The Effect of Intensity Prescription on Individual Responses to Exercise

Abstract

Following exercise training, evidence demonstrates improvements in exercise capacity, symptoms of disease, quality of life, as well as reductions in hospitalisation, morbidity, and mortality. Notably, cardiorespiratory fitness, measured as maximum oxygen uptake (V̇O2max), is associated with all the above. Whilst exercise training increases V̇O2max at the group level, these changes appear to be heterogenous at the individual level. Numerous (non)modifiable factors contribute to response variability. One factor requiring further research is the way exercise intensity is prescribed. The traditional approach is evidenced as inadequate, poorly controlling and normalising exercise intensity among individuals, potentially implicating subsequent acute and chronic responses. Exploring the efficacy of alternative approaches is thus warranted to improve the prescription of exercise intensity and increase the likelihood of individuals experiencing meaningful changes in V̇O2max. This was the inherent aim of the thesis. In Chapter 4, results of a meta-analysis using individual participant data revealed no difference in V̇O2max response variability following either traditional or threshold-based exercise training. However, greater mean increases in V̇O2max were observed following threshold-based exercise training and increased the likelihood of increasing V̇O2max beyond a predefined response threshold. In Chapter 5, it was demonstrated that in response to different exercise bouts, the variability in exercise tolerance and acute physiological responses was lower when exercise intensity was prescribed relative to critical power (a ‘threshold-based approach’) compared to when prescribed relative to V̇O2max (a ‘traditional approach’). In Chapter 6 it was demonstrated that increases in V̇O2max were superior following exercise training prescribed relative to critical power compared to when prescribed relative to V̇O2max. Furthermore, a greater proportion of individuals increased V̇O2max above the predefined response threshold in the threshold group. There was, however, no difference in V̇O2max response variability between exercise groups. The findings of this thesis advocate the use of threshold-based approaches, namely using critical power, to inform and prescribe exercise intensity.