Almost all of us see—or participate personally in—static stretching before engaging in strenuous exercise of most types. By stretching, I mean slowly moving muscles until they just start to hurt and then holding the stretch briefly. The reasons for stretching are presumably to reduce the chances for injury and to increase performance. Although we in medicine have long recognized that little scientific evidence supports these assumptions, recent evidence indicates that stretching not only fails to prevent injuries, but actually impairs strength and speed in some athletes. Thus stretching should be limited or excluded before most physical activity.
One recent study, published in the Journal of Strength and Conditioning Research, concluded that if you stretch before you lift weights, you may actually feel weaker and wobblier than you would have otherwise experienced. This added to accumulating prior data that support a scientific consensus that stretching is not only useless but actually likely counterproductive.
With regard to exercises of strength, e.g., weightlifting, reviews of multiple past studies have shown that prior stretching actually reduced lifting power by as much as 5-8% when those who stretched were compared with those who didn’t.
This information merely confirms what most physical trainers have already long put into practice. Most suggest just a little light and brief stretch beforehand, and spending more time on recovery stretching afterwards. This group has long felt that the best time to stretch is after exercise, but even this assumption lacks a sound scientific basis.
So stretching has long occupied an indelible part of the preworkout routine for misguided reasons: Although it seems to help in a limited degree with flexibility and improve range of motion, many falsely equate stretching with the warming up of muscles. This latter activity is useful and well established. For example, tennis players require a few minutes of prior motions of various strokes, and relief pitchers need a few minutes in the bull pen before entering a game. Thus the warm-up phenomenon is well established in virtually all sports in order to enhance initial performance. But there is little evidence that either warming up or stretching prevents injuries. In contrast to warming up, stretching is potentially harmful to muscles because they may actually lose flexibility when they are overworked, and this can lead to reduction of power.
But stretching isn’t all bad, for it can give non-competitive people a wider range of motion in their joints, which can help them to perform their daily activities and improve balance and posture, which can aid in preventing falls and other injuries as people age. But, as noted, the risks of stretching include decreased strength, especially in weight-bearing activities. Those who are recovering from injuries, in which there may be considerable scar tissue that limits range of motion, may also require a bit more stretching to prevent further damage to the areas involved.
So, in summary, when it comes to preparing for a workout, one should consider warming up the body rather than simply stretching muscles. That means adding exercises in addition to light stretching, like motions simulating the imminent activity, which can prepare the body for intensive motion without making the muscles vulnerable to overwork.