Washington: Contrary to the popular belief, more exercise is not always better as too much running could lead to an increase in cardiovascular deaths in heart attack survivors, a new study has claimed.
There is strong epidemiological evidence of the importance of regular physical activity, such as brisk walking and jogging, in the management and rehabilitation of cardiovascular disease and in lowering the risk of death from other diseases such as hypertension, stroke, and type 2 diabetes, researchers said.
However, there is clear evidence of an increase in cardiovascular deaths in heart attack survivors who exercise to excess, according to the study published in Mayo Clinic Proceedings.
Researchers at the Department of Cardiology, Hartford Hospital in US, studied the relationship between exercise and cardiovascular disease-related deaths in about 2,400 physically active heart attack survivors.
The study confirmed previous reports indicating that the cardiovascular benefits for walking and running were equivalent, as long as the energy expenditures were the same.
Remarkable dose-dependent reductions in deaths from cardiovascular events of up to 65 per cent were seen among patients who were running less than 30 miles or walking less than 46 miles 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," said researchers.
"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," they said.
However, they point out that "our study population consisted of heart attack survivors and so the findings cannot be readily generalised to the entire population of heavy exercisers."