Stretch Shortening Cycle

301.4

box-jumps

The fundamental elements of human power production are: high-speed strength, low-speed strength, speed of force production, strength-shortening cycle and muscle memory or skill. The first three elements are trained in the gym, the fourth is a gift of nature and the fifth means that you could be the most perfect physical specimen ever to walk the earth and you wouldn’t be able to chew gum and walk, unless you practiced chewing gum and walking, of course. Let’s talk for a moment about number 4.

Do you remember the classic scene in the doctor’s office where the patient is sitting on the exam table and the dr. hits his knee with a rubber hammer and the patient’s leg kicks out? That is a demonstration of the stretch shortening cycle. A perfect example of the body’s defense mechanism against overstretching, when the hammer hits the tendon over the knee and quickly shortens the quadricep muscle, the brain immediately tells the quad to contract and simultaneously keeps the opposing muscle, the hamstring, relaxed so that there is no opposition to the leg’s movement, preventing overstretching. The same phenomenon can be seen in weight training, called ‘bouncing out of the squat’, the athlete lowers the weight under control until, at the very bottom of the squat the pre-stretched muscles rebound to start the weight up again.

The stretch shortening cycle is a built in part of the human machine but knowing what it is and what it does can help us in getting to know our bodies better. Plyometrics is a subject that really embraces the stretch shortening cycle, many of the movements rely on it for their effectiveness. One of my favorite exercises is platform jumping or box jumping. Many people do this in their workouts, but there are two ways to do this and two very different results.

The basic box jump starts with the athlete standing in front of a wooden platform and jumping from the floor to the top of the box, fully extending the hips each time and jumping back down to the floor. If you can do this, awesome. Now think about this, start on top of the box, jump to the floor and spring back onto the box without pausing at the bottom. This is where the stretch shortening cycle lives. Try this ten times with a small box or snatch block, 6 to 8 inches tall to begin with. Rest at the top instead of the bottom if you need to and try to keep your heels from touching the ground when you land at the bottom, this leaves all of the stretch in your legs. The first several times be careful as there is a component of skill and balance involved in getting back to the same spot you started each time. Think unicycle, don’t hurt yourself trying to help yourself.

workout: run 1 mile, no stops

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