AbstractIsometric exercise training is gaining recognition for its blood pressure (BP) lowering effects. The current thesis had four primary purposes, to: i) assess the reproducibility of various BP and heart rate variability (HRV) measures (ii) validate the CR-10 scale as a novel method for self-regulating the intensity of isometric handgrip (IHG) exercise and iii) determine the effects of self-regulated IHG exercise on resting and 24-hour ambulatory BP iv) investigate levels of participant adherence to self-regulated IHG training. Secondary to these purposes, indirect measures of autonomic function were recorded to provide insight into a possible mechanistic pathway for BP reductions.
Study 1 (Chapter 4) assessed the reproducibility of 24-hour ambulatory BP, 24-hour HRV, resting HRV and resting systolic blood pressure variability (BPV). It was shown that i) the typical error in ambulatory systolic BP recordings reduced over consecutive pairs of measurements (3.8-2.8mmHg) and would therefore benefit from familiarisation periods ii) 24-hour HRV provided superior reproducibility to resting measurements and iii) resting systolic BPV displayed poor reproducibility (coefficient of variation, 27-60%).
Study 2 (Chapter 5) determined the validity of self-regulating IHG exercise as an alternative to the commonly prescribed 30% maximal voluntary contraction (MVC). Findings showed that exercising at “Level-6” on the category-ratio scale (CR-10) enabled participants to produce an appropriate IHG exercise intensity (mean 33% MVC). Thus, the CR-10 scale provides a valid means for participants to self-regulate the intensity of IHG exercise.
Study 3 (Chapter 6) implemented an IHG training programme in a 2-phase training study design. Phase 1 showed that 10-weeks of self-regulated IHG training (at CR-10 “Level 6”) induced clinically-relevant reductions in resting systolic BP (-6mmHg). However, no changes were observed in 24-hour ambulatory BP. The data also displayed trending changes in autonomic modulation of both heart (HRV) and systolic BP (BPV), these findings could offer some explanation for the reductions in resting BP. Phase 2 revealed excellent adherence (average, 95%) during both shorter-term (14 weeks) and longer-term (24 weeks) self-regulated, home-based, unsupervised IHG training. However, despite excellent adherence, the longer-term exercise group did not maintain their reduced resting BP upon completion of 24-weeks of isometric exercise training.
Taken together, these findings demonstrate the appropriateness of self-regulated IHG training as a nonpharmacological intervention for lowering resting BP. However, it seems that the reductions in resting BP may be lost with prolonged training and further investigation into the long-term effects of isometric exercise training on resting and ambulatory BP is required.
|Date of Award||2019|
|Supervisor||Keiran Henderson (Supervisor), Ian Swaine (Supervisor) & Mark Stone (Supervisor)|