Physical Activity Health Article

GENETICS, MATURATION, AGE, AND OTHER DETERMINANTS OF ACTIVITY

Studies have shown that some animals tend to be more active than others. Humans are no exception in that a genetic predisposition to be active is one of several factors that determine the daily activity levels of children and adults. While social and environmental factors account for more of the variability in human activity than genetics, there are several ways in which heredity is important.

Physical fitness is highly influenced by heredity, especially in childhood. The amount of variability in physical fitness associated with heredity ranges from 10 percent to as high as 60 percent (e.g., maximal aerobic power, 25%; muscular endurance, 21%; muscle strength, 30%; body fat, 25%; bone density, 30—60%). Evidence suggests that fit people are more likely to be active than unfit people, thus heredity influences activity levels via its relationship to fitness.

Recent evidence also indicates that all people do not respond similarly to regular physical activity. Large variations have been noted between people who have a hereditary predisposition to respond to physical activity and those who do not have this predisposition. In other words, some people have the genetic makeup to respond more favorably to physical activity than others. Given the same activity program, some show considerably greater improvements in fitness than others.

Maturation also influences physical activity and fitness. During puberty, the potential for physical activity to produce gains in fitness is enhanced. Thus, teens are more responsive to physical activity than children. The feedback from performance improvements stimulates an interest in activity among those who are more mature physically compared to those who are less mature and do not see similar benefits for the same amounts of activity. Those who mature early may be more inclined to see the benefits of regular physical activity than those who mature later.

There is an abundance of evidence to indicate that children are the most active group in society. Beginning in the early school years, activity drops consistently throughout life. The most precipitous declines occur during the teenage years. The drop in activity continues throughout life, though the drop from the teens to the early twenties is less dramatic than the drop-off from childhood to the teen years. Older adults (above 50) are typically less active than younger adults. Much of the decline with age can be attributed to decreases in dopamine levels, which are associated with decreases in motivation to be active, though social factors (influence of friends, family, and role models), psychological factors (self-efficacy, enjoyment, beliefs about activity, and barriers to activity), physical factors (weather, safety, convenience, and availability), and demographic factors (sex, education, and vocation) all play a role in adult physical activity patterns.

GUIDELINES AND APPROACHES TO INCREASING ACTIVITY LEVELS

Among the most important physical activity guidelines are those of the ACSM and the CDC, which has established guidelines for the promotion of physical activity among youth. In addition, Healthy People 2010 (2000), a statement of national health goals, includes important national health objectives relating to physical activity and outlines priorities for changing activity patterns of Americans. Important strategies include increasing moderate and vigorous activity, as well as involvement in activities for muscle fitness and flexibility through increased school physical education, decreased television viewing, improved facilities for physical activity, and increased programs to promote walking and cycling as daily life activities. Expanded worksite health-promotion programs, improved health and wellness education, and greater public information access are other strategies that are outlined.

It is important to point out that the physical activity guidelines that are appropriate for adults are not appropriate for children. Appropriate guidelines for physical activity for children, including applications of the physical activity pyramid for younger age groups are available in Physical Activity for Children: A Statement of Guidelines (1998) published by the National Association for Physical Education and Sports.

CHARLES B. CORBIN

ROBERT P. PANGRAZI

(SEE ALSO: Behavior, Health-Related; Centers for Disease Control and Prevention; Chronic Illness; Coronary Artery Disease; Epidemiologic Transition; Foods and Diets; Healthy People 2010; Lifestyle; Nutrition)