Modulating VO2max: effects of training frequency, sprint volume, and myokines

Abstract

Physical inactivity is a global issue; over a third of people don’t exercise regularly enough to meet the recommended physical activity guidelines. This increases the risk of mortality and developing numerous chronic diseases. Regular exercise improves V̇O2max, which is the best predictor of overall health and disease risk. The reasons for low adherence to regular physical activity are multifactorial, with lack of time among the most common reasons reported. Exercise interventions, such as HIIT and SIT, have been well researched as time-efficient alternatives to MICT. Research has demonstrated the effectiveness of HIIT and SIT at improving V̇O2max. However, they are not without their limitations, which cast doubt on their real-world relevance and whether they would improve regular physical activity levels. REHIT has been shown to be a promising alternative, effective at improving V̇O2max to levels similar to MICT, HIIT, and SIT, but with a substantial reduction in total exercise volume. The minimal effective dose for improving V̇O2max with REHIT remains to be determined, and modifications to key parameters remain underexplored. Furthermore, the mechanisms underpinning the comparable V̇O2max improvements observed with REHIT despite its substantially lower exercise volume remain unclear.

Chapter 1 provides an overview of the literature surrounding the thesis topics. Chapter 2 meta-analyses the literature and combines with previous work on the topic to provide an updated meta-analysis and systematic review of the effect of the number of sprint repetitions in a SIT session on the changes in V̇O2max. Chapter 3 presents an experimental trial investigating the effects of reducing the training frequency of a REHIT exercise intervention on the changes in V̇O2max. Chapter 4 attempts to elucidate mechanisms that affect variability in the response to exercise by examining whether there are differences in the training-induced myokine response between high- and low-responders to exercise.