Is it possible to exercise too much?

While most people have a hard time getting in enough exercise, at the opposite end of the spectrum are those who do too much.

While not getting enough exercise has all sorts of negative health implications – like weight gain and increased risk of certain diseases – overexercise also has its downsides.

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The most common effects of overexercise are acute injuries—say, a torn anterior cruciate ligament (ACL) or a sprained ankle—and musculo-skeletal overuse injuries. These involve damage to a bone, muscle, ligament, or tendon as a result of repetitive stress without allowing time for the body to heal. Shin splints, Achilles tendon rupture, plantar fasciitis, tennis elbow, and stress fractures are a few examples. Symptoms include pain during or after physical activity and chronic, persistent pain even at rest.

Compulsive exercising can also lead to overheating.

“Heat exhaustion or [heat] stroke may be dangerous, and caution is warranted with intensive, sustained, hot exercise,” says Jack Goodman, a professor in the faculty of kinesiology and physical education at the University of Toronto’s Goldring Centre for High Performance Sport, “but hydration and common sense are often the best counter-measures.”

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Long-term endurance athletes have a greater risk of developing certain arrhythmias, such as atrial fibrillation.

“It’s unwarranted to suggest that overexercising is dangerous to the heart, but it does appear that in certain individuals, a predisposition to the development of arrhythmias exists,” Goodman says.

And while we’ve all heard of someone who has dropped dead during a marathon, Goodman says that in fact, the risk of having a heart attack during intense activity is very low.

“It’s important to emphasize that those who die during exercise from a heart attack have heart disease,” Goodman says. “It’s the stress of exercise that triggers the event, but they must have a disease environment for an adverse outcome to occur.”

“Events like sudden death are in frequent—about one in 200,000 marathoners,” he says. “Ninety-eight per cent [of those people] have evidence of disease.”

So how much exercise is too much?

Well, the jury is out on that one.

Because there are so many variables – a person’s fitness level, the type of activity they’re doing and at what intensity, their age and health history – it’s hard to come up with an exact figure. That said, there are a few rules of thumb.

“There are no upper limits defined by global and consistent experience,” explains Goodman, who’s also adjunct scientist, at the clinical cardiovascular research laboratory. “The term [“overexercise”] evolved because there are studies, many of them from my laboratory, that show that the heart shows fatigue or diminished function after prolonged exercise—like 120 minutes-plus.”

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“’Excessive’ is well beyond the normal, recommended amounts known to reduce risk [of cardiovascular disease] and benefit health,” he says.

Rather than adopt a Madonna-style exercise regime that involves a few hours spent working out every day, follow the national recommendations such as those issued by the Canadian Society for Exercise Physiology. Adults should get at least 150 minutes of moderate to vigorous physical activity every week.

Moderate-intensity physical activity—like brisk walking and bike riding— is defined as anything that causes adults to sweat a bit and breathe harder. Vigorous activities make people sweat and become out of breath – think jogging and cross-country skiing.

Increases in weekly training time, mileage, or strengthening repetitions should be no more than 10 per cent per week. For example, if you’re 10 kilometres this week, increase to 11 next week.

If you’re training for a marathon, Goodman suggests following reliable resources such as Runner’s World. Consider an approach that involves a hard day of exercise followed by an easy one. And remember that rest is a good thing.

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“The overarching key is slow, steady, and very gradual progression,” Goodman says. “Listen to your body; your body needs rest, and a rest day is fine as it won’t take away from your fitness even at the higher end of competitive goals.”

And even though overexercise isn’t healthy, don’t use that as an excuse to sit on the couch.

“It’s far more unsafe not to exercise at all,” Goodman says.

What do you think of these findings? Are you guilty of overexercise? Let us know by tweeting to @YahooStyleCA.