10 February 2013

An attempt to run a marathon using SCIENCE: part V (Stretching)

Tut tut. Two weeks without an update. It's becoming apparent that if there's one time of the week that I'm least inclined to blog, it's on a Sunday evening after the most demanding run of the week. But I'm persevering, even after today's 30k - in appalling conditions - into which I mixed some nasty hills, just for "fun".

So this week I've been researching stretching. Personally, I've never been much of a stretcher. But since starting training with my local athletics club, I've adopted some of the dynamic stretching exercises we use at the track for my own running routine. More about those later though. Let's start with more basic static stretches. These are the kind that you can do standing or sitting on the spot. If you watched the Australian Open final the other week, you will have seen the frighteningly flexible Novak Djokovic running through a series of static stretches during one of the breaks between games. Whether these were meant to aid his tennis performance or just to intimidate his opponent, I've no idea. We're focusing on running.

The theory behind pre-run stretching was always that it would reduce muscle soreness and the risk of injury. As most serious runners will probably know, however, experts are now advising against static stretching before running. This is backed up by some fairly extensive studies on static stretching vs no stretching. In 2002, the British Medical Journal published a review of studies on stretching before and after exercise that suggested the benefts of pre- and post-exercise stretching for muscle soreness and injury prevention were at best tiny.
"...on average, about 100 people stretch for 12 weeks to prevent one injury and (if the hazard reduction was constant) the average subject would need to stretch for 23 years to prevent one injury."
And 23 years is a really long time to have to hold a stretch... sorry.

At the time, the review authors concluded that there was not enough evidence to say whether stretching could improve performance. But more recently, in 2009, US reviewers found an "acute bout" of stretching before exercise could actually impair muscle strength. With regard to injuries, they said there was no evidence for reducing overuse injuries but some, limited evidence for reducing muscle strain. Yet another review, published by The Cochrane Collaboration in 2011, found stretching - before or after exercise - did not reduce later muscle soreness.

None of these reviews were specific to running. But a year later, an orthopedic surgeon (and lifelong runner) called Dan Pereles was involved in a stretching study that recruited 2729 runners via the USA Track and Field website. I found this particular study interesting because it tells us something about why this type of research is difficult to carry out, and why the practice of stretching persists, despite its lack of any real benefit.

Like many studies before it, Pereles' study split the runners into two groups: a stretch group and non-stretch group. Runners fell injured at exactly the same rate over a three month period - 16% or just under 1 in 6 of the volunteers - whichever group they were in. So again, no discernible benefit of stretching for injury prevention. But what's interesting is that many of the runners who initially volunteered to be involved backed out as soon as they found out they would not be able to stretch for three months. And therein lies the problem: runners are creatures of habit. They can become so attached to their routines that they are afraid of changing them, even when there is little indication that these routines are doing them any good. The fact that it took two years to get enough runners to balance out the stretch and non-stretch groups is telling.

Having said that, many of those runners who backed out probably saved themselves an injury, because as it turned out, those who were avid stretchers and ended up having to join the non-stretching group were more likely to injure themselves (almost 1 in 4). Why? It seems no one is exactly sure, but it may have had something to do with an abrupt change in a routine that the body has already adapted to. The lesson: if you're going to change your routine, do it slowly and carefully. I guess we could also conclude from this study that stretching is nothing but a harmless waste of time. So if you're married to your routine, perhaps there's no real harm in sticking to it.


All of this doesn't necessarily mean that stretching is pointless. Some static stretches are targeted at specific muscle groups and connective tissues and may help in prevention of or rehabilitation from injury - at times other than before a run. There also seems to be some confusion about whether static stretching might be of benefit when it's part of a more general warm up. And in some forms of exercise, like ballet, stretching may be more beneficial for helping athletes (or dancers) achieve the range of movement they need. I haven't looked into other sports, so it's worth seeking out more detailed research, if it exists.

What of my dynamic stretching then? This is basically movement-based stretching or drills a bit like you might see footballlers doing as part of their warm up. I like to refer to it as the Ministry of Silly Walks. It's the kind of stretching that's really quite embarrassing to do on the side of the road at 7am, especially when you live opposite a bus stop. Plenty of coaches are subscribers to the dynamic stretching approach - including Robert Chapman, who coaches elite distance runners from Team Indiana Elite. He says:
"...by engaging in these activities, we can neurologically activate specific muscle groups prior to running, which helps us minimize injuries and perform better in the subsequent workout."
Sounds a bit hand wavy and to be honest, I haven't been able to track down many references for dynamic stretching, despite plenty of pages on the internet recommending it based on miscellaneous "research". However, that 2009 review I mentioned refers to various potential benefits, including raising core temperature ahead of exercise and increasing your range of motion without damaging your performance during the exercise. This recent study found that male sprinters performed better after 1-2 sets of dynamic stretches, but less well after 3 (suggesting too much dynamic stretching could be tiring). On the other hand, dynamic stretches seemed to have little effect on long distance running performance.

So I guess that brings me back to the central question of whether dynamic stretching is really going to help me in my marathon running efforts. I wonder whether its use might actually be limited to the shorter track sessions. But hey, I'm a creature of habit - why change now? After all, it doesn't seem to be doing me any harm...

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