Exercising is healthy, or, rather: not exercising is unhealthy. Scientists disagree on all sorts of things, but the beneficial effects of exercise on our health are largely undisputed. But how healthy are sports activities? And is it possible to exercise so much it becomes unhealthy? Researchers at the Leyden Academy on Vitality and Aging recently published a study in the authoritative British Medical Journal that sheds a light on these issues.

The main problem is with studies of athletes is, compared to non-athletes, they do not just exercise: they smoke less, drink less, tend to go to bed early and eat differently; consequently you cannot precisely isolate the effects you want to study. The Leiden researchers used a very elegant solution: they only studied Olympic athletes. From a public sports databank, they selected nearly ten thousand people who had taken part in the Games between 1896 and 1936 of whom the date of death was known. Using that group, they compared the different sports to each other. After all, if very intensive exercise were unhealthy, you would expect racing cyclists and marathon runners to die sooner than athletes who play cricket or golf.

On average, Olympic athletes live longer than their fellow-countrymen, according to PhD student Frouke Engelaer. "I think that it does not depend solely on the exercise; if they didn’t exercise, they would still live longer. It’s a very select, super-healthy group. Besides: if they win, they get lots of admiration. And we know, from studies in which Nobel-Prize winners and Oscar winners were compared to nominees who lost, that social status raises your life expectancy."

And when athletes are compared to each other? Athletes who exercised very intensively proved not to live any longer than moderately active athletes. The same conclusion was drawn in a German retrospective published last summer: exercise is healthy, but there is no evidence to suggest that very intensive exercise is better. "‘The more, the better’ does not seem to apply to exercise", Engelaer states succinctly.

But the popular belief is that top athletes, particularly racing cyclists, burn themselves up quickly. Engelaer explains: "There is very little real evidence for that. Obviously, cyclists risk being killed by a fall and that reduces the average life expectancy. But to adjust for that, we only included deaths after fifty."

The most striking discovery in the Leiden paper was that athletes who often sustained knocks were more likely to die prematurely; the scientists estimate that this affects a percentage of between six and twenty per cent of top athletes. "We think that a succession of knocks must resemble an accelerated ageing process. The boxers are the most extreme example: they literally knock each other to dementia. If you accumulate enough damage, after a while it won’t heal and eventually becomes irreconcilable with life. And that is what ageing is, in essence." But Engelaer stresses that this is not limited to boxers: "You only see gymnasts when the routine goes well but to get that far, they will have bumped themselves many times falling off the beam."

Life cut short by as much as twenty per cent, that is quite a bit. And, with all due respect to the pre-war athletes, their modern colleagues exercise considerably more. Everything is faster, the balls hit harder, the opponents you crash into are more muscled and therefore heavier. What should modern athletes expect? Last week, a British research group responded to the BMJ article; they had been studying professional rugby players, who might seem super-human on the outside but medical examination revealed that they were wearing out more rapidly than their fellow humans. It looks as if an early death awaits them too.

"It would be very sensible to launch a large study that follows knocked-about athletes for a long period", suggests Engelaer. "Do they suffer more brain damage? You would expect their kidneys and livers to stop working properly; is that right?" And what if the answer to those questions is "yes"? "That is something that coaching teams will have to consider when they are working with young, potential athletic talent. Fewer heading drills at football practice, for example. It’s worth to discuss with the parents.’