Associations of Physical Activity and Vascular Health

Abstract

Current public health guidelines recommend adults achieve 150 minutes/week of moderate-vigorous physical activity (PA) to reduce the risk of cardiovascular disease. However, little is known about how PA should be accumulated to provide the greatest protection to the vascular system. The aim of this thesis was to provide the first detailed understanding of associations between PA and vascular health, and in particular, whether the pattern of PA accumulation is important, over and above PA volume. Chapter 2 describes a systematic review and meta-analysis which characterises the nature and magnitude of associations of PA with vascular health in the existing literature. Chapters 4-6 investigate cross-sectional associations in a large cohort study between PA volume (Chapter 4), the influence of PA patterns between- and within-days (Chapter 5) and the time-of-day of PA (Chapter 6) with indices of vascular health. Chapter 7 describes an experimental study investigating the importance of the proximity of PA prior to post-prandial hyperglycaemia for vascular function. Principal findings support previous evidence that higher volumes of PA are associated with better vascular heath, and that the association is stronger in those with Type 2 Diabetes Mellitus. This thesis provides new evidence that beyond the overall volume of PA, the pattern in which PA is accumulated is additionally important for both macrovascular and microvascular health. In particular, a PA pattern characterised by lower inter-daily stability, and higher between- and within-day variability may be most beneficial. This highlights opportunities for future public health and clinical guidance to extend beyond simplistic “more is better” approaches, and additionally provide more options on how to “move differently”. Future prospective studies are needed to confirm the present findings before pattern-based recommendations could be realised. However, this thesis provides a foundation for future research, and challenges current public health guidance which suggests how PA is accumulated is immaterial.