How Much Physical Activity is Enough?
Physical inactivity is a major public health problem. There is compelling evidence that an active and fit way of life has many health benefits, and being sedentary is a contributing factor in several chronic diseases and conditions. Increased physical activity is associated with improvements in numerous health conditions, including coronary artery disease, hypertension, stroke, insulin sensitivity, osteoporosis, and depression. But how much activity is necessary to help us maintain a healthy lifestyle?
The current public health recommendations from the Department of Health and Human Services for physical activity are for 30 minutes of moderate-intensity activity per day for adults. Moderate activity is described as walking 3-4 miles per hour or undergoing exercise in the 40-70% maximal functional capacity. The 2008 Physical Activity for Americans guidelines suggests 150 minutes (two hours and 30 minutes) a week of moderate intensity physical activity, such as brisk walking. The guidelines also encourage aerobic (endurance) and muscle-strengthening (resistance) physical activity. They clearly state that the health benefits of physical activity far outweigh the possibility of adverse outcomes. They report that adults should perform aerobic activities in episodes of at least 10 minutes or longer to 30 minutes per episode spread throughout the week. They suggest doing muscle-strengthening activities that are moderate or high intensity and involve all major muscle groups on two or more days a week. These activities should involve resistance training of at least 60% of what they can maximally lift to enlist strength gains.
Older adults should attempt to perform 150 minutes of exercise per week, but when unable, they should be as physically active as their disabilities and conditions allow.
The guidelines for safe physical activity are as follows:
- Understand the risks of exercise but be confident that physical activity is safe for almost everyone.
- Choose types of physical activities that are appropriate for their current fitness level and health goals; some activities are safer than others.
- Increase physical activity over time whenever more activity is necessary to meet health goals. Inactive people should “start low and go slow” by gradually increasing how often and how long activities are to be done.
- Protect themselves by using appropriate gear and sports equipment, looking for safe environments, following rules and policies, and making sensible choices about when, where and how to be active.
- Be under the care of a health-care provider if they have chronic conditions or symptoms. People with chronic conditions and symptoms should consult their health-care provider about the types and amounts of activity appropriate for them.
There has been a surge in popularity of a step counter called a pedometer that is a small device that is worn at the hip that counts the number of steps walked per day. It has been recognized that a specific recommendation guideline of taking 10,000 steps per day did produce significant clinically relevant reductions in weight and blood pressure. Several studies have found that using a pedometer increased about 2000 steps or about one mile of walking per day. The research also found that setting a step goal and using a diary might be key motivational factors for increasing physical activity. Tudor-Locke proposed the following indices be used to classify pedometer-determined physical activity in healthy adults:
| <5000 steps/day | sedentary lifestyle index |
| 5000-7499 steps/day | typical of daily activity excluding sports/exercise as low active index |
| 7500-9999 steps/day | includes some added activities – somewhat active index |
| >10,000 steps/day | active index |
| >12,000 steps/day | highly active index |
References:
Blair SN, Kohl HW, Gordon NF. How much physical activity is good for health? Annu Rev Publ Health 13: 99-126, 1992.
Blair SN, LaMonte MJ, Nichaman MZ. The evolution of physical activity recommendations: how much is enough? American J Clin Nutrition 79(5): 913S-920S, May 2004.
Ryan CG, Grant PM, Tigbe WW, Granat MH. The validity and reliability of a novel activity monitor as a measure of walking. British J Sports Med 40(9): 779-784, September, 2006.
Bravata DM, Smith-Spangler C, Sundarum V et al. Using pedometers to increase physical activity and improve health. JAMA 298(19): 2296-2304, November, 2007.
Tudor-Locke C, Bassett DR Jr. How many steps/day are enough? Preliminary pedometer indices for public health. Sports Med 34(1): 1-8, 2004.
Berlin JE, Storti KL, Brach JS. Using activity monitors to measure physical activity in free-living conditions. Physical Therapy 86(8): 1137-1145, August, 2006.
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