Since 1980, according to several authors, it is accepted that increasing flexibility of a muscle-tendon unit allows a better performance and decreases sports injuries. Stretching is regularly included in warm-up and in cooling-down. However, there are contradictory findings in the literature. In contrast, since 1990, there's evidence suggesting that stretching not only does not prevent injuries, but can also decrease the level of performance. Some part of these contradictions can be explained by the various sports activities. Those requesting an increased flexibility, such as gymnastic, dancing or diving, necessitate pre-exercise stretching to optimize the level of performance. In contrary, for sports with slow stretch-shortening cycle such as jogging or cycling, there is no scientific data showing a positive effect of stretching.