The effects of isometric exercise training on resting blood pressure with specific reference to selected cardiovascular, neuromuscular, and metabolic variables

There were two purposes to the work of this thesis (a) to identify the role of isometric training intensity in the training-induced reductions in resting blood pressure, and (b) to identify whether the mechanism for the reduced resting blood pressure is best reflected in what can be broadly termed cardiovascular, neuromuscular or metabolic markers of that training. Firstly, in a cross-sectional study, the only strong correlation was found between heart rate variability (a cardiovascular marker) and resting blood pressure. Secondly, this cardiovascular marker was also significantly affected by a single session of isometric exercise, an effect that persisted for at least 4 hours after exercise. However,
thirdly, this marker and other cardiovascular markers (such as cardiac output and stroke volume) did not correlate with reductions in blood pressure seen after 4 weeks of isometric training. Instead, the training-induced reductions in blood pressure correlated strongly with neuromuscular and metabolic markers of isometric training. The extent to which local muscle fatigue was induced during isometric training correlated with the reductions in resting blood pressure. Therefore (a) isometric training intensity appears to
be of utmost importance in the reductions in resting blood pressure (when bilateral-leg exercise is performed in 2 minute bouts), and (b) the mechanism whereby the adaptations in resting blood pressure occur is best reflected in neuromuscular and metabolic markers of local muscle fatigue during that training. These findings are discussed with a particular focus on the possible role of muscle metaboreceptor stimulation, during isometric training in the mechanism of training-induced reduction in resting blood pressure.