The Stretching Debate: What does the evidence say?

There’s been a bit of a backlash against stretching within the fitness industry over the last few years – some even going as far as to say that stretching is bad for you and you shouldn’t do it.  A lot of this opinion is loosely based on recent research regarding stretching prior to exercise and injury prevention, but is it actually bad for you? Or does it actually prevent injury like your  under 13’s footy coach told you?

Well the short answer  is no…… and yes….. (you’ll see what I mean a little later)

Back in the day, you would go to footy or netball training and your warm-up would be two laps around the oval and 10 minutes of static stretching before you start training or playing.  (Static stretching being where you sit, lie or stand and hold stretches for 20-30 seconds each). This was to make sure you “warmed up properly” and “don’t hurt yourself.”  There is a lot of research now to show that this type of static stretching prior to exercise does not reduce your injury risk, including several big systematic reviews (a high level of scientific evidence) that all show that static stretching as part of warm up does not reduce you risk of injury.

So does this mean that stretching is bad for you? Well no, no it doesn’t.  If we look at the evidence it found that there was no difference in the risk of injury between the stretching groups and the non-stretching groups. This means that stretching as part of warm up does not increase your risk of injury either. Some people in the fitness industry have taken this research and declared that stretching is bad for you, but looking at this evidence we know that actually it’s not.  Having said that – based on the evidence we wouldn’t recommend static stretching as part of your warm up normally.

But wait, there’s more!

Static Stretching has also been shown to reduce peak power and force output in the muscle stretched.  This is often referred to as  acute stretch-induced strength loss. What this means is that after static stretching, your muscle is not able to produce quite as much force (strength) as it could prior to stretching. As we know that reduced strength is a risk factor for soft tissue injury, again some proponents are up in arms against stretching. Also when playing sport why would we want to reduce our power output? It would only impair performance.

In reality this effect has been shown to only last for a few minutes, so whether this is likely to increase your risk of injury really depends on when you stretch and what you are doing afterwards.  If you are an Olympic weightlifter, it would not be wise to perform heavy static stretching within say 15 or 30 minutes of competing or performing maximal lifts.  Not necessarily because it will increase your risk of injury, but because it could reduce your performance somewhat (and the numbers quoted are often between 2% and 7% reduced strength – not exactly severe weakness). Interestingly, studies show that while peak power output is reduced immediately after stretching, a long term program of stretching does not reduce strength or power overall (provided you don’t test it immediately after stretching). So stretching yesterday will have no impact on your strength or power today.

So when we think back to those days of footy training, that warm up protocol really doesn’t assist in warming us up, and doesn’t reduce injury risk.  Therefore, the current best practice recommendation for warm up prior to exercise would be to NOT perform static stretches, but instead perform dynamic warm up designed to prepare your body for the exercise to come.  This should include things like large amplitude, controlled dynamic movements (such as leg swings), activities to gradually increase blood flow to the areas needed for exercise and activation/preparatory movements relevant to the activity. For example if you are playing basketball and likely to be doing a lot of jumping, warming up should probably include some loaded leg activities such as squats and lunges.  Maybe even practice some light jumping and landing before you hit the court and jump as hard as you can. If you’re a baseball pitcher – you probably should perform specific shoulder warm up.  As with everything in life – preparation is key.

The other issue with this “old school” warm up is that when you stay still and perform static stretching after your two laps around the oval, you are actually cooling down. After raising your core temperature and increasing blood flow to the muscles and areas we need it to exercise by jogging, we are then doing the opposite by sitting down and stretching. So again, no to static stretching as part of warm up. (Do you see a theme here?)

So does this mean we should never stretch for warm up?

Well no, not always. I always say if you have something that you feel needs stretching before you exercise (like that old dodgy hamstring) and it makes you feel better (or more prepared to exercise) to stretch it – then by all means stretch it.  As we know, research shows it doesn’t really increase your risk of injury either. But make sure you include mostly active/dynamic warm up as well, and don’t do it immediately before really heavy deadlifts.

So what about injury prevention?

Now we also know from the research that a lack of mobility can be a risk factor for injury (depending on what you are doing).  A long distance runner, for example, only moves through a limited range of movement in specific directions. So their requirement for mobility/flexibility is less. An Olympic gymnast has very high requirements for mobility/flexibility – so they would need much higher levels of mobility to be considered not at risk.

Stretching at other times (NOT during warm up) does have some evidence to support a reduction in muscle and tendon injury risk.  There is also evidence to suggest that stretching after exercises can reduce the severity of muscle soreness.

In the real world, however, it should all come down to what your problem is and what you are trying to change. (We would call this specificity and it’s one of the most important considerations when designing rehabilitation, treatment and conditioning/training programs):

If you have impaired mobility/flexibility, and the sports/work tasks you perform require greater levels of mobility – then you should perform flexibility training to improve.  The same way that if you want to get better at running, you need to train running.  If you want to get stronger – you need to do strength training.  If you want to be more flexible/have better mobility – you need to do mobility training.

In clinical practice – if your lack of flexibility or mobility is assessed and deemed to be contributing to your problems – then we would provide you with specific intervention to address this.

Now static stretching is just one type of mobility intervention.  Other popular types include PNF stretching (so hot right now), where we use muscle contraction and relaxation to affect muscle lengthening, joint mobilization, ballistic stretches (not always recommended) and even recently a study has been published showing that self myofascial release (foam roller, spiky ball etc) is effective in improving mobility/flexibility.

*A quick note on feeling the need to stretch:  Muscles that feel “tight” are not always the ones that need stretching.  Short muscles usually require flexibility training.  Tight muscles are often weak muscles or overworked muscles (if we ignore post-exercise soreness). Persistently stretching them may lead to increased fatigue (due to reduced peak power output) and lead to more “tightness” feelings. Strengthening “tight” muscles is often a very effective intervention to relieve that persistent tension feeling.  Every week I see someone who “carries too much tension in their shoulders – and they stretch and stretch and it just won’t loosen up”.  This is an excellent example of muscles that are likely overworked or lack endurance. Stretching is not likely to provide any long term resolution for this problem.

Modern concepts in stretching

There have been recent advances in our understand of how stretching and flexibility works.  Traditionally we would think of our muscles like a rubber band that could be loosened or stretched with mechanical stretching.  We now know that the nervous system controls our flexibility much more than we thought.  Part of the limits of our flexibility is how much our nerves “put the brakes on” to protect our tissues from damage by excessive length or tension.  This is part of our “danger” mechanism.  There are receptors in our muscle spindles (muscle cells) and golgi tendon organs (stretch receptors in our tendons) that provide feedback to the nervous system and constantly drive a certain amount of tension that resists excessive length in the muscles.  Remember your muscles do not do anything by themselves – they need the brain and the nerves to tell them what to do.  When people are under general anaesthetic (and their neural drive is turned right down) – suddenly they have excellent flexibility! Stretching is now thought to inhibit that neural drive, or modulate the “danger” response.  Passive stretching also seems to reduce peak power output because it inhibits the neural drive to the muscles.

Nerve tissue itself is also sensitive to excessive tension, and will drive muscle contraction/tension to protect it from excessive tension.  This means that “muscles protect nerves”.  With this in mind, we can also affect limited mobility and pain by modifying neurodynamics. Mobility or neural desensitization treatments/exercises can also improve mobility and reduce pain/tightness.  You know that tightness you feel in your calves or behind your knees when you touch your toes – that’s neurodynamic restriction in action!

Take Home Messages

1. Static stretching prior to exercises does not reduce your risk of injury. Therefore performing these stretches as part of your warm up is not recommended.  Perform a dynamic warm up that adequately prepares your body for the task at hand.
2. However, flexibility and mobility training is actually very good for you – if you have a restriction in flexibility. It can reduce post exercise soreness and reduce injury risk if you do not have the requisite flexibility to perform the required movements of our sport, or it is contributing to your symptoms. Perform targeted, specific flexibility training if you want to improve your flexibility.
3. Tight feeling muscles may not need stretching.  Short muscles may need to improve flexibility, but tight muscles may be overworked, fatigue or weak. This particularly goes for postural muscles.
4. The nervous system appears to be the primary driving force behind flexibility (or lack of).  The nervous system protects the body from injury/danger by resisting excessive muscle length.  Stretching can desensitize this protection mechanism, and teaches the nervous system that this new length is comfortable and not dangerous.
5. Neurodynamic treatments and mobilizations can have a profound effect on your mobility and symptoms.

Hopefully this has enlightened you in ways to make a  difference to your life and to help you understand why your body works the way it does.  If you are having any issues with mobility, function or pain we are always here to help. Please feel free to get in contact with us with any queries regarding this or anything else.  We are always happy to hear from you.

Julian Bowen

Julian is a Director and Senior Physiotherapist at Parmelia Physiotherapy.  He has spent  over a decade working exclusively in private physiotherapy practice, and estimates he would have performed over 35,000 individual treatments in that time. He has worked with everyone from Paralympians,  elite athletes, WAFL Footballers, the Defence Forces and weekend warriors, to thousands of everyday people with all manner of issues.  He is passionate about injury prevention and has a special interest in the treatment of headaches, shoulder issues, hypermobility management and exercise rehabilitation for the prevention and treatment of injuries. 

 References:

1. Small, et al. (2008). A systematic review into the efficacy of static stretching as part of a warm-up for the prevention of exercise-related injury.Research in Sports Medicine, 16(3), 213-231.
2. Lauersen, et al. (2014). The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials. British Journal of Sports Medicine, 48(11), 871-877
3. Konrad & Tilp, (2014). Increased range of motion after static stretching is not due to changes in muscle and tendon structures. Clinical Biomechanics, 29(6), 636-642
4. Schroeder et al., (2015) Is self myofascial release an effective pre-exercise and recovery strategy? A literature review.
    Curr Sport Med Rep 14,  200-208
5. McHugh & Cosgrave, (2010). To stretch or not to stretch: the role of stretching in injury prevention and performance. Scandinavian Journal of Medicine & Science in Sports, 20(2), 169-181.
6. Amako M, Oda T, Masuoka K, et al. (2003) Effect of static stretching on prevention of injuries for military recruits. Mil Med. ;168:442-446