Being a foot is a hard job!
Our feet are exposed to high loads every day. On our feet, we walk almost half of the earth's circumference in our life. Our feet ensure that we stand in a stable position, and they adjust to the unevenness of the ground. They have special shock absorber functions to cushion our steps. With every step that we take while we walk, a foot bears at least the person's body weight. As our motion speed increases, the foot bears between two and five times our body weight (slow runs versus fast runs). If we consider the daily load that the feet bears while walking, that load can easily exceed 600t if the person's body weight is 75kg. If the marathon distance of 42km is run at a total time of 4:30 hours, this corresponds to a load of over 3000t on each foot – which is equal to the weight of 1.000 average elephants!
Adjusted to upright walking
The shape and function of the foot are closely related to each other and make the foot's structure so unique. For about 3 million years, that structure has adjusted to upright walking on two legs. Today, our entire body weight is only borne by two feet instead of four. The body's centre of gravity has shifted upwards so that keeping one's balance has become considerably more complicated.
Feet – the only interface between the body and the ground
As the characteristics of the ground vary quite strongly occasionally (forest soil versus pavements), the foot must, on the one hand, be flexible and soft in order to adjust to uneven ground. On the other hand, it must be rigid and solid in order to transmit the force of the leg muscles to the ground. Here, the sensory feedback system of the foot is very helpful: You simply walk differently on sharp stones or hot ground. Thousands of nerve cells supply the central nervous system with information on the characteristics of the ground and the position of the foot and thus have a regulating effect on the movement sequences of the body. Therefore, the foot is often referred to as a "sensory organ" which, thanks to its complex functionality, fulfils the necessary requirements for everyday life and sports. In addition, each foot has about 90,000 sweat glands.
The skeleton of the foot consists of 26 bones, 33 joints, over 100 ligaments, 30 muscles and 60 sinews. Functionally, the foot is divided into three areas: hindfoot, midfoot and forefoot. Altogether, both feet contain about a quarter of all bones of the human body (about 208 bones).
In the back area of the foot, the bones are located above each other; however, in the middle and front areas, they are located next to each other. This creates a distinct longitudinal arch on the inside of the foot and a transverse arch running from inside to outside on the back part of the midfoot.
In close contact!
It is often written – wrongly – that the foot mainly rests on three points in standing position: the heel and the joints of the big and little toes. However, in measurements of the pressure distribution between the foot and the ground/shoe, it was found that the foot always has full ground contact when it bears loads in the area of the metatarsophalangeal joints. It can therefore be said that the model of the bearing on three points is outdated.
A shock absorber in the foot?
Foot arches are braced by ligaments and sinews and stabilized by muscles. They preserve the arched shape and form the basis of the perfect functioning of the foot. The main purpose of foot arches is to take and transmit loads while walking or running. If the arch is squeezed due to the load when the foot touches the ground, the bottom of the arch is stretched. If, however, this function is impaired, e.g due to weak foot muscles, the foot arches become lower in the long run and the shock absorption is restricted.
I) The foot arch types: normal, flat, high
Foot arches can have different heights. This may be due to inheritance, overweight, or more or less trained foot muscles. Shoe soles that are too stiff cause the foot muscles to atrophy so that the foot arch becomes lower. As you get older, it might even be possible that you will need longer or wider shoes due to the foot arches becoming lower. After all, your feet bear several 1,000 tons of weight over the years! Therefore, well-trained feet have a better ability to bear a foot's everyday loads and to protect against injuries. However, due to their more distinct muscles on the bottom side (which can be seen in footprints, for example), such well trained-feet often resemble feet with a flat longitudinal arch although they do not have one.
II) The foot shape types: Egyptian, Greek and Roman
According to the difference in length between the big toe and the second toe, three foot shapes are distinguished:
Egyptian foot: The big toe is the longest (about 50%* of the population).
Greek foot: The second toe is longer than the big toe (about 40%* of the population).
Roman foot: The second toe and the big toe have the same length (about 10%* of the population). The names of the three types have been chosen according to depictions of feet and ideals of beauty in the ancient world.
*The percentage distributions vary according to the source of information.
Cushions of fat at the right places are good!
Under the foot, in the sole, very important cushions of fat are located. They support the redistribution of the load while walking or running. The layer of fat consists of separate chambers that are moved against each other and compressed when they are exposed to loads.
Rolling over naturally is healthy!
All muscles and sinews contribute to the load being distributed evenly over the whole foot when walking – from the heel touching the ground to the outer edge, the outer ball, the metatarsophalangeal joints, the inner ball, and the repulsion over the big toe. While children up to the age of 10 touch the ground with almost the whole sole, rolling over automatically is natural for adults. But this is exactly what many shoes prevent – many shoes support the foot far too much. In that case, no more demands are made on muscles and sinews, and they atrophy. This can have negative effects on the entire locomotor system.
But soon there will be a solution! Baak has developed safety shoes that are optimally suited to the foot and allow it to move naturally – which has positive effects on the entire locomotor system.
A useful contribution to workplace health promotion. Available from Autumn 2015. Developed in cooperation with Prof. Dr. Gert-Peter Brüggemann, one of the world's leading biomechanists. Are you interested?