Run Faster, Jump Higher Utilizing Your Body’s Elastic Energy by Matt Jessee
[This is a guest blog by one of our Athletic Interns, Matthew Jessee, an Exercise Science student from Appalachian State University]
Have you ever wondered why a kangaroo hops? They are utilizing the elasticity of the tendons in their legs. This allows them to not only jump higher and cover long distances quickly, but they are able to do this without expending very much energy which is critical when living in harsh conditions. They do this using the powerful tendons in their legs. Humans might not be able to jump 20 feet in a single bound nor run at speeds at 40mph, but we can utilize the same principles to enhance performance.
The basic anatomy of skeletal muscle has a tendon attached to either side of the muscle which connects both ends to different bones. When the skeletal muscle contracts (or shortens) it brings the bones closer together decreasing or increasing a joint angle. These muscles and tendons have elastic properties similar to a rubber band. Imagine taking a rubber band and stretching it far apart, then letting it snap back. There are three phases to the stretch-shortening cycle. We will use a vertical jump to discuss these phases.
The first is the eccentric phase, or the countermovement. This simply means you are stretching the involved muscles and tendons. In the vertical jump this would be squatting down before jumping upward. Think of the rubber band the further you stretch these muscles and tendons the more energy you are storing to jump higher in the concentric phase. During this stretch you are pulling on specialized muscle fibers called muscle spindles that detect tension in the muscle. When a stretch in the muscle is detected it activates a reflex which causes the muscle to contract with a large amount of force.
The concentric phase is the contraction of the muscles required to perform the movement; in this case a vertical jump. During this movement not only are the muscles shortening to produce the movement but the tendons after being stretched are returning to their normal length; this adds a lot of extra force to your upward movement compared to just using muscle contraction alone. Remember during this phase the muscles will contract stronger than usual due to the muscle spindles.
The key to harnessing this elastic energy is the amortization phase. The amortization phase is the phase between the eccentric, and concentric phase of the stretch-shortening cycle. Unlike the rubber band our body takes energy to keep the muscles and tendons under tension. If we are in the bottom part of our jump too long most of our elastic energy will be lost as heat, we will lose force and usable energy, resulting in a lower vertical jump. The amortization phase should be as short as possible to harness as much energy as possible. So we should jump vertically as soon as we finish our countermovement. The less time between squatting down and jumping upward the higher our jump will be. Try experimenting with this. First squat down into jumping position and hold for about 5 seconds (the stored elastic energy will be released as heat) then jump. Next try squatting down quickly and immediately jumping as soon as you reach the bottom of your squat. Which jump was higher?
Now that we understand the basics of the stretch-shortening cycle we should train our body to utilize it effectively. One way to do this is to utilize plyometric training within a program. Plyometrics utilize various jumps, throws, and hops performed with countermovement in a quick, powerful manner. This type of training allows one to become more efficient at producing power which is a vital component to many different sports and activities.
