We’ve all heard the litany of health benefits associated with keeping your body in shape. In case you thought a good workout was climbing three flights of stairs twice daily, think again. This week, the Department of Health & Human Services weighed in on how much exercise is enough. And for most adults, it’s two-and-a-half hours a week of “moderate intensity physical activity, such as brisk walking.” Or you could substitute an hour and 15 minutes a week of “vigorous” aerobic (endurance) exercise. Think jogging or running.

WORK OUT! New federal guidelines suggest the minimum exercise adults should undertake each week.

Unless you get obsessive about it, cardiovascular and other health benefits will increase with increasing workouts. How much does of an increase is HHS talking about? Roughly double their recommended minimum — i.e. five hours a week of moderate or two-and-a-half hours a week of vigorous exercise.

And vary the workouts. At least twice a week tackle muscle-strengthening (resistance) workouts “that are moderate or high intensity and involve al major muscle groups.”

Although any activity is better than none, most benefits trace to fairly frequent, high intensity, and prolonged bouts of endurance and resistance exercise. In general, exercise benefits tend to “far outweigh the possibility of adverse outcomes.” (You think they’re talking about a sprain  — or heart attack?)

Even the elderly and disabled individuals can benefit from exercise. But the motto for beginners at any age: Start slow and go slow. Increase activity as the body adapts to using muscles in new or exaggerated ways.
For those who doubt any gains are worth the pains, take a look at a 2007 study by a U.S.-Canadian team of researchers. It found that exercise kept the muscle in older adults looking younger  — even on a cellular and genetic level. And that’s important because one of the more debilitating aspects of aging is the inexorable loss of muscle (which inevitably gets replaced with fat), known as sarcopenia.

Janet Raloff

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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