Prevalence of obesity, low physical activity, and poor physical fitness of youth in the United States are increasingly poor and in need of intervention to prevent later concerns like hypertension. The overall goal of this dissertation was to examine which factors weigh heaviest in predicting cardiovascular fitness in diverse youth, and how we might measure those factors by maximizing clinical utility and psychometric properties. The sample was gathered from a larger study examining physical activity in youth from Miami-Dade county enrolled in out-of-school programs. Participants (N = 58) were aged 6-17 and comprised exclusively of Hispanic and Non-Hispanic Black children and adolescents, the majority of whom were from low-income families. Predictors of fitness were gathered in three primary categories: demographic variables (age, gender, race/ethnic category, family income level), body composition (Body Mass Index [BMI] percentile, Bioelectrical Impedance Analysis [BIA]-measured body fat percentage), and habitual physical activity (accelerometer-measured counts per minute). These factors were entered in a hierarchical regression model to predict cardiorespiratory fitness measured by performance on a 20-meter shuttle run. Physical activity was not found to be significantly associated with fitness, and the effect size of this relationship was small, particularly when considering the impact of demographic and body composition variables. Overall, results reinforced the need for interventions to improve body composition and increase physical activity: the average participant was at the 81st percentile of BMI, had 26% body fat, was sedentary for approximately 84% of awake time, and only spent a few minutes per day engaging in vigorous physical activity. There were significant main effects of gender and race/ethnic category such that males and Non-Hispanic Black participants generally spent a greater proportion of time engaging in physical activity, with less sedentary time. Being female, younger, and having less body fat was associated with performance in the healthy fitness range when considering the impact of other variables, even though boys and older participants had more laps on the shuttle run. Findings presented in this dissertation indicate a continued need to develop technology with high utility, validity, and reliability to measure and improve indicators of health in diverse, low-income youth.

The problem of this study was to determine the effects of four dynamic exercise programs on physical fitness as measured by selected items from the American Association for Health, Physical Education, and Recreation Youth Fitness Test.

Regular moderate-vigorous physical activity (MVPA) is associated with significant physiological and psychological health benefits (Department of Health, DoH, 2004). However, many children are not undertaking recommended levels of physical activity (PA) (DoH, 2009). This research examined relationships between physiological health parameters, psychological determinants and PA levels in 10-14 year old schoolchildren (N = 249) and assessed the influence of three school-based PA interventions on these constructs in the context of the Health And Physical activity Promotion in Youth (HAPPY) study. Study 1 revealed that sedentary behaviours, moderate PA (MPA), vigorous PA (VPA) and MVPA levels were higher on weekdays than weekend days (p < .001). However, schoolchildren’s PA is often difficult to measure accurately. The self-report measure utilised in study 2 underestimated total MVPA versus accelerometry for both sexes on weekdays and girls on weekend days (p < .01). However, study 3 highlighted a lack of agreement between two RT3® triaxial accelerometer cut-offs for all activity categories. The importance of VPA for promoting health was highlighted in the updated PA guidelines (DoH, 2011). Study 4 reported that cardiorespiratory fitness (CRF) was positively associated with VPA but not MPA (β = .27, p < .01) and inversely correlated with measures of body composition (% body fat; body mass index; waist circumference) (r = -.74, r = -.60, r = -.39, p < .001). Knowing the health benefits of regular MVPA and VPA, it is important to understand the determinants of PA intentions and behaviours to more effectively promote PA in less active children (studies 5 and 6). An exploratory analysis of the constructs in the Revised Theory of Planned Behaviour and the Modified Social Learning Theory for children predicted PA intentions (R2 = .38, F(5, 171) = 20.19, p < .001; R2 = .13, F(6, 147) = 3.4, p < .01, respectively) but the constructs in either model were unable to predict PA. Recognising the need to promote PA levels, study 7 investigated the effectiveness of three school-based interventions (vs. control) on outcome variables included in studies 1, and 4-6. The Health Education and Psychology Health Promotion conditions produced significant positive change scores between data collection 2 and 3 for CRF (vs. control) whereas the Youth-Led condition produced significant change scores between baseline and data collection 2 for generalised self-efficacy (vs. control). No significant change scores were reported for PA, the RTPB constructs or intentions. In conclusion, this research has emphasised the importance of employing a multidisciplinary approach to aid understanding of schoolchildren’s PA levels. Specific highlights include low weekend day PA as a possible future PA promotion target, although it is vital that accelerometry cut-points are standardised, and the relevance of VPA and body composition in predicting CRF. The psychological models identified some important determinants of PA intentions, but a prominent intention-behaviour gap and a need for more intensive interventions to promote PA levels was apparent.

The purpose of this study is to measure the physical fitness levels of Navajo girls fourteen to sixteen years of age using the AAHPER Youth Fitness Test and to establish norms based upon scores determined from test results from seven schools. These norms are also compared to national norms found in the manual accompanying the AAHPER Youth Fitness Test. The results of this study give an indication of the overall fitness level of fourteen-, fifteen-, and sixteenyear-old Navajo girls. Of the seven test items, the Navajo norms were below the national norm on five items and above on the softball throw and 600 yard run-walk