Answer : A Miriam E. Nelson, PhD, director of Tufts John Hancock Center on Physical Activity, Nutrition, and Obesity and vice-chair of the committee for the US governments first-ever Physical Activity Guidelines for Americans in 2008, replies: First, the American Heart Associations guidelines for physical activity are out of date. The national recommendations are for:
- 150 minutes per week of moderate activity OR
- 75 minutes per week of vigorous activity
- Or some equivalent combination of the two.
I think this is important as it provides more flexibility for Americans to meet the guidelines. Also, this amount is the base level to promote health; greater improvements in health will come with more activity.
As for intensity, the best way to measure intensity is by perceived exertion using the talk test. If you can carry on a conversation without any challenge, it is usually classified as low intensity. If you can carry on a conversation, but need to stop speaking here or there, then it is moderate; if you can only talk in short sentences, then it is vigorous.