Move more, sit less and get kids active as young as age three, say new US federal guidelines that stress that any amount and any type of exercise helps health.
The advice is the first update since the government's physical activity guidelines came out a decade ago. Since then, the list of benefits of exercise has grown, and there's more evidence to back things that were of unknown value before, such as short, high-intense workouts and taking the stairs instead of an elevator.
"Doing something is better than doing nothing, and doing more is better than doing something," said Dr. Donald Lloyd-Jones, a preventive medicine expert at Northwestern University in Chicago.
Only 20 per cent of Americans get enough exercise now, and the childhood obesity problem has prompted the push to aim younger to prevent poor health later in life.
The biggest change: Start young.
Guidelines used to begin at age 6, but the new ones say preschoolers ages 3 through 5 should be encouraged to take part in active play throughout the day. They don't call for a certain amount but say a reasonable target may be three hours of various intensities.
From ages 6 through 17, at least an hour of moderate-to-vigorous activity throughout the day is recommended. Most of it should be aerobic, the kind that gets the heart rate up such as brisk walking, biking or running.
At least three times a week, exercise should be vigorous and include muscle- and bone-strengthening activities like climbing on playground equipment or playing sports.
For adults, the duration stays the same - at least 2 to 5 hours of moderate-intensity plus at least two days that include muscle-strengthening exercise like pushups or lifting weights.
One key change: It used to be thought that aerobic activity had to be done for at least 10 minutes.
Now even short times are known to help. Even a single episode of activity gives short-term benefits such as lowering blood pressure, reducing anxiety and improving sleep.
Sitting a lot is especially harmful.
