18/04/2016 5:18 PM AEST | Updated 15/07/2016 12:51 PM AEST

How Much Exercise Is Too Much?

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young fitness woman runner running at seaside

There are no regrets that follow a sweaty workout session.

The benefits are endless -- improved mood, more energy -- plus, the pride of starting (or ending) your day active as opposed to scrolling Instagram in bed is pretty priceless.

But is there such a thing as too much exercise?

“For the general population certainly up to one to two hours a day is going to reduce your risk of all-cause mortality, that is dying -- however, there are obvious risks associated with overtraining,” Professor Tim Olds, School of Health Sciences, University of South Australia told The Huffington Post Australia.

Injury being the most apparent, Olds explains there is also a transient increase in the risk of a heart attack during exercise, compared to if you were say, sitting in front of the TV. That said, exercise will reduce the risk of heart attack -- and death -- overall.

“It's a bit like a vaccination: you could have a bad reaction when you get it, but in the long run, so to speak, it will protect you.”

“However, the fact that the risk is transiently increased does mean that in principle, really extreme exercise may do more harm than good,” Olds said.

So what constitutes too much? Well, that’s where it gets tricky.

One of the problems with knowing whether extreme exercise causes problems is that very few people in the population do large amounts of vigorous exercise.

"Most epidemiological studies show that risk of death decreases with vigorous exercise of up to about one-and-a-half to two hours per day, but don't say much about exercise beyond that,” Olds said.​

There have been some recent studies however, suggesting that very high levels of exercise may be associated with negative outcomes.

A US study found that while exercise in general prolonged life in heart attack​ survivors, those who jogged more than 7.1 kilometres per day or walked more than 10.1 kilometres per day were likely to die earlier.

For healthy people, a Danish study looked at 4000 joggers and non-joggers. The lowest death rate was found for people who jogged one to two-and-a-half hours per week (about 10-20 minutes per day) at a slow-average pace.

The current guidelines for adults recommend 150 to 300 minutes of exercise a week, roughly 30 to 60 minutes a day, five days a week.

“Of course, you do get that group of really fanatical exercisers, but we really don’t know the long term health implications for them,” Olds said.

While there is no question there is added pressure on the body if you’re exercising more than two hours a day, Olds said the main concern is when people are endurance training in the heat, which is when you can lose a lot of fluid, resulting in blood becoming thicker and a risk of a stroke is increased.

The takeaway? Stick to exercising no longer than two hours each day and, at the very least as per the current guidelines, 150 to 300 minutes each week.