The only way physios can get a really clear idea of the effects of stretching is to review randomised trials, in which a lottery is used to allocate each participant to either receive the treatment (in this case, stretching) or not. Then the outcomes (injury, muscle soreness or sporting performance) of the participants who stretched are compared with those who didn’t. The difference in the two groups tells us about the effects of stretching.
The first two trials of the effects of stretching on risk of injury, conducted on 2,631 army recruits, showed three months of routine stretching before exercise did not appreciably reduce injury risk. A more recent trial on 2,377 active people had very similar findings: three months of regular stretching had little or no effect on risk. Together, these trials strongly suggest stretching doesn’t appreciably reduce injury risk.
A number of other trials have investigated the effects of stretching before and after physical activity on the soreness experienced after exercise. A review of these trials concluded that muscle stretching, whether conducted before, after, or before and after exercise, does not produce clinically important reductions in delayed-onset muscle soreness in healthy adults.
Flexibility and strength
The effect of stretching on sporting performance is less clear, or at least more complex. Not many trials have measured sporting performance as an outcome. Instead, most have studied the effect of stretching on two factors that are likely to affect sporting performance: flexibility, and the ability of muscles to generate force.
So the first question is: does stretching actually increase flexibility? In the short term, yes. After just a few seconds or a few minutes of stretching, joints move further and resist movement less. But this effect is transient. Once the stretching stops, flexibility returns to pre-stretch levels. And recovery is largely complete within a few minutes of finishing the stretch.
It’s possible, but less certain, that stretching also has long lasting effects on flexibility. Everyday observations suggest that’s true, because ballet dancers and yoga teachers, who stretch a lot, tend to be more flexible than the rest of us. But, while it seems obvious that regular stretching makes people more flexible, it has proved remarkably difficult to demonstrate that in controlled experiments.
Either way, the effects of stretching on flexibility – short or long term – could be exploited to enhance performance of some sports. It seems likely that hurdlers or gymnasts, for instance, could perform better if they were more flexible. i.e. stretching could increase performance in sports that require flexibility.
To stretch or not to stretch?
For recreationally active people, these research findings suggest stretching is unlikely to have much benefit, although it probably won’t do you any harm. If you like stretching, stretch. If you don’t like stretching, don’t do it, but don’t feel guilty about not doing it.
For high-level athletes, stretching might increase performance in sports that require lots of flexibility; it makes more sense to stretch if you’re a hurdler than if you’re a weightlifter.
Similarly, good evidence of the superiority of one method of stretching over another, or of the long-term effects of particular kinds of stretching, doesn’t exist.
To finish on a more positive note: while it appears that stretching doesn’t appreciably reduce risk of injury, there’s good evidence that warming up does. An intensive, well-structured, active warm-up can substantially reduce risk of injury, so try doing that the next time you exercise.
I acknowledge the work ofSenior Principal Research Fellow at Neuroscience Research Australia, in preparing this article.