Engaging in muscle strengthening activities (MSA) as part of a physical activity program offers health benefits. Although the merits of physical activity are well documented, many adults fail to meet appropriate levels as recommended in the 2008 Physical Activity Guidelines for Americans (PAGA). To get a more complete understanding on an individual's physical activity behaviors, the Tracking Resistance Exercise and Strength Training (TREST) internet based survey was developed. The purpose of the current study was to determine the test-retest reliability of TREST items. Additionally, the prevalence of participants meeting the 2008 PAGA was reported by gender. The survey was completed approximately two weeks apart by 224 (52% male) undergraduate kinesiology students. Analysis of the survey items presented TREST as a reliable instrument in assessing an individual's physical activity behavior with a focus on MSA. Among the convenience sample of 445 participants (56% male) that completed the survey in assessment #1, 73% met the 2008 PAGA minimum recommendations for MSA (>=2 days/week) and aerobic activity (>= 150 min MVPA). A more complete MSA and MVPA criteria was established (requiring MSA of all seven major muscle groups) and only 32% of participants met this guideline. In general, men engaged in aerobic exercise and MSA more than women. These results cannot be generalized due the age, activity level, and education of the study's participants. Future studies should investigate the validity of TREST items among a sample of varying fitness levels, races/ethnicities, ages, and educational levels.

Worldwide, there is a growing burden of non-communicable diseases (NCDs). The rise has coincided with the increase in prevalence of overweight and obesity. The ANGELO framework recognises the role of environmental influences in weight gain. In Africa, various environmental influences have led to shifts from a traditional dietary patterns and more physical lifestyles to a “Western” dietary pattern and low physical activity. The life course perspective posits that excessive body weight can persist from adolescence to adulthood, and increase the risk of NCDs. Among adolescents the school environment is a crucial setting for the development of and, or engagement in unhealthy dietary and physical activity behaviour. The aim of this thesis was to investigate in the school environment, the consumption of energy dense foods (EDFs) and energy dense beverages (EDBs) as are typical of a “Western” dietary pattern, and physical inactivity among a sub-group of adolescents in Nairobi, Kenya. Also, the sources of food in the school environment, and the attitudes to the importance of diet and physical activity for health were assessed. A cross-sectional survey was conducted among 402 adolescents aged 13-19 years. The adolescents were recruited from schools that cater to students from households likely to be of at least middle-income socio-economic status. Results indicate that the majority of adolescents reported the consumption of an EDB (82.3%) and EDF (88.3%) at least once during the school day. Nearly half of the adolescents consumed a meal sourced from a school lunch program (45.9%). In terms of weekly consumption, the items that were reported as frequently consumed by the highest proportion of adolescents were sugar sweetened beverages (46.5%), and pastries such as biscuits and cakes (38.8%,). Both the occasional and frequent participation in team sports (50.5%) more common than individual (27.4%) and gym based workouts (26.4%). The majority (88.1%) of adolescents acknowledged the importance of diet and exercise for health. Rigorous measurement of diet and physical activity behaviour and knowledge and attitude of health behaviour in this thesis was limited. Also, the sample used was not representative of adolescents in Kenya. The findings of this thesis are preliminary and further research is recommended using a representative sample and validated data collection methods. Research of this nature can be used in the adoption of school food and exercise policies to promote healthy behaviours and, on a national level, the development of dietary guidelines for adolescents.

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Physical education is important to promote physical activity of adolescents with and without disabilities, but many adolescents are not active during physical education classes. Innovative instructional strategies are imperative to change this phenomenon, but it will be challenging to develop effective instructional strategies without thorough understanding of students' physical activity behavior in physical education settings. Two studies were conducted to comprehensively understand physical activity behavior of adolescents with and without disabilities in inclusive physical education classes at middle schools. The first study investigated the utility of the integrative theory to predict students' physical activity intentions and behavior at the intrapersonal level. A total of 577 participants, including 24 adolescents' with disabilities, were recruited from 8 middle schools in Korea. In a prospective design, participants' psychosocial constructs and physical activity data were collected by survey questionnaires and electronic pedometers. A multilevel (design-based) structural equation modeling using maximum likelihood estimation with robust standard error correction found that students' attitudes, subjective norms, and barrier-efficacy significantly predicted students' goal intentions. Students' implementation intentions and task-efficacy were significant predictors of physical activity behavior. In addition, implementation intentions completely mediated the relationship between goal intentions and physical activity behavior. The second study investigated three conceptual models, including process-product model, student mediation model, and ecological model, to predict students' physical activity behavior at the interpersonal and environmental levels. A total of 13 physical educators teaching inclusive physical education and their 503 students, including 22 students with disabilities, were recruited from 8 middle schools in Korea. A series of multilevel (model-based) regressions with maximum likelihood estimation showed that the ecological model was the most effective model in prediction of students' physical activity behavior. Specifically, it was found that teachers' teaching behavior and students' implementation intentions were significant predictors of the students' physical activity behavior when interacted with gender, disability, lesson contents, instructional models, and class locations. In conclusion, findings suggest that intrapersonal, interpersonal, and environmental predictors provide a systematic account in the understanding of students' physical activity behavior in physical education settings. Future studies should consider all three factors simultaneously to effectively develop instructional strategies that promote physical activity of adolescents' with and without disabilities in physical education classes. / Graduation date: 2013