Differences between running and walking in trainers
The stages of running are similar to walking. Walking can be considered as the alternate placement of one foot in front of the other separated by a period of where both feet are on the ground. During walking there is always at least one foot on the ground. However, running has a flight phase, which takes place after the stance phase, during this period neither of the feet are touching the ground. The stance phase during running can be divided into three phases, contact, where the heel strikes, midstance, where there is forward swing of the leg and foot descent, where the two feet are starting to become lifted off the ground. During slower, longer running the stance phase is of longer duration than the flight phase. As, the running speed increases, the stance phase and flight phase become the same duration in length until the stance phase becomes shorter than the swing phase, the person is then considered to be sprinting. Running causes increased in rotation in the joints of the pelvis, hip and knee. This is absorbed by the muscles which are found near these joints.
When running the heel can hit the ground in three ways. A rear-foot strike(RFS) occurs when the heel lands first, a mid-foot strike (MFS) occurs when the heel and ball of the foot land together and a fore-foot strike (FFS) occurs when the ball of the foot lands before the heel comes down. Shod runners often make initial contact with the ground heel first by using RFS. When rear-foot striking, the heels have to deal with a collision force of approximately 1.5–3 times the body weight. For this reason, trainers often have an elevated and cushioned heel design for comfort, stability and to ease the forces of the RFS. However, sprinters, whether shod or not tend to run on their forefeet.
Experienced barefoot runners run using the FFS in order to avoid repetitive, high-impact forces on their legs. Using the MFS or FFS can have a number of advantages. FFS barefoot runners take shorter strides and run with greater leg and ankle compliance because the body’s centre of mass is lowered which results in a smoother movement. FFS and MFS runners do not have to absorb the shock of the heel strike when running and are able converts some of this translational energy that would be lost in the heel strike into rotational energy.
The calf muscles that control the heel drop contain elastic energy within the Achilles tendon, this energy can then be taken utilised when RFT does not take place along with the energy stored in the longitudinal arch of the foot. In order to fully utilise the FFS and MFS, the runners require more calf and foot muscle strength.
Energy efficiency within the foot
The main reason the foot is so energy efficient is because the foot is not flat, the bones fit together and form three arches. The arches can be compressed or stretched when the weight of the body is applied down the foot and the foot is able to spring back when the weight is removed from the foot. This makes walking and running economical in terms of energy expenditure. The foot contains three arch structures, two longitudinal and one transverse arch which also allows it to have great strength. The arch is maintained by the fact that the bones of the foot interlock with nearby bones, ligaments and due to the pull of the tendons of muscles when muscular activity occurs. The foot also has spring ligament which are continuous with the deltoid ligament on the medial side. This is another energy efficient saving mechanism. It stores energy every time you take a step and releases it every time you push off with the toes.