New guidelines attempt to clarify a host of issues concerning the proper amount of exercise for certain age groups.

Yes, exercise, but how much?

The federal government released a new set of exercise guidelines a couple of weeks ago, and the basic recommendation was straightforward: Thirty minutes a day, five days a week, at a moderate effort, for basic health; double that and/or make it more intense for more significant health and fitness benefits.

But what if you're over 65? Should you be doing the same things, or approach exercise a bit differently? What about kids — do their developing bodies need a different sort of workout? What if you're pregnant? Or hobbled by arthritis? The new guidelines attempt to clarify a host of issues like these.

Exercise recommendations have been issued over the years by different federal agencies as well as by such organizations as the American Heart Association and the American College of Sports Medicine. While the "2008 Physical Activity Guidelines for Americans" from the Department of Health and Human Services are generally consistent with those recommendations, the attempt here was to provide the broadest possible review of the available science, and to create a document that would have the weight of federal policy.

According to William E. Kraus, a professor of medicine at Duke University's medical school and a member of the advisory panel that assembled the guidelines, that policy dimension gives this document some extra significance: Its conclusions may figure into legislative and other debates about funding for school physical education programs, regulations for the operations of senior-citizens programs and other public-policy questions.

"These guidelines provide muscle that was not available" in the discussion of where physical activity fits in an array of issues, Kraus said. "It becomes part of national policy. ... By doing such a broad review of the science, we feel very confident that HHS is armed with the best data to come up with broad recommendations."

It also takes a sometimes confusing subject and renders it in pretty simple terms.

The effect of a more intense workout, for example, was given a specific multiplier — namely, 2. So if you are willing to work out at a level where you are breathing so hard that conversation becomes difficult, you can cut the recommended times in half — to 15 minutes a day for general health, or 30 minutes a day for more substantial health and fitness improvements. (Don't try to start out at this level, by the way; work up to it.)

The concept of "accumulation" was endorsed, at least as a way to get started. If you have been inactive or have trouble finding a free half-hour, you can still benefit from multiple 10-minute chunks — a walk or calisthenics before work, a stroll at lunch and a final session at night, for example.

For the general adult population, there are more details and suggestions, and forms for tracking daily activity, at

The panel — helpfully, I think — also singled out specific populations for which exercise might seem less important or be more likely to go overlooked. The overriding point was that the general recommendation of five-day-a-week aerobic training and at least biweekly strength training holds for nearly everyone, including senior citizens, women through pregnancy and the postpartum period, and people with chronic problems such as osteoarthritis that might make them overly cautious.

But there are a few specific recommendations and caveats:

  • If people over 65 can't meet the full recommendations, then even small efforts will, over time, improve strength, stamina and coordination. For those who have been inactive or feel at risk of falling, balance training three times a week is recommended, including exercises such as walking backward, heel-and-toe walking and disciplines like tai chi.
  • Pregnant women who have been exercising have no reason to stop, though those accustomed to particularly vigorous workouts may have to adjust intensity in consultation with their doctor. Those who have been inactive before becoming pregnant will benefit from moderate aerobic activity, with little or no risk. Some common-sense exceptions include potential-impact sports like horseback riding, skiing, soccer and basketball; also, after the first trimester pregnant women should avoid exercises that involve lying on the back.
  • People with disabilities from stroke, cerebral palsy, muscular dystrophy or other conditions "should engage in regular activity according to their abilities and should avoid inactivity." Consult with a doctor or therapist about how to adapt exercises or activity to the particular condition.
  • For people with chronic illnesses — the report singles out osteoarthritis, Type 2 diabetes and cancer — regular physical activity can lessen the impact of the disease, improving longevity for some types of cancers, improving mobility and lessening pain for arthritis sufferers, and lowering the risk of heart and other problems associated with Type 2 diabetes.
  • Kids need to be moving at least an hour a day, in ways appropriate to their age. There needn't be so much structure, but there does need to be variety, with activities that are aerobic, build muscle, and help develop balance and coordination. Twenty push-ups, in other words, may be less important than climbing a tree or wrestling a sibling; a jog around the neighborhood may be fine for the parents, but let the kids stick to hopscotch or soccer.

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