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To stretch, or not to stretch?

In our latest Training article, Jonathan Bean takes an in depth look at stretching – and explores whether or not it is worth doing…

Stretch, stretch, stretch*. As runners we are often told to stretch before and after running. Stretch to warm up, stretch to improve flexibility, stretch to avoid injuries, and stretch to recover quickly. Stretching and running go hand in hand and feels intuitively right to many runners.

The problem is, the scientific evidence suggests that all this stretching could be unnecessary. Not only is it probably not adding any benefit, it may even be harming your running.

The theory goes that to run efficiently, a certain amount of natural elasticity in our muscles is beneficial. Stretching reduces that elasticity, meaning we use more energy. For more detail on this, read on…

(*At this point, for ease of explanation, ‘stretching’ refers to ‘static stretching’. Other kinds of stretching will be explained below).

Where has the ‘stretching is good’ theory come from?

Perceived wisdom would suggest that runners should stretch. After all, runners have always done it (or been told to!).

Many of us were taught that stretching is important in school PE lessons. This advice is then repeated by many personal trainers, coaches, magazine articles and runners themselves. The ability to touch our toes is even included in many fitness tests, which reinforces the message that flexibility is to be desired.

And why not? It seems to make sense:

  • Running makes you feel stiff…
  • Feeling stiff can be uncomfortable…
  • Therefore we need to stretch to counteract the stiffening effects of running.

That’s logical, right?

Possibly not – as we’ll explain below.

The development of a runner’s body

Improvement in running is a matter of stress and adaptation. When we go for a run, we place the body under stress, putting our heart, lungs, muscles, joints and bones (plus other bodily systems) under strain and causing small amounts of damage.

This strain prompts the body to repair that damage and adapt to become better able to withstand the stress we put it under. If we repeat an activity often enough, and allow enough recovery time for the adaptations to occur, then our bodies will gradually become finely tuned to suit that activity.

The more we run, the more our bodies become suited to running.

We readily accept the vast majority of bodily changes to be good things, that will benefit our running. For example; a lower resting heart rate, stronger muscles, more blood vessels to get oxygen where it is needed, etc. Given that all of these other side effects of running are considered beneficial, it is odd that ‘less flexibility’ or ‘stiffer muscles’ is often considered a problem.

If the body changes itself to become better suited to running, then the stiffness we feel should also be considered part of this process. Indeed, the science does suggest this to be the case.

Why is stiffness a good thing? 

It all comes down to efficiency. Stiffness is thought to reduce the amount of energy required to run due to what is known as the ‘stretch-shortening cycle’.

The muscles and tendons in our legs act like springs. As we run, our muscles and tendons become stretched out. Just like a stretched spring they want to return to their starting position. A tight spring will ‘ping’ back to its natural state quicker than a loose spring. The same is true for muscles and tendons.

Different muscles are used at different points of the running cycle, stretching or contracting in turn. This coordinated sequence of stretching and contracting helps pull your legs through the range of movement required. Tighter muscles will naturally contract quicker than loose muscles.

By stretching our muscles to increase flexibility, we reduce their natural elasticity, making them less efficient and thus requiring more energy to move forwards.

The more natural elasticity you have – from having stiff muscles – the less energy you will need to move forwards. Clearly, this would appear to be a good thing.

Sounds plausible. Where’s the evidence?

We’ve shared some links to scientific research below, should you wish to do your own reading on the subject, but here are some key statements:

“The significant relationship [between lack of flexibility and improved running economy] demonstrates that the less flexible distance runners tended to be more economical, possibly as a result of the energy-efficient function of the elastic components in the muscles and tendons during the stretch-shortening cycle.”

TL Trehearn & RJ Buresh, 2009.

“Correlational analyses revealed that […] runners who were less flexible […] were more economical. Although speculative, these results suggest that inflexibility in certain areas of the musculoskeletal system may enhance running economy in sub-elite male runners by increasing storage and return of elastic energy and minimizing the need for muscle-stabilizing activity.”

MW Craib, et al, 1996.

“These results suggest that the least flexible runners are also the most economical. It is possible that stiffer musculotendinous structures reduce the aerobic demand of submaximal running by facilitating a greater elastic energy return during the shortening phase of the stretch-shortening cycle.”

AM Jones, 2002.

All suggest that decreased flexibility results in greater efficiency when running.

What about injury prevention?

The picture is less clear as to whether or not stretching and increased flexibility reduces the risk of injury. This is because there are so many different factors involved when a runner gets injured, that it is hard to isolate precise causes. There are also ethical issues with deliberately injuring runners in a laboratory!

On the one hand, greater flexibility might be seen to reduce the risk of straining a muscle. You can pull a loose elastic band a lot further than a tight one before it snaps. The same may be true of muscles.

On the other hand, reduced flexibility might prevent a muscle being extended to the point where it is damaged. Consider a rolled ankle: Loose ankle muscles, tendons and ligaments might allow the ankle to roll further, but there’s a possibility a more elastic joint might ping back into position before it is over-extended.

Additionally, it has been suggested that over-stretching (to the point where you ‘feel the burn’) will break down some of the muscle or tendon fibres, adding to the damage that is already done by running.

Given the above, it is possible that stretching might help prevent injuries in some cases, but could increase the risk in others. Referring back to the experts, the jury is out:

“There is no scientifically based prescription for flexibility training and no conclusive statements can be made about the relationship of flexibility to athletic injury.”

GW Gleim & MP McHugh, 1997.

But don’t I want a long stride length?

Yes, a lovely, long-legged stride is something to aim for. After all, the further we can extend our legs behind us, the further we can travel with each stride, and the faster we’ll cover the ground.

Look at side-on photos of élite runners in full flight (such as Great Britain international marathoner, Charlotte Purdue, in the Instagram post below) and you’ll see what this looks like. Their hip extension is long, and their ankles are very mobile. Despite their long stride lengths many pros are incapable of touching their toes.

The key here is to understand the difference between flexibility and range of motion. Or, the difference between static and dynamic stretching.

Static stretching is what we’ve been referring to so far in this article. It’s the act of staying in one place and holding a stretch for an extended period of time – whether that’s a few seconds or a few minutes.

Dynamic stretching is what happens when we move. The pendulum effect of our swinging legs causes them to extend to their limit then ping back.

Referring back to the concept of ‘stress and adaptation’ mentioned above, static stretching will result in our bodies becoming very good at stretching statically. That is, they will become more flexible and we’ll find it easier to extend them to their limits and hold the position.

Dynamic stretching, which happens when we run, will prompt our bodies to become better at stretching dynamically. That is, the range of motion will increase and we’ll maintain the elasticity that we want.

To return to the elastic band analogies, static stretching gives us a long elastic band without much springiness. Dynamic stretching gives us a short elastic band that can extend a long way and pings back sharply. It is the latter elastic band that we want.

How do I do dynamic stretching?

Dynamic stretching happens naturally when we run. With each step, we stretch our muscles, but don’t hold that stretch, as they return to their starting position immediately.

When running slowly, with short steps, there isn’t much stretching happening, so the dynamic stretching effect is minimal. Therefore, to increase our range of motion, we  should do movements that emphasise the dynamic stretching effect.

These movements include actions that exaggerate aspects of the running cycle. For example:

  • Short sprints (when we naturally extend our stride);
  • Lunge walking (without holding the position);
  • Skipping with high knees;
  • Leg swings (one leg standing, the other one swinging like a pendulum);
  • Bum kicks (kicking your heels up behind you so they hit your bottom); or
  • Bounding (hopping continually from one foot to the other, trying to get as far as you can with each step).

All these movements will help increase your range of movement and extend your stride length, without causing the muscles to become slack from holding the stretches.

The Instagram post below shows some of the élite women of the NN Running Team doing dynamic stretches:

View this post on Instagram

Let's move! ?

A post shared by NN Running Team (@nnrunningteam) on

Please note, dynamic stretching is not the same as ballistic stretching. Ballistic stretching is like static stretching – as you hold a particular pose – but ‘bounce’ it to get extra strength. It should be avoided as it pushes the muscles and tendons further than they would naturally go, causing damage.

What about my warm up?

Based on the scientific research mentioned above, it seems that static stretching before a run is likely to reduce the natural elasticity you want to run efficiently.

If you’re concerned that you’ll feel too stiff to run without your usual stretching routine, just start off slowly. Many of the fastest runners in the world start their runs either walking or jogging very slowly until their legs feel ready to run.

The dynamic stretches mentioned above are good to do when you have longer to warm up, such as before a race or a hard run. After a few minutes of easy jogging, work through some of the movements. Try not to do so many that you tire yourself out, but do a few to prime your legs for the effort to come. Every runner’s body is different, and may feel different from day to day, so it may take some trial and error to find the right combination for you. 

To keep some spring in your step, especially in the middle of a period of heavy training, pop a few dynamic stretching movements into some of your general, easy runs. A little goes a long way, but a lot can place your joints under extra stress; so think of dynamic stretching exercises as a little extra spice, not the main ingredients for a meal.

Anecdotally, the author of this article has found that a couple of short sprints can be a great way of shaking out tired legs during a long run without resorting to stopping and static stretching.

Is there ever a time for static stretching?

Some studies suggest that static stretching after exercise can prompt a release of the growth hormones our bodies use to aid recovery. This is good, as more growth hormones mean quicker recovery times.

However, this should probably be weighed up against the reduced running efficiency that results from being too flexible. It may be the case that there is a static stretching sweet spot that gives the benefit of added growth hormone without reducing muscle elasticity, but it is unclear where that is.

If your legs tighten up mid-run or during a race, static stretching can offer a sensation of instant relief, but may not be the best option as it can place further strain on muscles that are already under stress. Instead, you may want to:

  • Slow down (to help your body clear the lactate and other by-products that can cause your legs to tire);
  • Eat or drink something salty (as a lack of sodium, from sweating, may be causing an electrolyte imbalance that’s making you cramp up); or
  • Do a couple of short sprints, or slightly faster running (to stretch your muscles dynamically).

If the above don’t work, then consider giving static stretching a go.

My physiotherapist has prescribed static stretching. Are they wrong?

If you are rehabilitating an injury, and your physiotherapist has told you to stretch, then you should probably trust their advice and continue to do so.

As seen above, under ideal circumstances, we want stiffer muscles and reduced flexibility. When injured, however, our body is not in an ideal state, so the normal rules might not apply at that particular moment.

By all means, speak to your physiotherapist if you have a concern, but the chances are they have told you to stretch to correct an imbalance or address some other temporary biomechanical concern that has caused your injury.

In conclusion

Scientific research suggests that, generally speaking, runners should not static stretch. Doing so reduces the elasticity of their tendons and muscles and will reduce running efficiency.

If you are a runner that has previously worried that they don’t stretch enough, then you can now relax, safe in the knowledge that by not stretching you may have been doing the right thing all along.

However, if you’re a runner that has always stretched, then at least you will have just learnt that by stopping your stretching routine, you might just become a more efficient runner – and have more free time!

Regardless of where you stand on static stretching, a good range of motion is helpful as it gives a long stride for faster running. To achieve this, we can either include more fast running in our routine, or mimic some of those movements with dynamic stretches.

Above all, we need to trust in the process of stress and adaptation. If our bodies are responding to running in a certain way, there’s a very good chance those responses are going to help make us more efficient runners. This is as true of decreased flexibility as it is of any other physical adaptation.

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References

Craib, MW, Mitchell, VA, Fields, KB, Cooper, TR, Hopewell, R, & Morgan DW 1996, ‘The association between flexibility and running economy in sub-elite male distance runners’, Medicine & Science in Sports & Exercise, vol. 28, no. 6, pp. 737-43.

Gleim, GW, & McHugh, MP 1997, ‘Flexibility and Its Effect on Sports Injury and Performance’, Sports Medicine, vol. 24, no. 5, pp. 289-99.

Jones, AM 2002, ‘Running economy is negatively related to sit-and-reach test performance in international-standard distance runners’, International Journal of Sports Medicine, vol. 23, no. 1, pp. 40-3.

Trehearn, TL, & Buresh, RJ 2009, ‘Sit-and-reach flexibility and running economy of men and women collegiate distance runners’, The Journal of Strength and Conditioning Research, vol. 23, no. 1, pp. 158-162.

Yamaguchi, T, Takizawa, K, & Shibata, K 2015, ‘Acute Effect of Dynamic Stretching on Endurance Running Performance in Well-Trained Male Runners’, The Journal of Strength and Conditioning Research, vol. 28, no. 11, pp. 3045-52.

Training with Eliud Kipchoge – 5 Things That Surprised Me‘, www.SweatElite.co