Does running really wreck your knees?

You’ll wreck your knees - will you?

You can see the logic. For every stride a runner takes, pounding the pavement, it is the poor old knees soaking up the impact, destroying that cartilage, bit by bit, until he or she is a dead cert for arthritis. Yet the evidence actually shows the reverse may be true.

A study of nearly 75,000 runners and nearly 15,000 walkers published in 2013 found that runners were significantly less likely to develop arthritis than the walkers – the risk was actually roughly half. Paul Williams, the author of the study, suggested that running lowers BMI more than walking, and that lower body weight is the key to preventing arthritis. Further, his study showed that the greater the weekly mileage of the runner, the lower their risk rate dropped. Again, this could be related to a lower body weight: the single-largest risk factor for knee osteoarthritis is obesity.

There is, he concludes , “no evidence that running increases the risk of osteoarthritis, including participation in marathons.”

Of course, if you have a family history of, or susceptibility to, arthritis, then this is not to suggest that taking up running is a good idea. As a study published last year in the British Journal of Sports Medicine says: “Much remains unknown and the running research base to inform clinical decision-making is thin” – this applies particularly to those who already have a diagnosis of joint pain or osteoarthritis.

What remains likely, however, is that for those in general good health, and with no risk factors, the benefits of running would outweigh any potential risk to the joints.

Stretching is vital - is it?

Popular wisdom has it that if you don’t stretch before, or after – or both – every run, you’ll be susceptible to injuries, not recover as quickly and be hobbling painfully for days. Not necessarily so.

A review by the Cochrane research network looked into the effects of stretching on muscle soreness and found consistent results across 12 relevant, randomised controlled studies.

Eleven, admittedly, were pretty small (10-30 people), while one was very large (2,337 people, around half in the “stretching” v control groups). But while some of the studies were of better quality than others, the consistent results were the same: that stretching had little or no effect in reducing soreness.

So what about injury prevention?

There is precious little evidence here, too – though the issue is also very hard to study, as the variables are so great. Most studies look simply at groups who stretch, groups who don’t, and then count the injuries in each. It’s not the best method but, for what it’s worth, it shows no correlation between stretching and injury prevention.

A review in the Clinical Journal of Sports Medicine concluded that “the basic scientific literature supports the epidemiological evidence that stretching before exercise does not reduce the risk of injury”. In another review , the same author concluded: “Studies suggesting that stretching before exercise is not beneficial should be weighted as stronger.”

There is even some suggestion that stretching (particularly of the static kind) could be actively bad for you, though this seems to apply more to sprinters than endurance runners. What is now universally agreed, however, is that functional movement is more important than static stretching. If you really want to stretch before running, make it “active” rather than static. Or just start at a really, really easy pace.

Heel-striking bad, midfoot good, barefoot is best. Really?

For many years, the vogue in recreational running has been to be as “natural” as possible. The theory goes that you are less likely to be injured if you run in the way that “nature intended” – though nature presumably didn’t intend concrete, tarmac, broken glass, sedentary lifestyles and expensive running shoes.

The problem is that much of the impetus for this idea – aside from Christopher McDougall's Born to Run book , about the literally barefoot Tarahumara Native Americans in Mexico – comes from the observation that elite athletes don't heel strike, that is, landing on the heel first, but instead run on the forefoot. There are several problems here.

First, sometimes they do heel strike and, second, when they don’t, it’s largely a result of the simple mechanics of running that fast. Try sprinting and heel striking at the same time: it just isn’t physically possible. However, if you run at a less godlike pace – as 99.9 per cent of us do – it may actually be more efficient to heel strike: researchers at the University of Massachusetts demonstrated in a computer-simulated study that at a 7:36-minute-a-mile pace, heel striking was approximately 6 per cent more efficient than mid or forefoot striking. Other research suggests that the “threshold” where the economy levels out between mid and heel strikers is 6:25 mile pace.

A study from 2012 of 52 athletes at a US college did show that the forefoot strikers had fewer injuries than heel strikers, but this proved little – the numbers are too small, the variables are too many. More to the point, these runners were “natural” forefoot strikers, not those who had chosen to make a deliberate change to their style.

This, really, is the point for most runners: if it ain’t broke, don’t fix it. Forums online are full of people asking how they can “transition” to a more “natural” style, then claiming (anecdotal) evidence of how brilliant it is. The reality is that the transition involves starting again from scratch: a process that would fix most injuries, regardless of what style you start running in.

Guardian service