More Exercise Isn't Always Good For You

The 2014 City To Surf race in Sydney. Brendon Thorne/Getty Images

Contrary to popular belief, more exercise is not always better.

Doctors know that regular physical activity, such as brisk walking and jogging, helps the management and rehabilitation of cardiovascular diseases and lowers the risk of death from hypertension, stroke and type 2 diabetes.

The Physical Activity Guidelines for Americans recommends about 150 minutes a week of moderate exercise or about 75 minutes of vigorous exercise.

But there is clear evidence of an increase in cardiovascular deaths in heart attack survivors who exercise to excess, according to a new study published in Mayo Clinic Proceedings.

Paul T. Williams, of the Life Sciences Division, Lawrence Berkeley National Laboratory, and Paul D. Thompson, of the Department of Cardiology, Hartford Hospital, studied the relationship between exercise and cardiovascular disease-related deaths in about 2,400 physically active heart attack survivors.

Remarkable reductions in deaths from cardiovascular events of up to 65% were seen among patients who were running less than 30 miles (48 kms) or walking less than 46 miles (74 kms) per week.

Beyond this point however much of the benefit of exercise was lost, in what is described as a reverse J-curve pattern.

“These analyses provide what is to our knowledge the first data in humans demonstrating a statistically significant increase in cardiovascular risk with the highest levels of exercise,” say Williams and Thompson.

“Results suggest that the benefits of running or walking do not accrue indefinitely and that above some level, perhaps 30 miles per week of running, there is a significant increase in risk. Competitive running events also appear to increase the risk of an acute event.”

However, they point out that “our study population consisted of heart attack survivors and so the findings cannot be readily generalized to the entire population of heavy exercisers”.

A weekly cumulative dose of vigorous exercise of not more than about five hours has been identified in several studies to be the safe upper range for long-term cardiovascular health and life expectancy.

It may also be beneficial to take one or two days a week off from vigorous exercise, and to refrain from high-intensity exercise on an everyday basis.

See the video for an explanation of how to exercise for longevity or peak performance:

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