This is an excerpt from Delavier's Stretching Anatomy by Frederic Delavier,Jean-Pierre Clemenceau & Michael Gundill.
How an Athlete Should Stretch
There are two primary techniques for athletic stretching.
Static stretching consists of holding a stretch for 10 seconds to 1 minute. The degree of stretch can be from very light to rather strong depending on your objective.
Advantage: Practiced in a controlled and progressive manner, static stretching is very unlikely to cause an injury.
Disadvantage: This type of stretching is most likely to cause a decrease in performance when done just before a workout.
Dynamic stretching consists of pulling more or less forcefully on a muscle using small, repetitive movements for 10 to 20 seconds. This type of stretching resembles plyometrics because it plays on the stretch-relax cycle (or elasticity) and causes a reflex contraction. The goal of the small movements is to force the muscle to lengthen more than it would do so naturally.
Advantage: Dynamic stretching is the least likely to cause a decrease in performance when done before a workout, so long as the muscle does not tear. But you must be extremely careful when doing this type of stretching because it can cause injuries.
Disadvantage: This kind of stretching is the most likely to cause injury.
Generally, you should do 1 to 3 sets of stretches per muscle group. Then the only thing you as the athlete need to do is determine which muscles you wish to stretch depending on your sport as well as your personal needs. To help you in this task, see the variety of programs in the third part of this book (page 127).
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