The Incidence of Cardiorespiratory Fitness Training and Cardiometabolic Risk Factor Responsiveness Following Individualised and Standardised Exercise Prescription
There is individual variability following cardiorespiratory fitness (CRF) training leading to the terminology of CRF ‘responders’ and ‘non-responders,’ yet the underlying cause of the variability is not well understood. Traditionally, a standardised approach to exercise prescription has utilised relative percentages of maximal heart rate (HR), heart rate reserve (HRR), maximal oxygen consumption (VO2max), or VO2 reserve to establish exercise intensity. This ‘one size fits all’ model fails to take into consideration individual metabolic responses to exercise and may be related to the variability in training responses. Therefore, the purpose of this thesis was to better understand training responsiveness following 12 weeks of CRF training between a standardised and individualised exercise intensity prescription.
A total of 49 and 20 inactive experimental and control participants, respectively, were recruited for the investigation from a community wellness program and the surrounding community via advertisement at the local university, newspaper, and word-of-mouth. In a subgroup of the main experimental participants, a TE of 4.7% in VO2max was established from a coefficient of variability following repeated testing at baseline. Therefore, it was deemed that participants needed to have a %Δ > +4.7% in VO2max (ml·kg-1·min-1) to be considered a training responder following the 12-week intervention.
Training prescription in the individualised group was anchored based on the first (VT1) and second ventilatory threshold (VT2) with exercise intensity starting below VT1, increasing to between VT1 and VT2, and ending the exercise protocol with a HR above VT2. The standardised group had exercise intensity based on percentages of HRR with a progression from 40% to 65% of HRR throughout the 12 weeks. The control group was asked to maintain their regular day-to-day lifestyle.
In an analysis of time course changes, it was revealed that both groups had a significant change (p<0.05) at week 8 and 12 compared to baseline values. However, only the individualised group showed a significant increase from week 8 to 12. CRF responsiveness (measured by changes in VO2max) was significantly different between groups with responsiveness of 100% and 60% for the individualised and standardised groups, respectively. VO2max significantly increased for the standardised and individualised groups from 24.3±4.6 to 26.0±4.2 ml·kg-1·min-1, and 29.2±7.5 to 32.8±8.6 ml·kg-1·min-1, respectively. Absolute VO2max significantly increased from 2.0±0.6 to 2.2±0.6 L·min-1, and 2.4±0.8 to 2.6±0.9 L·min-1 for the standardised and individualised groups, respectively. The overall changes in cardiometabolic factors were analysed based on changes in MetS z-scores (i.e. combination of fasting blood glucose, lipids, triglycerides, blood pressure, and waist circumference). However, MetS z-scores did not show a significant difference between individualised and standardised groups, but trends suggested that an individualised approach to the exercise prescription may have a positive effect on these outcomes.
The main finding of this thesis was that an individualised continuous aerobic exercise intensity prescription is superior to a standardised method when investigating training responsiveness. It is believed the mechanisms are related to an individualised approach taking into consideration individual metabolic characteristics.