Physical activity: how much is enough?

Regular physical activity is an important component of a healthy lifestyle. It offers protection against coronary heart disease (CHD), adult-onset diabetes, hypertension, certain cancers, osteoporosis, and depression (American College of Sports Medicine and U.S. Centers for Disease Control and Prevention, 1993). The American Heart Association now includes physical inactivity as a major risk factor for CHD (1994). Despite the recognized benefits of regular physical activity, only 22 percent of the adult population in this country engages in light to moderate physical activity for at least 30 minutes per day; approximately 25 percent of the adult population is sedentary (U.S. Department of Health and Human Services [DHHS], 1996).

Why are so few people physically active? One possible reason may be that high-intensity exercise has been mistakenly perceived by health and fitness professionals, as well as the general public, as the only means to achieving the established health benefits of physical activity. The majority of exercise and fitness professionals prescribe or recommend exercise programs for their students, clients, or patients based on guidelines from the American College of Sports Medicine (1995). The exercise prescription generally indicates the frequency, intensity, and duration of exercise necessary to increase one's cardiorespiratory fitness level. However, an exercise prescription frequently does not address the underlying question most people want answered, "How little physical activity can I do and still reap health benefits?"

Another possible reason that people are not active is that our high-tech society encourages physical inactivity. We have fancy automobiles that are fun to drive (Why walk?); riding lawnmowers (Why push?); video games and home-entertainment systems (Why go outside?); and numerous labor-saving devices at our workplace (Why move?). These technological advances add convenience, entertainment, enjoyment, and comfort to our lives but can be harmful to our health by promoting a sedentary lifestyle.

A final reason for our inactive society may be social and environmental barriers that act to prevent physical activity. Safe neighborhoods with sidewalks, bicycle paths, and recreational facilities are needed to promote physical activity among Americans (American College of Sports Medicine and U.S. Centers for Disease Control and Prevention, 1993).

Physical Activity Lingo

Professionals must understand the distinction between exercise and physical activity. Physical activity may be defined as any bodily movement produced by skeletal muscles that results in energy expenditure (Caspersen, Powell & Christenson, 1985). Leisure time physical activity (LTPA) involves activity outside of one's job, such as household tasks, sports, or conditioning exercises. The most common LTPAs are walking for pleasure and working on the house or yard (Leon, Connett, Jacobs & Rauramaa, 1987).

Exercise is a subcategory of physical activity. "Exercise is physical activity that is planned, structured, repetitive, and purposive in the sense that improvement or maintenance of one or more of the components of physical fitness is an objective" (Caspersen et al., 1985, p. 128).

What Should I Do?

The current public health recommendation regarding physical activity states:

All Americans should accumulate at least 30 minutes of moderate-intensity physical activity on most, preferably all, days of the week. Those who currently meet these standards may derive additional health and fitness benefits by becoming more physically active or including more vigorous activity (Pate et al., 1995).

This recommendation will be examined and explained in the following sections.

Accumulation

Is one continuous bout of activity more beneficial than multiple bouts throughout the day? Although more research is needed in this area, experts have agreed that intermittent episodes of physical activity are more beneficial than remaining sedentary (DHHS, 1996). Therefore, if you cannot set aside 30 minutes for a walk each day, you can accumulate the 30 minutes by walking for 10 minutes in the morning, 10 minutes in the afternoon, and 10 minutes in the evening. Accumulation of physical activity throughout the day is a reasonable alternative to setting aside an uninterrupted period of time for physical activity each day (DHHS, 1996).

Moderate Intensity

According to Pate et al. (1995), physical activity does not have to be structured or vigorous to enhance health status. Moderate-intensity physical activity that is performed regularly will result in health benefits. In addition, moderate-intensity activities are more likely to be continued throughout one's lifetime than are vigorous activities. Examples of moderate-intensity activities are included in Table 1.

Table 1. Examples of Moderate-Intensity Physical Activities

Home care, general cleaning

Mowing the lawn, push mower 

Home repair, painting

Walking, briskly (3-4 mph)

Cycling for pleasure or transportation (10 mph)

Swimming, moderate effort

Golf, pulling cart or carrying clubs

Fishing, standing/casting

Some people prefer to use caloric expenditure as a method of assessing the intensity of an activity. Physical activity that leads to an increase of daily energy expenditure of approximately 150 kilocalories/day (approximately equivalent to 1,000 kcals/week) is associated with the substantial health benefits mentioned previously (DHHS, 1996). A 150-pound adult can expend 150 kcals/day by raking leaves for approximately 30 minutes or by walking at four miles per hour for 30 minutes.

Most Days of the Week

What is meant by "most" days of the week? To meet the recommendation, an individual must accumulate 30 minutes of moderate-intensity physical activity on at least five of the seven days of the week.

Additional Physical Activity

Increases in physical activity beyond the 30 minutes of moderate-intensity activity yield additional health benefits (DHHS, 1996). Thus, those individuals who already meet the moderate recommendation can expect to gain additional health benefits by increasing their activity. Frequency, intensity, or duration of activity can be increased separately or all at once. In addition, an individual may include some variety into his or her activity program by pursuing additional recreational activities such as hiking or golf.

Meeting The Recommendation

The first step is acknowledging your inactivity and becoming more active in your everyday life. Methods for increasing daily physical activity include walking instead of driving whenever possible, taking the first available parking space you come to in the parking lot instead of jockeying for the space closest to the entrance, and using the stairs instead of elevators and escalators.

Second, start participating in moderate-intensity recreational activities that you enjoy. Start taking the dog for walks or walking with a neighbor. (Remember you can accumulate the recommended 30 minutes of moderate activity in bouts of at least 10 minutes in duration). You can also join a group, club, or team that engages in an activity of interest to you.

Third, once you find that you are more active, you may want to consider increasing your physical activity and perhaps even exercising.

It Is Never Too Late

A study by Paffenbarger et al. (1993) indicated that it is never too late to begin participating in physical activity. Subjects in the study that began participating in physical activity after years of inactivity had reduced mortality rates when compared to those who remained sedentary. This health benefit was apparent even for the men who became physically active after the age of 60. This is great news for sedentary adults who have been contemplating an increase in their physical activity but thought it was too late for any positive impact.

Suggestions for Recreation Professionals

Recreation professionals must promote physical activity. Exercise is an important component of physical activity; however, only 15 percent of our adult population exercises (DHHS, 1996). People should be encouraged and rewarded for participating in moderate-intensity physical activity. Suggestions for recreation professionals are listed in Table 2.

Table 2. Suggestions for Recreation Professionals

1. Encourage people to participate in physical activity (even if the activity would not be classified as "exercise").

2. Develop creative strategies to get people off the couch and moving.

3. Encourage people to build physical activity into their daily routines.

4. Expose people to a variety of physical activities so they can find one or more they enjoy.

5. Promote physical activity for all age groups.

6. Make physical activity FUN.

7. Remember, one is never too old to receive health benefits from participating in moderate-intensity physical activity.

Adapted from Dinger, M. K. (1995).

Conclusions

Research indicates that morbidity and mortality risk is decreased by accumulating 30 minutes of moderate-intensity physical activity at least five days a week. An increase in energy expenditure -- by as little as 150 kcals/day -- can have a positive impact on health status.

Recreation professionals have a responsibility to encourage people of all ages to increase their participation in moderate physical activity as well as in traditional exercise. Just as individuals are praised for exercising at their target heart-rate zones or winning a soccer tournament, we should also praise them for working in their gardens, walking to school or work, and using the stairs whenever possible.

References

American College of Sports Medicine. (1995). Guidelines for exercise testing and prescription (5th ed.). Baltimore, MD: Williams & Wilkins.

American College of Sports Medicine and U.S. Centers for Disease Control and Prevention. (1993). Summary Statement: Workshop on physical activity and public health. Sports Medicine Bulletin, 28(4), 7.

American Heart Association. (1994). Heart and Stroke Facts: 1994 Statistical Supplement. (Available from the American Heart Association).

Caspersen, C. J., Powell, K. E., & Christenson, G. M. (1985). Physical activity, exercise, and physical fitness: Definitions and distinctions for health-related research. Public Health Reports, 100(2), 126-131.

Dinger, M. K. (1995). Leisure time physical activity: How little is enough? Missouri Journal of Health, Physical Education, Recreation and Dance, 5, 11-18.

Leon, A. S., Connett, J., Jacobs, D. R., & Rauramaa, R. (1987). Leisure-time physical activity levels and risk of coronary heart disease and death: The multiple risk factor intervention trial. Journal of the American Medical Association, 258(17), 2388-2395.

Paffenbarger, R. S., Hyde, R. T., Wing, A. L., Lee, I., Jung, D. L., & Kampert, J. B. (1993). The association of changes in physical-activity level and other lifestyle characteristics with mortality among men. New England Journal of Medicine, 328(8), 538-545.

Pate, R. R., Pratt, M., Blair, S. N., Haskell, W. L., Macera, C. A., Bouchard, C., et al. (1996). Physical activity and public health: A recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. Journal of American Medical Association, 273(5), 402-407.

United States Department of Health and Human Services. (1996). Physical Activity and Health: A Report of the Surgeon General. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion.

RELATED ARTICLE: Research into Action: Let's Get Physical

Research Into Action is published monthly by the Society of Park and Recreation Educators, National Recreation and Park Association. As an accompaniment to "Research Update," its goal is to turn research findings into field action by highlighting management strategies. Founding editors are Dr. Ruth Russell and Dr. Daniel D. McLean, Department of Recreation and Park Administration, Indiana University.

Introduction

Regular physical activity is an important protection against coronary heart disease, adult-onset diabetes, hypertension, certain cancers, osteoporosis, and depression. While we have known this for decades, health and fitness research has been equivocal about how much physical activity is necessary to reap these health benefits. This month's "Research Update" provides the latest advice on this question.

Impact of this Research

The current public health recommendation is that we should accumulate at least 30 minutes of moderate-intensity activity on most -- and preferably all -- days of the week. Further, if we become more physically active than this, we may derive additional health benefits. What does this mean? First, in terms of "accumulating," is one continuous period of activity more beneficial than multiple bouts throughout the day? Although more research is needed, some conclude that while a continuous period is best, intermittent episodes of physical activity are more beneficial than remaining sedentary. Second, how active is moderate intensity? Some studies recommend a daily energy expenditure of approximately 150 kilocalories (kcals) per day, translating into a 150pound adult raking leaves for approximately 30 minutes or walking at a four-mph pace for about 30 minutes. Finally, what is meant by most days of the week? Research says at least five of the seven.

How to use this Research

This month, the recommendations for using the reported research focus on individuals rather than organizations:

* Acknowledge your inactivity

* Whenever possible, walk instead of driving

* Take the first available parking space instead of jockeying for the space closest to the entrance

* Take the stairs instead of escalators and elevators

* Participate in enjoyable moderate-intensity recreation activities

* Join a group, club, or team than engages in an interesting activity

* It is never too late to become physically active

* Build physical activity into your daily routine

* Lobby your local park and recreation agency to develop creative strategies that will expose people to physical activity and provide opportunities for individuals to become physically active

For more Information

Pate, R.R.; Pratt, M.; Blair, S.M.; Haskell, W.L.; Macera, C.A.; Bouchard, C.; et al., 1996. Physical Activity and Public Health: A Recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. Journal of American Medical Association, 273:5, 402-407.

Mary K. Dinger, Ph.D., CHES, is an assistant professor in the Department of Health Education and Recreation at Southern Illinois University at Carbondale.

Research Update is edited by Dr. Irma O'Dell of Southern Illinois University at Carbondale.