One of the key factors in becoming more mechanically efficient while sprinting is having a lot of muscle stiffness at initial contact. The instant your foot hits the ground, your muscles need to be very stiff all the way up the chain (From foot to upper body). The reason for this is simple, energy…or the transfer of energy to be more specific. Thanks to the works of brilliant minds like Frans Bosch we have a stronger understanding of the bio-mechanics of running. In this article we will discuss the importance and the reasoning for having a stiff musculature while sprinting.
Lets start with the energy concept. If we are able to use more of the energy in the environment, then, we will spend less muscle power, making us more efficient. When our body needs to move, our muscles generate power; spending energy, to move limbs necessary for motion. What if it were possible to cut down on the amount of muscle power needed to move? Would this mean that we can use the energy in the environment to move? Yes.
Frans Bosch has described different parts of our bodies as elastic and others, well, not as elastic. Tendons, fascia, and other rigid structures are very elastic (These are the elastic components). Muscles are not as elastic (These are the contractile components). So, if we are able to let the elastic components do the work, the contractile components (Which spend energy), have less of a requirement to fulfill to move the limbs. When a muscle is isometrically contracted there is no movement in the muscle. This means the contractile components must move. If the muscle is not trained to isometrically contract, then the muscle will move (We call this slack), putting less demand on the elastic components. When muscle slack happens, we lose the ability to store elastic energy throughout the system. We want the elastic components of the system to have a high demand on them, leaving the contractile components with a lower contribution to the movement of the body.
Let’s start with the initial contact of the foot. The moment the foot hits the ground we have kinetic energy. If the muscles are stiff and rigid, then that energy gets converted to elastic energy and it shoots up the chain. When the energy traveling up the chain hits a non-stiff contractile component it is absorbed. If we have a completely rigid foot and leg, we conserve all of the elastic energy until we hit the core. If the core is completely rigid, then, again, we have complete conservation of elastic energy. Now, we hold a rigid musculature and transfer all of that elastic energy into the opposite leg. From here we convert the elastic energy into kinetic energy when we hit the ground again. In a perfect world, we use zero muscle power once we hit maximum velocity and utilize the stored elastic energy in our body to move. Being human and far from perfect, we are a long ways from being able to conserve 100% of the elastic energy. Muscle slack, imbalance, poor timing, loos of function all contribute to the absorption of elastic energy in the system. Again, when energy is absorbed, our brain now calls upon the muscles to generate power to create movement. This is okay during acceleration phases, however, it is a killer in max velocity stages of running. It leads to fatigue.
In theory, this seems to be a very simple concept. However, it is extremely difficult to teach the body to hit the ground stiff with the correct timing repeatedly. Concentric lifting, stretching, poor mechanics are just a few of the factors that contribute to the body acting less rigid. The body needs more than just muscle to move efficiently, it needs appropriately trained muscle with the correct coordination and timing. We are currently filming several of our drills that we use to teach stiffness. Our goal is to create high amounts conserved elastic energy within the system, making us run faster using far less energy. Keep in mind, the best runners in the world spend 30% less energy than the rest of us.