Sarcopenia, mobility, and 24h movement behaviours in South African and Scottish older adults across different socioeconomic settings

Mobility relates to the basic human need of physical movement which declines with advancing age. Strong evidence of successful ageing can be found in mobility performance (walking, muscle strength, and physical functioning) evaluation. Previous evidence indicates that physical activity could prevent progression of mobility limitation and promote successful ageing. As such, the overall aim of this thesis is to determine effects of 24-h movement behaviours (physical activity, sedentary behaviour, and sleep) on musculoskeletal health, adiposity, and physical functioning in older adults. Chapter 1 reviews the evidence for these outcomes of interest. Subsequently, chapter 2 reports on changes in walking behaviour with increasing age in high-functioning older adults living in Scotland. However, individual intrinsic capacity is only one of the components of functional mobility and laboratory-based gait analysis can only provide a limited picture. Accordingly, in chapters 3-5, laboratory-based measurements of mobility have been translated into the real world by considering movement within the whole 24-h time period in older adult populations living in Scotland (high-income setting) and South African Townships (low-income setting). Chapter 3 describes compositional time differences in 24-h movement behaviour between Scottish and South African older adults. Chapters 4 and 5 investigates associations between 24-h movement behaviours, musculoskeletal health, adiposity, and physical functioning. Higher volumes of moderate- to vigorous-intensity physical activity were associated with better health outcomes in both samples, while sedentary behaviour presented a detrimental effect on other variables. However, differences in health outcomes associations were present between the Scottish and South African settings. The findings reported in this thesis demonstrates the importance of exploring 24-h movement behaviours in older adults from differing settings, to gain greater understanding of context and socioeconomic profiles, and how these link to health outcomes so that there is an understanding of how best to intervene