Stretching the Truth
It’s a given that stretching makes you more flexible. We’re also told that stretching reduces the risk of injury. However, this relationship isn’t clear cut at all.
It’s difficult to isolate the relationship between stretching and injury when conducting research. There are many factors that relate to injury risk. Fitness, strength, and previous injury for example are important factors. Most of the research investigating stretching and injuries has followed groups of athletes or military recruits. Using military recruits in stretching studies has its advantages. Military recruits are reasonably homogenous. Factors such as age, exercise, and diet are similar in groups of recruits. When recruits are divided into a group that stretches and a group that doesn’t stretch, we’re comparing “stretching” apples with “non-stretching” apples. However, using these results from young males in military studies to prescribe stretches for your female 65-year-old client may be a stretch.
One of the larger military studies (following 900 recruits over two years) show less back injuries occur with a stretching programme. Military studies also show that the most flexible and the least flexible male recruits had increased injury risk. Recruits with low flexibility tended to suffer from overuse injuries while flexible recruits were more likely to suffer from acute injuries. This suggests that we need a certain amount of flexibility for the tasks we’re given – but too much or too little may predispose us to injury.
An Australian military study with more than 1500 recruits in basic training compared training with a warm up, with a warm up and the addition of six lower body stretches held for 20 seconds. There was no difference injury rates between the groups after 12 weeks of training. Fitness measured by a 20m shuttle test was a better predictor of injury leading the researchers to suggest that fitness training rather than flexibility training may be a better investment of your time if you’re looking to reduce your injury risk.
A meta-analysis in 2014 also suggested that factors other than flexibility may be more important for reducing injury. This study assessed over 3500 different injuries in over 26000 subjects. Stretching had no effect on these injuries while proprioceptive training and strength training halved the risk of injury.
It appears once you have sufficient flexibility, fitness training and strength- and body awareness-training may be more protective than stretching.
Some studies have also reported increased injury rates with stretching. In theory sustained stretches of 90s may compromise muscle function for up to 2 hours afterwards. In practice though, not many people will hold a stretch for over 90s. In reviews of stretching and performance we see around a 50/50 split, with static stretching showing a detrimental effect on performance or no effect at all. Bottom line here is that long sustained stretches prior to activity probably aren’t useful for performance and may even be detrimental. If you’re going to use static stretching – stretching after exercise or well before you start exercising is best practice. Dynamic flexibility work makes more sense prior to exercise. Reviews on dynamic stretching show a 50/50 split with improved performance or no effect in performance – a better bet for your time spent prior to exercise. Here’s a video of my daughter Ella going through some dynamic stretches prior to a cross country run.
So – should we stretch to reduce the risk of injury?
While there isn’t much evidence that stretching reduces the risk of injury, I wouldn’t tell someone not to stretch after exercise. Once you’ve got adequate range of motion for your activity investing your time in fitness, strength, and proprioception work seems to be a better investment for injury prevention.