Stretching – helpful or harmful?


For years, right from when we were kids starting sport, stretching has been something that’s been ingrained into us; our coaches told us to do it, our physios & doctors told us to do it, our sporting heroes told us to do it – even Big Merv tried to show us the way!

If we get injured, we often think it was because we mustn’t have stretched enough – researchers recently did a big series of interviews with recreational runners, and ‘not stretching enough’ was the number one thing runners thought caused any of their running injuries1.

 

But is simply ‘stretch more’ really the answer? As we know more and more about stretching; how it works and what it does, our recommendations are changing…..

 

First things first – what does stretching actually do? We know it improves muscle length, but we’re not fully sure how – we used to think that stretching worked by pulling apart bands of collagen that made up our connective tissue, and changed the intrinsic make-up of our muscle fibres, but more recent research suggests that increased length might be more due to changes in nerve function and how our nerves perceive the ‘threat’ of being stretched2, 3.

So, stretching causes us to be more flexible – which if you’re a gymnast or professional contortionist, is essential. But if we think about what happens when we run, we don’t really go into extreme positions all that often….. in fact, we actually want and need a bit of stiffness when running2, 4-6.

 

Think of your legs like a slinky: a slinky that’s super stiff doesn’t bend or move, but a really loose, floppy slinky doesn’t spring back – it just stays in its bent position. We obviously want our legs to bend and move when we run, but also want them to store energy and work like springs – because the more energy that the ‘springs’ can provide to move us forward, the less active muscle work we need to use2, 4. For runners, there may be an optimal amount of stiffness – with some stiffness being better able to transfer elastic energy, and also being beneficial to running economy2, 4-6.

 

The key question though: does stretching prevent injury?

Well, er…no.

 

There’s been a number of big systematic review studies on stretching, with these studies consistently finding no reduction in injury risk as a result of stretching7-11.

Systematic reviews are big compilation studies – the researchers try to find every available study on a certain topic, and see what the consensus is from all of the studies; sometimes one individual study may not show much, but if you look at all of them, you start to see themes emerging.     Because of their size, and that they are evaluating each individual study, they carry a bit more weight in research. Take for instance the review done by Lauersen et al.7 – they looked at all randomised controlled trials of studies looking at injury prevention strategies, which meant that they could analyse data from 26,610 athletes in total; almost 5,000 of whom took part in stretching trials. That’s a huge amount – and certainly much more believable than the results from a small study on a group of 10 runners, say!

  • For the stats nerds among us, the risk of injury in the athletes who stretched was almost exactly the same [Relative risk 0.96 (95% CI 0.85-1.1)] compared to those who didn’t stretch7.

 

In fact, stretching immediately BEFORE you go for a run might actually be a harmful thing. The reason for this is that a muscle can’t produce as much force immediately after it has been stretched – the stretch tends to acutely inhibit muscle activity and force generation3, 12, 13. Indeed, by reducing the muscle’s force generation and therefore reducing its ability to resist stretch, that may be one of the ways by which stretching improves flexibility3, 13. However, when it comes to running, we want our leg muscles producing as much force as they can to help us run faster and prevent injury.

It sounds as if it’s all doom & gloom for stretching – but that’s not the case!

Stretching can still be very helpful, particularly in someone who’s doing a lot of training and prone to muscle tightness, as there’s an ongoing time battle between your muscles recovering from your previous workout, and doing your next one! Stretching is also something that we still use all the time to address specific biomechanical issues and treat a whole bunch of conditions, and it would be wrong to think that muscle tightness isn’t a problem – for example, tight calf muscles may affect your foot mechanics when running, and tight hip flexors (which are very common in those who sit all day for work!) can inhibit how your hamstrings and glutes function14-17.

However, it’s of more benefit to stretch AFTER your run and in-between times, to help your muscles recover from the work that you give them, rather than before you run. Moreover, improving your flexibility is something that takes time and repetition12, 13 – a quick stretch before exercise is not the difference between being ‘loose’ and being ‘tight’.

In summary, stretching can still be very helpful for runners, but it’s of more benefit to do it after your run and in-between times, rather than as a warm-up before you run. A simple light warm-up, such as a walk, slow jog, or some running drills before you start your run, will be much more effective.

 

Reference:
  1. Saragiotto, et al. (2014). What do recreational runners think about their risk factors for running injuries? A descriptive study of their beliefs and opinions. Journal of Orthopaedic & Sports Physical Therapy, 44(10), 733-738.
  2. Dicharry, (2012). Anatomy for Runners. New York: Skyhorse Publishing.
  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. Barnes, et al. (2014). Lower-body determinants of running economy in male and female distance runners. Journal of Strength & Conditioning Research, 28(5), 1289-1297.
  5. Lohman III, et al. (2011). A comparison of the spatiotemporal parameters, kinematics, and biomechanics between shod, unshod, and minimally supported running as compared to walking. Physical Therapy in Sport, 12(4), 151-163.
  6. Ronnestad & Mujika, (2014). Optimizing strength training for running and cycling endurance performance: a review. Scandinavian Journal of Medicine & Science in Sports, 24(4), 603-612.
  7. 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.
  8. Yeung, et al. (2011). Interventions for preventing lower limb soft-tissue running injuries. Cochrane Database of Systematic Reviews, Issue 7. Art. No.: CD001256
  9. Herbert & Gabriel, (2002). Effects of stretching before and after exercising on muscle soreness and risk of injury: systematic review. BMJ, 325(7362), 468.
  10. Thacker, et al. (2004). The impact of stretching on sports injury risk: a systematic review of the literature. Medicine & Science in Sports & Exercise, 36(3), 371-378.
  11. 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.
  12. Page, (2002). Current concepts in muscle stretching for exercise and rehabilitation. International Journal of Sports Physical Therapy, 7(1), 109-119.
  13. 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.
  14. Gallo, et al. (2012). Common leg injuries of long-distance runners: anatomical and biomechanical approach. Sports Health, 4(6), 485-495.
  15. Franz, et al. (2009). Changes in the coordination of hip and pelvis kinematics with mode of locomotion. Gait & Posture, 29(3), 494-498.
  16. Chumanov, et al. (2007). The effect of speed and influence of individual muscles on hamstring mechanics during the swing phase of sprinting. Journal of Biomechanics, 40(16), 3555-3562.
  17. Schache, et al. (1999). The co-ordinated movement of the lumbo-pelvic-hip complex during running: a literature review. Gait & Posture, 10(1), 30-47.