| dc.description.abstract | Dynamic cerebral autoregulation (dCA) describes the active maintenance of cerebral blood flow (CBF) in response to rapid, systemic blood pressure (BP) fluctuations. dCA capacity has been linked to neurological pathologies such as dementia, stroke and traumatic brain injury and may be implicated as a target for therapeutic strategies. Resistance exercise is a common leisure activity with growing popularity and forms the basis for many strength sports as well as being recommended by public health institutions. Heavy resistance exercise is known to induce large transient increases in BP which are translated into elevations in CBF. dCA must act effectively to minimise the BP oscillations which are translated into the cerebrovasculature, however CBF is still significantly elevated which indicates that it is not entirely effective at maintaining a constant CBF. This begs the question: does resistance exercise lead to altered dCA capacity both acutely and/ or at baseline following years of training? This thesis is formed of two main sections. Firstly, the within- and between-day reliability of dCA metrics phase, gain and normalised gain at each phase of the cardiac cycle were determined using repeat squat-stand manoeuvres (SSM) to elicit orthostatic BP fluctuations. As dCA can be induced, measured and analysed with a variety of methods, understanding the reliability of the measures used is crucial when interpreting one’s results. SSM were utilised to elicit BP fluctuations at 0.05 and 0.10Hz due to the excellent signal-to-noise ratio which they produce. The novelty of this work is largely attributed to the exploration of dCA metrics during systole and diastole as well as mean values, both within- and between-day. Secondly, the acute effects of resistance exercise and long-term effects of regular resistance exercise on dCA are examined. Long-term effects were inferred by comparing phase, gain and normalised gain in resistance trained vs. recreationally active individuals by use of SSM in a rested condition. Acute effects were explored by comparing phase, gain and normalised gain pre-exercise to follow-up measures 10 and 45 minutes post- 3 exercise in both groups. The exercise protocol consisted of four sets of ten repetition back squats at 70% of the individuals one-repetition maximum. This work indicates that dCA induced by SSM at 0.05 and 0.10Hz produce excellent reproducibility of phase, gain and normalised gain within- and between-day when measured as the mean of the cardiac cycle. Diastolic and systolic outcomes were also largely reproducible, although notably less so than mean values. Cross-sectional analysis of baseline dCA between groups found no significant differences in phase, gain or normalised gain at any phase of the cardiac cycle. Furthermore, no group interaction effect was identified in response to an acute bout of resistance exercise, suggesting that the post-exercise effects on dCA were similar in both demographics. dCA was largely unaltered following resistance exercise; however, gain and normalised gain were significantly elevated when measured as the mean and systolic section of the cardiac cycle during 0.10Hz SSM only. This difference was only present 10, but not 45 minutes post-exercise which indicates rapid recovery towards baseline. Further research is warranted, but these preliminary findings suggest that resistance exercise may acutely impair sympathetic nervous activity responsible for CBF regulation, although this does not appear to lead to alterations at baseline. | en_GB |
