The Stretch Shortening Cycle

I have discussed the SSC in bits and pieces in a few blog post discussions. In this discussion, I hope to go a little deeper into what the cycle is. The stretch shortening cycle is utilized by the rapid lengthening of muscle fibers (eccentric action) a very short transition phase (amortization) and a rapid shortening of muscle fibers (concentric action). It is key that the cycle is fast, because without the speed of the muscle action, most of the energy generated would be lost as heat. Think of a rubber band, stretching the band creates potential energy, and when it is released, a rapid shortening that occurs. The muscle acts similarly to the rubber band, except the muscle must transition from a lengthened position to a shortened position quickly. 

Power is how much force can be generated as quickly as possible. Therefore, power capabilities of an athlete is dependent on the stretch shortening cycle. There is a reason that power-lifters are not world class sprinters! I mean, there are several reasons, but one of the glaring reasons is that training for these two sports is totally different. In a 1 rep max (1RM) squat event, the athlete essentially has “unlimited” time to complete the lift. The heavy load slows the movement down to a snail’s pace and time for force production is way longer than 250 ms, and the utilization of the SSC is limited. On the other hand, the sprinter has a finite window to produce the force required to get down the track as fast as possible. So, they never have the opportunity to produce maximal force like the power-lifter, and they are absolutely dependent on the capability of their SSC.

So, how does this relate to the “false step” discussed on instagram? Well, that step provides a couple of crucial elements to sprinting. One of those elements is the rapid stretch and shortening of the calf (SSC)! The role of the calf musculature (triceps surae) to induce plantar flexion in the late ground contact phase of walking and sprinting, or “toe off.” How do we get more force production out of that contraction? Stretch it real quick, that’s how! A lot of you have probably heard the cue from coaches “keep the toes up” when sprinting. This is an important cue for a couple reasons, dorsiflexion (toes up) stretches the triceps surae and utilizes the SSC over and over again. It also preps the foot for ground contact to minimize breaking affects. This concept, along with the concept of the “false step” and how it lines up the body for acceleration, will be discussed in a future blog post introducing sprint mechanics. 

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