How well are we equipped to run? - 2. Lower legs and feet. April 12 2016, 0 Comments
From our previous discussion, our upper legs are designed to help us with locomotion on the ground, and I'd like to now build the case that we are actually designed to run.
Casting our attention south to the lower legs and feet, and again comparing with the apes, we can see that we have a very chunky calf muscle and a considerably bigger achilles tendon.
Tendons connect bones to muscles and are elastic, often being placed to absorb and store energy for later use. For walking, where we normally plant the heel and then roll forward on the foot to pushing off into the next step, there doesn't seem to be much need for a large, impact-absorbing tendon. For running, on the other hand, especially if we accept the case for a front-foot landing, the absorption of energy as the heel is lowered warrants a very much larger tendon, such as we have. The elastic energy stored can then be used for the push-off into the next stride.
The case becomes stronger when considered with the structure of the foot. One of our feet has 26 bones, 33 joints and more than 100 muscles. Many of these are located in the arch, which acts as a bridge between the ball and heel of the foot. When we land on the front foot in running, the muscles in the arch and the achilles tendon together tense and absorb the impact of the step so that the heel lands much more lightly. This prevents a jarring impact at the heel being transferred upwards to the ankle and knee and the lower back. One of the best illustrations of this are the videos taken by Dr Daniel Lieberman's group at the skeletal lab at Harvard University. Follow the link for a heel strike. You can see that the total impact of landing is about two and a half times the body weight, when the heel lands about one and a half times the body weight occurs in the first, jarring impact by the heel, shown by a vertical line on the impact/time trace at the bottom.
With a front-foot landing, the impact trace has a much more gradual slope, showing a steady transfer of weight, rather than a sudden one. Furthermore, adding a big wad of padding to the sole of your foot doesn't significantly reduce the sudden impact of a heel strike.
So our calves, achilles tendons and feet are admirably suited to provide us with a cushioned ride during running. And we have other equipment that helps us to run, as we shall discuss in the next blog. In the mean time you might like to check out our ZEMgear shoes, which protect your feet, but allow them and your legs to run as nature intended.