- Title
- Exercise response and exhaled volatile organic compounds
- Creator
- Bell, Leo
- Date
- 2024
- Type
- Text; Thesis; PhD
- Identifier
- http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/204840
- Identifier
- vital:20091
- Abstract
- A growing body of research features the variability of responses to exercise training, frequently showing approximately 30-40% of participants do not experience meaningful improvements in fitness (also known as ‘nonresponse’). Hence, researchers have focused on investigating determinants of responsiveness to optimise exercise interventions at a personalised level and mitigate the prevalence of nonresponses. This PhD thesis aims to advance knowledge of these factors and provide future directions for research into potential biomarkers for monitoring exercise response. Interindividual variability in response to exercise is determined by a combination of biological (e.g. age, sex, genetics), environmental (e.g. lifestyle, diet, physical activity), and methodological factors (e.g. exercise dose, study design, statistical approach). While genetics are a large component of interindividual variability, studies comparing exercise response in twins indicate genetics may not play as substantive role as originally thought. Additionally, mRNA expression is tissue-specific, expensive, and invasive. Therefore, to improve the incidence of exercise fitness response it is imperative cost-effective, practical, and less invasive molecular predictors of exercise response are identified. This work highlights the potential of exerkines, circulating cell-free DNA, and metabolomic profile changes in blood, saliva, and breath as candidate biomarkers. Exercise studies mainly use reporting measures at the group level (e.g. mean, standard deviation). However, central tendency measures fail to highlight the interindividual variability and capture the proportion of nonresponses. This thesis demonstrates the merit of applying statistical frameworks for assessing interindividual variability and classifying individual responses to exercise training. A study examined whether progressively increasing treadmill run intensity would improve the proportion of positive cardiorespiratory fitness responders compared to constant intensity training. The findings show a significantly higher proportion of positive responders in the progressive overload group, however, a notable percentage of participants (~33%) did not exceed the technical error and smallest worthwhile change threshold (128.2mL). The following study examined the impact of different supervision types on individual responses to exercise training in tertiary education employees. Personal supervision led to the most significant improvements in cardiorespiratory fitness, muscular strength, and body composition compared to non-personal supervision and unsupervised training. Analysis of individual responses indicated a reduced incidence of non-responses for muscular strength and total fat loss, but not V̇O2peak, for personal supervision compared to other supervision types, suggesting that personal supervision can improve individual responses to exercise training. Additionally, the analysis supports evidence that outcome responses do not aggregate consistently within participants. These findings, in combination with the first study, highlight the need to develop measures capable of screening and predicting the likelihood of response to exercise. Breath analysis is a promising non-invasive method for monitoring physiological and metabolic adaptations. Consequently, a breath testing method was piloted to identify potential exhaled volatile organic compounds for monitoring exercise response. Using glass tubes and solid-phase microextraction fibres paired with gas chromatography-mass spectrometry, a non-targeted analytical approach was employed to speculate for volatile organic compounds of interest. The descriptive analysis highlights compounds from endogenous, exogenous, and mixed origins before, 10 minutes and 24 hours after a standardised 20-minute treadmill run. Metabolites of interest included monoterpenes, alkenes and dienes, ketones, aldehydes, alcohols, organosulfur, alkanes, amines, and amides. The presence of certain metabolites was transient and highlighted the confounding influence of the environment on breath sampling. In a follow-up study, the reliability of two commonly abundant compounds, acetone and isoprene, and their dynamic responses across time points are reported. The reliability analyses showed that acetone has poor reliability and consistency within individuals, while isoprene shows moderately good reliability and consistency. Isoprene levels significantly decreased 10 minutes after exercise and returned to baseline after 24 hours, aligning with existing theories on their dynamics. In summary, this thesis aims to highlight the prevalence of non-response to generic training regimens by reporting the relative importance of progressive increases in exercise intensity and the impact of supervision type on individual responses to exercise training. Additionally, this thesis reports on the potential of breath analysis to be a viable biomarker of trainability and suggests future directions for research in this area.; Doctor of Philosophy
- Publisher
- Federation University Australia
- Rights
- All metadata describing materials held in, or linked to, the repository is freely available under a CC0 licence
- Rights
- Copyright Leo Bell
- Rights
- Restricted access by author until 19 December 2026
- Subject
- Exercise; Exhaled volatile organic compounds; Interindividual variability; Reliability
- Thesis Supervisor
- O'Brien, Brendan
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