoid ligament strain) and shin splints (tibialis posterior tendinitis). Excessive foot pronation may also cause the leg to rotate inwards too much during walking and mountaineering, causing abnormal twisting forces within the knee and hip.

The problem with hill walking and mountaineering is the need for the foot to adapt to a variety of different inclines and foot placements. If you were traversing even a gentle slope in a soft and unsupportive boot or shoe, the lack of support would mean that the boot (and your foot) would tend to roll to stay in contact with the surface. If this rolling action was exacerbated by inherent excessive foot pronation, then severe stresses would be placed on the ligaments, muscles and tendons on the inside of the ankle, shin and knee, resulting in potential pain or injury. A further problem for many backpackers and mountaineers is that the rucksack and equipment they carry increases their overall body weight adding to the stresses placed on the feet.

In designing a good walking or climbing boot it is important that certain features are incorporated in its construction. Ideally, it should he formed around a well designed last and be made from good quality, supportive materials (too many cheaper items of footwear are either poorly lasted or use inferior leathers and materials which will not provide adequate support). The sole unit should have a correctly designed tread configuration to offer non-slip stability on irregular and unstable surfaces. It should incorporate a strong, protective toe box to prevent stubbing and bruising of the toes and it should be padded, lined and have a good quality footbed to cushion the foot and protect against friction irritation. However, one of the most important anti-pronation features of a walking and mountaineering boot is the midsole. If this is too soft, the heel will simply push through it and roll inwards excessively during the heel strike phase of walking. A good midsole should have a good level of torsional rigidity and give full support to the heel and prevent excessive foot pronation by creating a stable platform for the foot on steeper slopes and unstable terrain. This is biomechanically more important than any amount of soft, comfortable cushioning. The forefoot of the midsole may vary in its flex depending on the application of the boot. Mountain boots tend to have a stiffer flex down their length for added foot support, whereas many walking boots have a greater degree of flex for walking comfort. One of the things that has impressed me about Scarpa boots is that they have designed different types of graded midsoles to suit the end use of their boots.

To add to the protection given by a good mid sole, I believe that a quality boot should also have a good heel counter and a high quality upper to help prevent excessive foot pronation, lateral ankle instability (twisting of the ankle to the outside) and thereby help to reduce the risk of ankle sprains when walking and climbing on uneven surfaces”.

RaymondJ. Anthony, BSc (Hons), DPodM, SRCh
Podiatrist and Specialist in Biomechanics