All Together Now: 30 Minutes a Day, Five Days a Week

· 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.