If you have arthritis, a history of bone fractures, or back or knee problems, high-impact moves may not be safe for you. Check with your doctor or a physical therapist for more specific exercise instructions.
Old think Work at a low intensity (walking at a comfortable pace or sticking to the moderate-level heart rate zone while on a cardio machine). Why? Some women still believe last century’s theory that you drop pounds faster if you work out at a moderate, rather than intense, level.
New think The surgeon general recommends that you fit in at least two and a half hours per week of moderate-intensity physical activity, or at least one hour 15 minutes per week of vigorous-intensity activity—or some combination of both. Many experts suggest you opt for the more intense exercise prescription. “Working out harder challenges the cardiorespiratory system more, and greater cardio fitness is linked to an increased likelihood of living longer,” says Glenn Gaesser, PhD, director of the Healthy Lifestyles Research Center at Arizona State University, in Mesa. Plus, higher intensities may burn off more belly fat.
Important to note: The idea that you’ll lose more weight if you work out at lower heart rates has been debunked. At lower intensities, a higher percentage of fat is burned, but fewer calories overall are consumed. When you work out at higher intensities, you run through more calories in the same amount of time.
The workout updated With high-intensity aerobic exercise, aim to bring your heart rate up to about 95 percent of your maximum heart rate (which is estimated to be around 220 minus your age). The pace should leave you out of breath but not gasping. “At a moderate intensity you can carry on a conversation, but at a high intensity you won’t be able to talk much,” Gaesser explains.
Any type of cardio, such as walking, running, biking or working out on an elliptical trainer, can be performed at a moderate or vigorous intensity, depending upon the effort involved. To boost intensity you can, for instance, move faster, go up hills or crank up an exercise machine’s resistance. Interval programs, which alternate between short bursts of high-intensity exercise and longer bouts of moderate-intensity exercise, are a good way to raise the difficulty level without completely wearing yourself out. “Even sedentary, older or overweight people can work harder if they allow for recovery time by doing higher intensity intervals 30 seconds to one or two minutes a time, followed by slower intervals for several minutes,” Gaesser says. As you develop stamina, shorten your recovery intervals and lengthen your high-intensity intervals.
One caveat: “Your risk of orthopedic or cardiac injury does increase with greater intensity,” says Tim Church, MD, PhD, coauthor of Move Yourself: The Cooper Clinic Medical Director’s Guide to All the Healing Benefits of Exercise (Even a Little!). “So check with your doctor to get the OK to do vigorous exercise, especially if you have medical conditions such as heart disease or diabetes.”
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