The advice comes amid rising health problems stemming from sedentary lifestyles and obesity among Americans, as well as people in many other nations.
"I think physical inactivity is the biggest public health problem we face. I think it actually accounts for more morbidity and mortality than anything except maybe cigarette smoking," said Steven Blair of the University of South Carolina, one of the experts who crafted the recommendations.
The 1995 recommendations, issued by the American College of Sports Medicine with the Centers for Disease Control and Prevention, had stated, "Every U.S. adult should accumulate 30 minutes or more of moderate-intensity physical activity on most, preferably all, days of the week."
The new guidelines call for healthy adults to engage in moderate-intensity aerobic physical activity for at least 30 minutes five days each week, or vigorous-intensity aerobic exercise for at least 20 minutes three days a week. The guidelines also state that exercise above the recommended minimum amounts provides even greater health benefits.
Moderate-intensity aerobic activity can be a brisk walk, light jogging or other exercise that noticeably accelerates the heart rate. Vigorous-intensity exercise like jogging causes rapid breathing and a substantial increase in heart rate.
The guidelines called for weightlifting exercise to work on muscular strength and endurance, with eight to 10 different exercises on two nonconsecutive days a week.
The new guidelines offered specific advice for people 65 and older, urging them to consider lifting weights, improving their strength to prevent falls, and working on flexibility exercises and balance training.
"If you want to stay out of the nursing home, probably the best approach is to be sure you're physically active and fit," Blair said.
Ailments linked to physical inactivity include cardiovascular disease, stroke, high blood pressure, diabetes, osteoporosis, obesity, colon cancer and breast cancer.
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