Degree Name

Doctor of Philosophy


University of Wollongong. Faculty of Health and Biomedical Science


Physical inactivity, as a modifiable risk factor for a number of chronic diseases, is now a key public health concern. Age-related declines in leisure-time physical activity have been reported across the entire lifespan. Recent findings based on analyses of large cross-sectional and longitudinal data sets suggest that there is a steady decline in physical activity during the young adult years. Given the evidence linking sedentary lifestyle with increased risk for coronary heart disease and other chronic diseases, health experts have concluded that an important health objective is to increase physical activity levels among all persons including adolescents and young adults. Long-term health behaviour patterns are being established during the early years of young adulthood.

In Chapter 2, age-related differences in the physical activity levels of young adults are examined in three cross-sectional samples of young Australian adults. Prevalence of moderate-intensity and vigorous activity, and walking are described for three age ranges (18 to 19,20 to 24 and 25 to 29 years). Estimated energy expenditures derived from self-reported activity were used to classify respondents as 'sufficiently physically active for long-term health benefits', using a threshold of 800 kcallweek as the cut-point. There were significant differences between successive age groups, with lower proportions of young adults in moderate-intensity and vigorous activity, and being sufficiently active for long-term health benefits. There was a 15% age-related decrease in vigorous leisure-time physical activity participation from the 18 to 19 year old group to the 25 to 29 year old group, and a 10% age-related decrease in moderate leisure-time physical activity. Rates of walking showed slight downward trends with age (less than 8%), but these were not significant. Males were found to have higher rates of overall moderate-intensity and vigorous leisure-time physical activity than females in each of the age groups examined, and consequently had higher rates of sufficient physical activity than did females. Females however, reported higher rates of participation within each of the age groups for walking than did males. While both males and females showed decreases in participation across these age groups, the decrease was greater for males over the entire (18 to 29 years) age range.

Chapters 3 and 4 of this thesis examine factors related to being insufficiently active among young adults. Chapter 3 examines the personal, social and environmental factors associated with young adults being insufficiently physically active for health benefits. Based on energyexpenditure estimates, derived from self-reported activity, thirty-seven percent of the sample did not participate in levels of physical activity sufficient to achieve long-term health benefits. Females were more likely to be insufficiently active, with a higher proportion in the sedentary and low-activity categories than males. Sixty percent of the sample perceived they were doing less activity currently than they did as high school students. A social learning perspective based on Sallis & Hovell' s model (1990) was applied to identify potentially modifiable factors associated with physical activity. For females, predictors of being insufficiently active were lower social support from family and friends, lower enjoyment of activity and being unemployed, and for males, lower social support from friends.

Chapter 4 reported physical activity preferences, preferred sources of assistance to be active and motivators for activity for insufficiently active young adults. Males and females expressed different preferences for physical activity, and different motivators to being active. While the overall most-preferred physical activity choice was racquet sports, there were strong gender differences for activities. Females preferred aerobics, walking, dance and yoga, and males preferred weight training and team sports. Both males and females were found to express similar choices for assistance to be more active. The strongest preferences overall for assistance to be more active were for a group to exercise with, a trainer's advice, and having more facilities. Significantly more females than males wanted a group to exercise with. Significantly more males chose no form of assistance, and more females chose a video or a group to exercise with. Males were motivated to be active by weight gain, while females were motivated by weight loss, muscle tone, opportunities for exercising closer to home, feeling good and looking better.

Chapter 5 examines correlates of Stages of Change for moderate-intensity and vigorous physical activity in young adults. Separate staging measures that reflect guidelines for moderate-intensity and vigorous activity were used. The test-retest reliability of the staging measures was 'fair' for moderate-intensity activity and 'moderate' for vigorous activity. Ratings of barriers to physical activity and motivators for activity were factor analysed separately to produce three barriers factors: personal barriers, environmental barriers and competing demands, and two motivator factors: personal motivators, and environmental motivators. These factors were examined in relation to Stages of Change, separately for moderate-intensity and vigorous physical activity. When staged by the vigorous physical activity measure, significant differences emerged for personal barriers between Stages of Change, for both males and females. Those in Action and Maintenance perceived fewer barriers than did those in the earlier stages. When staged by the moderate-intensity activity measure, significant differences emerged for personal barriers between Stages of Change for females only. Females showed significant differences in personal and environmental motivators between Stages of Change for both moderate-intensity and vigorous activity. Those in Precontemplation identified fewer motivators than did those in the Preparation, Action and Maintenance stages. There was considerable variation by Stages of Change for both moderate-intensity and vigorous physical activity in the barrier and motivator factors for females. For males, there were differences between Stages of Change for vigorous activity for personal barriers only.

The findings from these studies and the implications for promoting physical activity in young adults are discussed in Chapter 6. These findings can be used to target intervention approaches to specific subgroups, such as chronically sedentary women or previously active men. Suitable physical activity promotion strategies and programs could feasibly be designed within campus settings.