Background: The level of activity in an individual can be the difference between health and illness. Physical inactivity can cause diseases such as osteoporosis and type-2 diabetes. It has been reported that children live an increasingly inactive life, with less than the recommended a total of 60 minutes daily for children and adolescents of 6-17 years of age. Objective: The objective was to compare two activity diaries and how the results correspond to measurements by an activity meter. Material and methods: This study included 12 children who each carried an activity meter for four days to measure Total Energy Expenditure. In parallel, they filled in two different activity diaries. In the diaries two different calculation methods were used, with a Physical Activity Ratio value or a Metabolic Equivalent of Task value which then was inserted into equations to calculate Total Energy Expenditure. Anthropometric measurements were obtained by use of a stadiometer, a caliper and a bioimpedance scale. Results: The results from the Physical Activity Ratio diary indicated a better match with the results from the activity meter. Conclusions: Between the two diaries significant difference in how the activities were estimated were found, where an overestimation could be seen in the diary that used the Metabolic Equivalent of Task. Differences could also be seen between the activity meter and both diaries, also here the difference were bigger with the Metabolic Equivalent of Task diary. The Physical Activity Ratio diary was better matched with the activity meter.

Physical inactivity and disconnection from natural environments threatens human health. However, research has demonstrated that natural environments potentially support health-enhancing physical activity which could confer greater physical and mental health benefits than physical activity in other types of environment. This thesis approached the study of physical activity in natural environments through three related pieces of research. Firstly, an experimental study was carried out to explore how the presence of litter in beach environments affected psychophysiological responses to exercise. Responses to exercise did not differ in littered and clean conditions but there was evidence that order effects influenced findings. Visual attention to the two scenes differed, but did not mediate differences in psychophysiological responses. Secondly, analysis of a national dataset was undertaken to explore the form and quantity of physical activity conducted within natural environments in England. A series of linear regressions revealed that higher-intensity physical activities occurred in countryside environments, but more total energy expenditure occurred in coastal environments. Thirdly, a quantitative content analysis of brochures which promote recreational walking in natural environments was conducted which investigated their use of persuasive behavioural messages. These brochures omitted behavioural techniques which may be effective at motivating inactive individuals to walk. Extending this, an online survey tested whether improving brochure content heightened intentions to walk in natural environments. By designing content based on the theory of planned behaviour, the intentions of inactive individuals to undertake walking in natural environments were increased. The findings from this thesis demonstrate that the protection of natural environments is vital for preserving and promoting active recreation and could contribute to population-level increases in physical activity with theory-based promotion in the future.