The Physical Activity Guidelines for Americans were released Tuesday by the U.S. Department of Health and Human Services.

In addition to 2.5 hours a week of moderate physical activity, or one hour and 15 minutes of vigorous physical activity a week such as water aerobics or ballroom dancing, adults should incorporate muscle strengthening activities, such as weight training, push-ups, sit-ups, or heavy gardening, at least two days a week, the guidelines say.

If a chronic condition prohibits an older adult's ability to follow these guidelines, they should be as physically active as their abilities and conditions allow under the guidance of a healthcare provider.

Children should have one hour or more of moderate or vigorous aerobic physical activity a day, including vigorous intensity physical activity at least three days a week. Children and adolescents should incorporate muscle-strengthening activities, such as rope climbing or sit-ups, three days a week.

Moderate intensity aerobic activities include hiking, skateboarding, bicycle riding and brisk walking, while vigorous aerobic activities include running or sports such as soccer, basketball and ice or field hockey.