Endurance performance: the anatomy of a perfect warm up

What’s the very best way to warm up for maximum endurance performance? In this 2-part article, Andrew Hamilton looks at what the scientific research says

Unlike mechanical engines, the human body is not ideally designed to suddenly work hard when in a rested state. It will do it of course – our ancient ancestors would often have had to suddenly sprint away from a potential predator – but at a cost to performance potential and the possible risk of injury. When you’re running/riding/swimming hard, you can be burning anything from 10 to 20 times more energy than you use at rest and without some kind of preparation for this intense work, your body will be put under quite a bit of physiological stress.

For starters, muscles that are cold are also more inelastic, increasing the amount of internal friction (and effort) required for muscle movement. Cold muscles also lack an optimum flow of oxygenated blood, which leads to higher concentrations of muscle-fatiguing lactate if you work them hard without first warming them up. Not only that, but the joints involved in the running/pedaling/swimming action (ankles, knees hips, shoulders etc) are stiffer and require more effort to move through their natural range of movement when they’re cold making the ligaments supporting these cold joints more prone to damage or tears. So, if you simply tear off up the road or leap into the pool without any warm up, it’ll not only feel far more tiring, you’ll also be increasing your injury risk into the bargain.

Moving the warm-up goalposts

Once upon a time, all the sport science and PE textbooks were unanimously agreed on what constituted the perfect pre-exercise warm up:

• A gentle to moderate aerobic pulse raiser to send oxygenated blood (and extra heat) to the working muscles;
• Mobilisation work to loosen the joints;
• Some pre-exercise stretches to prepare the muscles for the larger range and velocities of movements they would encounter during exercise.

This kind of warm-up approach was universally endorsed and why wouldn’t it be? It was based on sound physiological principles and it all seemed very logical. However, a very big problem began to emerge – a succession of scientific studies into optimum warm-up protocols showed that this traditional approach is left wanting in some areas and may even result in worse performance than no warm up at all!

Pre-exercise stretching in a warm up

Let’s go in reverse order and look at pre-exercise stretching first. There are basically three types of stretching that may be recommended as part of a warm up: static, ballistic and dynamic (see panel 1). One of the UK’s leading researchers in this area is Dr Gary O’Donovan who specialises in the relationship between exercise, health and performance. In a comprehensive review article, Dr O’Donovan analysed the  findings from a number of scientific studies on pre-exercise stretching⁽¹⁾. In 61 studies investigating the acute effects of static stretching on strength and power, the conclusions on performance were as follows:

• *One study found an improvement in performance;
• *Thirty-eight studies found reductions in performance;
• *Twenty-two studies found no statistically significant differences in performance between stretching and non-stretching groups.

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Panel 1: Types of stretching

• Static stretching involves the passive elongation of a muscle or group of muscles by stretching and holding statically. Static stretching is often use in rehabilitation programmes but in the past has also been recommended as part of a pre-exercise warm up.
• Ballistic stretching involves swinging, bouncing or bobbing movements but the main difference is that the final (fully extended) position is not held.
• Dynamic stretching is different in that it represents ‘flexibility in action’ Examples include ankle flicks, buttock flicks, knee lifts, the ‘Russian walk’, the ‘walking lunge’ and the ‘walking hamstring’.

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The results also showed that as little as two 15-second stretches were sufficient to reduce performance and more demanding stretching protocols reduced performance for up to two hours following stretching! Hardly surprising then that Dr O’Donovan concluded that ‘pre-exercise static stretching is a waste of time or, worse, is detrimental to performance’!

Next under the microscope was pre-exercise ballistic stretching and there wasn’t much to cheer about here either. In the six available studies reviewed, there were no reports of improved performance (one report of decreased performance and five inconclusive reports) suggesting there’s simply not enough evidence to support the use of ballistic stretching in a warm up.

Finally, Dr O’Donovan turned his attention to dynamic stretching. Out of ten studies, six found improvements in performance, while three other studies found no statistically significant differences in performance between stretching and non-stretching groups. The tenth concluded that dynamic stretching was beneficial, but unfortunately the authors compared changes in performance in the dynamic stretching and static stretching groups instead of the dynamic stretching and non-stretching groups, which makes the findings unreliable. Overall, the available evidence suggests that dynamic stretching in a warm-up is beneficial. What is less clear however is how much of this benefit comes from the heat created (ie the warming up and increased blood flow) and how much from the actual stretching component!

The inescapable conclusion then is that any warm up should only include dynamic type stretching and even then, the benefits may arise mainly from the ‘warming up’ that dynamic movements create rather than from the stretching component. Ballistic stretching appears to be a waste of time while static stretching is more likely to be harmful than beneficial to your cycling performance!

Can warm up stretching reduce injury?

If stretching as part of a warm up doesn’t boost performance, can it help prevent injury? The prevailing wisdom is that it can but once again, the actual evidence is very weak. One study of 2,377 adults concluded that “stretching probably reduces the risks of some injuries”⁽²⁾. However, the quality of this study was very poor: participants were recruited over the Internet and never even met the investigators; adherence to the stretching intervention was not objectively measured and seemed to be low; injuries were reported online and it turns out that the injury rates were actually not significantly different between the stretching and non-stretching groups.

Reliable cause-and-effect relationships (eg does stretching produce fewer injuries) can only be properly investigated in randomised, controlled trials (RCTs). There are two outstanding RCTs about the effects of stretching before exercise on the risk of injury: a study of 1,093⁽³⁾ and a study of 1,539⁽⁴⁾ recruits to the Australian army. Both of these studies found that stretching before exercise did not reduce the risk of injury during 12 weeks of intensive training and until solid evidence appears to the contrary, there’s no reason to believe otherwise!

The actual warm up

So far, we've looked at the (rather dubious) evidence for the benefits of including stretching in a warm up and concluded that only the use of dynamic stretches is supported by science. But what of the actual warming up process itself? How should it be put together? That's what we'll consider in detail in the second and final part of this article.

References

1. Sports Performance Bulletin; 2010, volume 290, p9-11
2. Br J Sports Med. 2009 89:p1016-1026
3. Aust J Physiother. 1998;44(3):165-172
4. Med Sci Sports Exerc. 2000;32(2):271-277