The evidence is clear that regular exercise has many health benefits. It decreases the risk of heart attacks, strokes, Type 2 diabetes, osteoporosis and many forms of cancer. It lowers weight and blood pressure, helps with sleep, and relieves stress and depression. People who exercise live longer and have better quality of life as they age.
Most authorities recommend moderate-intensity aerobic exercise such as brisk walking (4 miles per hour) for at least 30 minutes a day, but only a minority of Americans achieve this. Additional benefit occurs with 60 minutes a day and even more with 90 minutes. I tell patients to walk at least 30 minutes a day, fast enough so that they could talk but not sing. People age 40 and older need to also do strength training (e.g. resistance bands, light weights, kettlebell) for 20 minutes twice a week on non-consecutive days. The reason for this is that loss of strength starts at around 40, which contributes to aging. If you exercise but sit at a desk the rest of the day, that undoes the benefit of exercise, so use a standup desk and/or walk around every 30 minutes.
Beyond about 90 minutes a day of moderate exercise or lesser amounts of intense exercise, the risks may outweigh the benefits, and in this valley we definitely see overexercisers. (Full disclosure: I include myself in this group.) These people have convinced themselves that if some exercise is good, more must be better, and are either addicted to exercise (the endorphin high) or are competitive enough that they push themselves beyond what is health-promoting.
How to define too much exercise varies with the exerciser, but as a Supreme Court justice once said about obscenity, “I know it when I see it.”
Prolonged/intense exercise has been shown to cause elevation of cardiac enzymes such as troponin, indicating damage to cardiac muscle. This kind of exercise can also result in small scars, that can interfere with the heart’s electrical conduction system.
An excellent book on this subject, published earlier this year, is “The Haywire Heart, how too much exercise can kill you, and what you can do to protect your heart.” The authors are John Mandrola, M.D., a cardiac electrophysiologist (a cardiologist who subspecializes in problems of the electrical conduction system of the heart); Chris Case, editor of VeloNews; and Lennard Zinn who custom makes bicycles in Boulder. All three are elite athletes, and Zinn has a personal history of a heart arrhythmia that…