Could jogging be bad for you?

French President Nicolas Sarkozy is recovering after collapsing while jogging. So what are the health hazards?
Mr Sarkozy collapsed on Sunday after 45 minutes of "intense physical activity" in hot weather in Versailles.

The president, on a strict new diet and exercise regime, did not lose consciousness but needed to lie down, said officials, contradicting earlier reports that he had fainted.

It had been reported that he had suffered vasovagal syncope - a nerve condition in which exhaustion and dehydration can lead to a loss of consciousness due to a loss of blood pressure. But it seems he actually suffered a vasovagal episode, which is less intense.

A cardiologist at the Georges Pompidou Hospital in Paris was reported as saying that such episodes were caused by a fall in arterial pressure and heartbeat frequency, therefore slowing the blood flow to the head.

So what are the health hazards associated with jogging?

The benefits far outweigh the risks, says Andy Dixon, editor of Runner's World magazine, and it's very rare to hear about the kind of vasovagal episode experienced by Mr Sarkozy.

"It seems to have been triggered by a combination of the exertion of running, the strict diet he was on and dehydration from the heat," he says.

Two ways to prevent this would be to hydrate your body while running - but not too much - and warm down properly afterwards so that the heart rate, blood supply and the muscles can return to normal.

"The current advice is to drink only when you feel thirsty, because the body acts like a sophisticated sensory device and you'll get a dry mouth and feel dehydrated when you need to drink.

"And at the end of a run, rather than just stopping dead, it's better to run a bit more slowly and slow down until walking fast, allowing the body to adjust gradually back to rest."

A more common complaint among runners than fainting is the impact on joints, says Mr Dixon, although the risks should not be exaggerated.

"It's a high-impact activity but the more you do it, the stronger your joints get. There's a fallacy that it wrecks your knees and ankles but there's a long-term study that says the more you do it, it ends up strengthening them."

source: bbcnews.com