Developing the Stretch-Shortening Cycle

Why Be Bouncy?

Elasticity is a vital component of athleticism. The faster one can go through the stretch-shrortening cycle (SSC), the faster off the ground they will be. This leads to faster sprint speeds and faster/higher jumps. It also leads to more efficient movement. The less time spent on the ground, the less muscle shortening there is, and therefore the less energy is spent on each step. So a better development SSC=faster and more efficient movement. 

It is also important to note that dependence on SSC increases with speed. After the 3rd step of acceleration, the ground contact times are too quick for voluntary concentric muscle actions. This means that force production is dependent upon storage and release of elastic energy via a fast amortization phase. For sports that involve high speed movement (American football, soccer, rugby), the majority of locomotion is dependent on a fast SSC, being able to store and release elastic energy within the tendon at a fast rate. 

Structure 

Structure dictates function. Structure refers to muscle cross sectional area(CSA) and tendon stiffness. Increasing muscle CSA improves force production potential, as it allows for a greater amount of fibers to pull from. Tendon stiffness is of the utmost importance in regards to SSC actions. The stiffer a tendon is, the more faster force will be transferred from the muscle to the bone, leading to faster ground contact times. A stiffer tendon will return more elastic energy following being stretched than a more compliant tendon. 

This comes from heavy, slow resistance training. The tendon needs to be put under strain to create structural adaptation. Therefore, the intensity level needs to be high. It has been shown that 70% maximal muscular contraction is needed for collagen synthesis. However, the movement speed needs to be relatively slow in order for the tendons to experience a viscoelastic effect, resulting in deformation. Slow speed can be accomplished through adding resistance or performing a controlled eccentric. This is best accomplished through traditional resistance training that can be progressively overloaded over time. 

Function

Function refers to the coordination involved with being quick off the ground, the skill of elasticity. There is a rhythm and timing component to utilizing the SSC effectively. Muscles must contract and relax at the proper time to get the most out of the ground contact. The athlete must pretense the muscles prior to ground contact, then remain isometric upon ground contact to allow the tendon to do its job of storing and releasing elastic energy. Body awareness in space is also necessary, as  joint misalignment will increase ground contact time, and therefore reduce movement speed and efficiency. 

There is a disconnect between weight room strength and elastic strength. Weight room strength depends on sustained muscular force through a large range of motion, while elastic strength depends on quick bursts of muscular tension and relaxation with proper timing. This is why there are athletes who lack impressive weight room numbers, but excel in dynamic movement on the field of play. Therefore, we must expose athletes to plyometric ground contacts to use the structural adaptations built in the weight room

Just like any skill, elasticity is improved through repetition. This is done through accumulating a high volume of elastic ground contacts. Start with extensive variations of plyometrics, then gradually increase the intensity. Athletes who are not strong in the weight room but display great elasticity do so through elite timing and rhythm. There is no other way to develop this timing and rhythm than through repetition of elastic ground contacts. 

Summary

Being quick off the ground via the SSC is vital in athletic performance. It allows for faster and more economical movement. The structure must be built through lifting weights under high tension. Most importantly, that structure needs to be used in the context of elastic plyometrics, building the rhythm and timing necessary to get the greatest elastic energy return upon ground contact.