Physical activity profiling of New Zealand adults: a study of adults with and without young children
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Physical activity is essential for optimal health and wellbeing for all people. Emerging epidemiological perspectives call for a move from the current focus on moderate-to-vigorous physical activity (MVPA) to a whole-of-physical activity approach, where understanding of physical activity accumulated in all areas of life and at all intensities is important. A key driver of this perspective has been developments in measurement technology which have enabled a broader assessment of physical activity than previously possible. This objective measurement allows the volume and patterns of physical activity at various intensities to be explored, in order to develop a more complete profile of physical activity behaviour that may lead to better health promotion messages. Adults with young children provide an ideal population for physical activity profiling. These adults can experience considerable time constraints and psychosocial influences for participation in purposeful physical activity; however, they are also likely to have distinct sources and patterns of physical activity that have gone undetected in previous studies. This body of work provides a first step towards a broader understanding of physical activity in adults with and without young children. To start, issues for measuring physical activity in adults with young children were explored (Chapters 3–4); outcomes from these studies highlight substantial limitations to the existing body of knowledge of physical activity in this population. In particular, an overreliance on self-report tools has meant that current knowledge is biased towards MVPA undertaken during leisure-time, and there was an incomplete picture of parental physical activity. These findings provided the basis for development of the subsequent studies to construct a complete profile of parental physical activity, and to investigate whether dimensions of physical activity differed between those with and without young children. The following three studies explored various dimensions of accelerometer-derived physical activity, in terms of overall amounts (steps and accelerometer counts) at various intensities, hour-by-hour patterns, and patterns of activity accumulation (frequency and duration of bouts at various intensities). A novel approach was used to generate an overall profile of physical activity for those with and without young children, which synthesised the interplay between time spent in sedentary, light, and moderate-to-vigorous intensities (Chapter 6). These studies are the first to investigate physical activity across all intensities in adults with young children and to report objectively-measured sedentary time and light-intensity activity in this population. Overall, adults with young children spent more time in light-intensity physical activity, and less time in sedentary and MVPA than adults without children. Differences in the overall amount of physical activity (total steps per day) were generally trivial between groups. Hour-by-hour analyses revealed distinct variations in how physical activity was structured through the day between those with and without young children, and minute-by-minute analyses demonstrated that adults with young children accumulated MVPA and sedentary time in shorter bouts than those without young children. A novel and important finding was that adults with and without young children showed distinct profiles of physical activity; those with young children showed patterns of movement throughout the whole day, whereas adults without children displayed distinct periods of high sedentary time offset by periods of MVPA. The challenge for public health is to acknowledge differences in patterns of living that result in different profiles of physical activity behaviour, and to develop relevant and targeted health promotion messages that lead to sustainable behaviour change. For this to occur, a considerable amount of work is needed to determine more precise dose-response relationships with different amounts, types, and patterns of activity.