Updated: September 5th, 2021

Impress your run coach by understanding how we produce high magnitude forces during running. This little secret will make running effortless, but entails some work on your part…

Why exactly are we talking about this?

Well, biomechanics is a science that helps us to understand how the body moves and manage forces. Throughout movement, we have to deal with both internal forces (produced by muscles) and external forces (ground reaction forces) for peaking our biomechanics, and making running easy-peasy.

For any sport, optimising biomechanics is crucial, this fluidity in movement means we as athletes use much less effort to move our body. And how do we do this exactly?

The answer: The Stretch shortening cycle.

This Stretch shortening cycle (SSC) is not limited to a particular muscle or a specific activity; it is involved in every human movement that involves a change in direction, like walking, running, jumping and twisting. It is in the innate ability of our Stretch shortening cycle that proves us with the efficiency in almost every sport movement, but particularly running.
Sprinting man on a beach
Here, we’re talking about the science of SSC, its implications and discussing the significance of SSC in running, ending with the most effective training drills you can do at home to further develop the skill and transform your running performance, like a piece of cake.

What is the ‘stretch shortening cycle’?

Well, scientifically, SSC is a cycle comprised of three phases. They are:

    Eccentric phase – The lengthening eccentric contraction of a muscle, for example: the lengthening of the quadricep muscles during initial squat-like loading for the jump.

    Amortisation phase – the transition period, where a time delay between loading the tendons with energy to the pre-burst of force generated. for instance; the end of the eccentric contraction of the quadriceps squat loading phase and just before the spring up to jump.

    Concentric phase – the concentric contraction from the same muscle lengthened in phase one. Unleashing the generated energy. For example, the quadricep concentric contraction, causing a powerful knee extension (as part of the triple extension of hip, knee and ankle into a jump).

stretch shortening cycle diagram

This whole cycle works exactly like a spring; upon compression it stores elastic energy and upon release of the compression, a spring rebounds with substantial force.

The harder the amount of force applied, the higher will be the rebound of spring.

Similarly to the spring, our tendons (the tissue connecting muscle to bone) have elastic properties and have the ability to store elastic energy but not generate it. Tendon’s cannot be voluntarily contracted, so they remain in the state of tension – it is the muscle that has contractibility properties.

Your muscles must remain eccentrically contracted during the first two phases of SSC (eccentric phase and amortization phase) to transmit forces to the attached tendon.

This leads to the lengthening of tendons along with storage of elastic energy. Immediately followed by concentric contraction (which incidentally gets boosted by release of energy) for powerful propulsion in the air.

Voila! well done you and your biomechanics.

Stretch shortening cycle in running

Running mechanics should be economical, free-flowing and natural. The Stretch shortening cycle during running, demands concentric muscle action only once – during the stance phase of running; SSC handles the rest of the sprinting cycle.

The absorption of energy (between 2500 to 3500 Newtons, to be exact) is done during the braking phase and then re-generating it during the propulsive phase of running mechanics; a spring in your step, if you will.

So it is vital to work on your SSC optimization for achieving a proper running economy, but be warned, the SSC energy has a short life of just 850 milliseconds?! So we need to utilise it so fast; use it or lose it!

Another important point is input force or loading rate during the initial eccentric phase; it is crucial for enhancing the output in running. The higher the loading rate, the greater the running performance. So, an initial phase of loading is a critical contributor toward performance enhancing the Stretch Shortening Cycle effects.

Types of SSC

Accordingly, SSC can be divided on the basis of time frame. There are two types of Stretch shortening cycles;

    Slow SSC – (Slower movements utilize slow stretch shortening cycle and has duration of above 250 milliseconds)
    Fast SSC- (Faster movements have a time frame less than 250 milliseconds)

Whilst running, we utilize fast Stretch Shortening Cycle for peak performance*

Optimization of SSC for high performance in running

Remember that in-born SSC ability we have?
To improve it (and with it our running capabilities) we must work on good loading rates during the initial eccentric phase of SSC; The higher the loading rate during the active phase, the better the rebound effect during the third, concentric phase.

So here’s the secret; runners must incorporate plyometric training programs for enhancing SSC biomechanics.

Women training

Athletes must also be trained eccentrically, by strength and power programs. In this way, optimization of SSC in runners ensures high performance, at a lower energy cost. Instead of burning up and burning our chemical energy, an efficient stretch shortening cycle means energy is generated without us actually doing anything. We’re just going with momentum (as one muscle contracts the other lengthens and propels us forward, causing the opposite to contract and so on).

How plyometric workouts optimize SSC?

Plyometric workouts use exercises to produce maximal force in the shortest possible time, within your muscles. As you already know, all dynamic movements utilize SSC.

So, the better the optimization of SSC, the better your performance.

Plyometric workouts enhance the Stretch shortening cycle by speeding up all three phases. As an obvious result, the overall dynamic movement like running becomes more efficient, fluid, natural and explosive.

Some of the most popular plyometric workouts include:

Of Course you can incorporate these exercises into a High intensity interval training (HIIT) regime alongside your running training plan, find out how [here].

Happy jumping! and remember to warm up first!

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