What Is the Stretch-Shortening Cycle of Muscle Action?

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What Is the Stretch-Shortening Cycle of Muscle Action?

A muscle usually has two different types of action – stretching of the muscle and shortening, known as eccentric and concentric, respectively. When an exercise employs both types of actions, such as in jumping, running, throwing and other exercises that stretch and then shorten the muscle quickly, it is called the stretch-shortening cycle (SSC). So the question most asked is “Why is this important to know?”

A muscle usually has two different types of action – stretching of the muscle and shortening, known as eccentric and concentric, respectively. When an exercise employs both types of actions, such as in jumping, running, throwing and other exercises that stretch and then shorten the muscle quickly, it is called the stretch-shortening cycle (SSC). So the question most asked is “Why is this important to know?”

 

The answer is because the SSC is synergistic making it more efficient than using just either stretching or shortening alone. For example how far could a soccer ball player kick the ball without first bringing back the kicking leg? Not very far. Try it. Place a ball on the ground and from the standing position, bring your leg forward and kick the ball.

 

But by first bringing the leg back (eccentric) and then rapidly shortening those stretched muscles (concentric) by bringing that leg forward, the energy release is greater. Try it again. See the difference?

 

Another example is the vertical jump. How far up can you jump from the standing position? Not far right? Now first bend down at the knees and then jump up. You should be able to jump a lot higher. The key to the efficiency is the transfer of energy from stretching to shortening has to be immediate. If not, the stored energy is absorbed by the stretched muscle.

 

For example, bring one leg back as if you were going to kick a ball. Now instead of immediately bringing that leg forward, keep it stretched back for a couple of seconds. Now bring it forward. Notice how much of the forward power had diminished?

 

In weight training, the bench press is a good example of a measured loss. A one second delay at the bottom of a bench press results in a 55% loss of force than if the weight was immediately pushed back up once at the bottom of the press.

 

Exercise routines that employ the SSC concept are known as plyometric and come in upper and lower body, along with trunk. To benefit the most from plyometric exercises, the muscles used should have from 24 to 48 hours of recovery between sessions.

 

Because plyometrics is a form of resistance training, all routines should employ the progressive overload concept meaning the systemically increasing the frequency, intensity or volume of the type of exercises performed. As with all exercise routines, SSC types should begin with a warm-up and end with a cool-down.

 

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