August 13, 2014
Sometimes More Exercise Is Not Always Better, Especially For Heart Attack Survivors
April Flowers for redOrbit.com - Your Universe Online
Exercise is good for the body and mind. Many studies have shown that moderate, regular exercise, such as brisk walking or jogging, can help with weight loss, mood changes, the management and rehabilitation of cardiovascular disease, and even lowering the risk of death from diseases such as hypertension, stroke and Type 2 diabetes. Currently, the Physical Activity Guidelines for Americans suggests 150 minutes a week of moderate-intensity, or 75 minutes of high-intensity exercise to maintain optimum health. But is there such a thing as too much exercise?According to a new study, published in the Mayo Clinic Proceedings, the answer is yes. The findings indicate a clear link between cardiovascular deaths in heart attack survivors who exercise to excess.
The research team, comprised of Paul T. Williams, PhD, of the Life Sciences Division, Lawrence Berkeley National Laboratory and Paul D. Thompson, MD, of the Department of Cardiology, Hartford Hospital, analyzed the association between exercise and cardiovascular disease-related deaths. Using the National Walkers' and Runners' Health Studies databases, the researchers conducted a prospective long-term study with about 2,400 physically active heart attack survivors. The National Walkers' and Runners' study confirmed prior results which demonstrated walking and running gave the same cardiovascular benefits, as long as the energy expenditures were the same. For example, running takes half as long to expend the same number of calories as walking.
Patients who ran less than 30 miles or walked less than 46 miles a week saw a remarkable 65 percent dose-dependent reduction in death from cardiovascular events. Much of the benefit was lost past this point, in what scientists call 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," the researchers said in an Elsevier Health Sciences statement. "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 caution, however, that "our study population consisted of heart attack survivors and so the findings cannot be readily generalized to the entire population of heavy exercisers."
Another study in the same issue of the Mayo Clinic Proceedings describes a meta-analysis of ten cohort studies aimed at providing an accurate overview of mortality in elite athletes. Over 42,000 top athletes, participating in football, baseball, track and field, cycling were examined, including Olympic level athletes and Tour de France participants. Of the total cohort, 707 athletes were women.
"What we found on the evidence available was that elite athletes (mostly men) live longer than the general population, which suggests that the beneficial health effects of exercise, particularly in decreasing cardiovascular disease and cancer risk, are not necessarily confined to moderate doses," comments Alejandro Lucia, MD, PhD, of the European University Madrid, Spain. "More research is needed however, using more homogeneous cohorts and a more proportional representation of both sexes."
"Extrapolation of the data from the current Williams and Thompson study to the general population would suggest that approximately one out of twenty people is overdoing exercise," commented James H. O'Keefe, MD, from the Mid America Heart Institute in Kansas City, MO, and first author of an editorial entitled "Exercising for Health and Longevity versus Peak Performance: Different Regimens for Different Goals," which appears in the same issue. O'Keefe and his colleagues explain that "we have suggested the term 'cardiac overuse injury' for this increasingly common consequence of the 'more exercise is better' strategy." Of those same 20 people, the authors note that 10 are not getting the minimum recommended 150 minutes a week of physical activity.
O'Keefe and his co-authors, Carl "Chip" Lavie, MD, and Barry Franklin, PhD, caution that a cumulative dose of not more than five hours of vigorous exercise is the upper limit identified in several studies for long-term cardiovascular health and life expectancy. They also suggest taking one to two days a week off from vigorous exercise over all, and to refrain from a high-intensity workout on an everyday basis. Instead, the researchers suggest that people from either end of the exercise spectrum—over-exercisers and sedentary people alike—might reap more long-term health benefits by changing their physical activity levels to be in the moderate range.
"For patients with heart disease, almost all should be exercising, and generally most should be exercising 30-40 minutes most days, but from a health stand-point, there is no reason to exercise much longer than that and especially not more than 60 minutes on most days," says Lavie, who is a cardiologist at the John Ochsner Heart and Vascular Institute, New Orleans, LA. "As Hippocrates said more than 2,000 years ago, 'if we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health.' I and my co-authors believe this assessment continues to provide wise guidance," he concluded.