Contrary to what you might think, people who work out for hours aren’t more likely to suffer from overtraining. (Photo: efecreata mediagroup / Shutterstock)

Debunked: extreme exercise isn’t harmful

Are hours of daily exercise unhealthy? No, says researchers behind a new report.

The world’s first marathon runner Phidippedes ran from the city of Marathon to Athens carrying news of the Greek victory over the invading Persian forces.

When he'd covered the long distance of 40.5 kilometer, poor Phidippedes succumbed to exhaustion and died soon after.

You would think that’d be enough to deter anyone from attempting to accomplish the same feat -- but it’s not, and you probably know a bunch of people who willingly jump into their runners and cover a 42.195 kilometer marathon or perhaps even a triathlon of a whopping 225.9 kilometers.

Seemingly these people have no fear of suffering the same fate as Phidippedes -- but should they?

Extreme exercisers:

Spend many hours on workouts (more than 6 hours of running each week or more than 10 hours of biking each week.

Hard training: they push themselves to the limit.

Exercises every day or almost every day.

Almost 10 per cent of the men and 5 per cent of the women spend more than 10 hours on exercise every week.

Especially young people aged 16 to 19 spend many hours on exercise.

No, is the conclusion of a new report from the Danish Council for Health and Disease Prevention. People who exercise for more than 10 hours a week aren’t running a higher risk of hurting themselves, shows the report.

“There are some risks but generally there’s nothing harmful in extreme exercise,” says co-author Kristian Overgaard from the Department of Public Health, Aarhus University. “Of course you still need to pay attention to your body’s signals, that’s the key conclusion.”

Mortality remains unchanged

Five per cent of the Danish population can be labelled as ’extreme exercisers’, according to the report, The authors wanted to know if there was anything special about this segment who works out a little more than usual.

One conclusion was that mortality rates did not increase more than usual compared to the normal population. It’s been proven on more than one occasion that exercise has a positive effect on life expectancy.

“There’s no basis in the literature to say extreme exercisers risk dying younger,” says Overgaard. “But we don’t know what happens if you continue past your prime.” Exercise doesn’t automatically mean a free pass to a long life, he adds; there’s still the risk of illness and diseases.

Overgaard is backed up by Professor Michael Kjær, director of the Institute of Sports Medicine Copenhagen, Bispebjerg Hospital. Inactivity is more dangerous than overtraining, he says.

“To put it bluntly: there’s only one thing that’s dangerous and that’s not to exercise,” says Kjær. “There are many more risks involved with being inactive.”

Sudden deaths often caused by hidden illness

Even though mortality rates aren’t affected by training hard there are still many cases of people who suffered sudden deaths after long periods of training.

Overgaard says such sudden deaths are rare and not necessarily connected to physical activity.

“When young people suddenly die while practising sports it’s often caused by a hidden heart disease,” he says. “It’s not automatically the amount of training that causes the death.”

In Italy, everyone practising sports on an elite level are screened for hidden diseases. Overgaard thinks that’s a problematic practice because you risk making otherwise healthy people fear they’re sick.

Other than risk of sudden heart failure, the new report also looks at:

  • Biochemical changes
  • Sports injuries
  • Overtraining
  • Immune system and infections

And extreme exercisers are no different from the normal population as long as they pay attention to their body's warning signals, the report concludes.

Exercise can become an obsession

The new report doesn’t only deal with the physical aspects of extreme exercise – in one chapter Ph.D. Mia Beck Lichtenstein looks at exercise addiction: when people become obsessed with their training.

She says that workout sessions can end up taking up so much of people's lives that they won’t have time for anything or anyone else. If they are kept from their workout they’ll even experience withdrawal symptoms similar to those of alcoholics.

“There’s a huge focus on those who exercise too little but really we need to know more about those who exercise too much,” says Lichtenstein who’s a post doc at the Institute of Psychology at University of Southern Denmark.

“Exercise will never make you immortal”

So don’t be afraid of completing a marathon or even an iron man. But try and keep it there, says Kjær.

“A marathon is near the limit of what’s physically possible,” he says. “But while your traning to get ready your health benefits greatly.”

People who’ve kept exercising throughout their entire life will experience that the body’s health remains at a high level, he says.

But even so, you can’t use exercise as an escape for everything, says Overgaard.

“Your risk of heart disease remains the same even if you increase the workout load,” he says. “You can’t exercise your way to immortality.”


Read the full story in Danish on

Translated by: Kristian Secher

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