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Am Fam Physician. 2008;77(4):513

Background: Inadequate physical activity continues to be related to poorer disease outcomes and is associated, in prospective observational studies, with obesity, cardiovascular disease, type 2 diabetes, and breast and colon cancers. The American College of Sports Medicine (ACSM) and the American Heart Association convened an expert panel to review research and other recommendations published since the original report from the Centers for Disease Control and Prevention and ACSM in 1995.

Recommendations: The recommendations apply to healthy adults between 18 and 65 years of age and those for whom chronic conditions do not impair their abilities to exercise. The recommendations clarify the amount and types of aerobic activity needed to promote and maintain health and to reduce the risk of chronic disease. The guidelines explicitly recommend weight and resistance training to promote musculoskeletal health. Combinations of moderate and vigorous activities can be used to achieve the requirements. The accompanying table lists the components of the recommendations.

To determine the value of each activity, the authors suggest calculating the activity dose, which is determined by the intensity, duration, and frequency of the activity, and using assigned values called metabolic equivalents (METs) that reflect the energy expenditure for a given activity. For example, sitting quietly represents one MET, whereas jogging at six miles per hour represents 10 METs. Multiplying the MET value by the activity duration (in minutes) results in a total (in MET.min). Healthy adults should expend between 450 and 750 MET.min per week to achieve the recommended minimum.

Moderate-intensity aerobic activity (e.g., brisk walking) for 30 minutes or longer at least five times per week, or vigorous-intensity aerobic activity (e.g., jogging) for 20 minutes or longer at least three days per week
Moderate and vigorous-intensity activity is complementary
Combinations of different activities can produce health benefits
Shorter bouts of activity (for at least 10 minutes) may contribute to daily total
Use METs to calculate the total activity value
A comprehensive list of MET values are available at
Healthy adults should expend from 450 to 750 MET.min per week
Resistance or weight training using the major muscle groups is recommended at least two times per week on nonconsecutive days
These activities are in addition to the routine activities of daily living
There is a dose-response effect: exceeding the minimum requirements further reduces the risk of inactivity-related chronic illness

Conclusion: At least one half of American adults are not getting adequate physical activity, which contributes to increasing rates of obesity, morbidity, and mortality from many chronic diseases. These recommendations explain the minimum requirements needed to maintain health. Emerging research suggests that even greater health improvements may result from increasing the amount of physical activity.

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