Age-related differences in physical activity levels of young adults.

<b>Purpose:</b> To examine age-related differences in the physical activity behaviors of young adults.<br /><br /><b>Methods:</b> We examined rates of participation in vigorous- and moderate-intensity leisure-time activity and walking, as well as an index of physical activity sufficient for health benefits in three Australian cross-sectional samples, for the age ranges of 18–19, 20–24, and 25–29 yr. Data were collected in 1991, 1996, and 1997/8.<br /><br /><b>Results:</b> There was at least a 15% difference in vigorous-intensity leisure-time physical activity from the 18–19 yr to the 25–29 yr age groups, and at least a 10% difference in moderate-intensity leisure-time physical activity. For the index of sufficient activity there was a difference between 9 and 21% across age groups. Differences in rates of walking were less than 8%. For all age groups, males had higher rates of participation for vigorous and moderate-intensity activity than did females, but females had much higher rates of participation in walking than males. Age-associated differences in activity levels were more apparent for males.<br /><br /><b>Conclusions:</b> Promoting walking and various forms of moderate-intensity physical activities to young adult males, and encouraging young adult females to adopt other forms of moderate-intensity activity to complement walking may help to ameliorate decreases in physical activity over the adult lifespan.<br />