Dissertation
Energy availability and within day energy balance in female team sport athletes
Doctor of Philosophy, University of the Sunshine Coast, Queensland
2026
DOI:
https://doi.org/10.25907/01115
Abstract
Low energy availability (LEA) is increasingly recognised as a contributor to adverse health and performance outcomes in athletes, however, its assessment in free-living environments remains methodologically challenging. This thesis investigated energy availability (EA) and within day energy balance (WDEB) in female team sport athletes, with a focus on the prevalence and characteristics of LEA risk, the validity of wearable technologies for estimating exercise energy expenditure (EEE) and the practical application of nutrition interventions during pre-season training. This thesis is comprised of six chapters, three of which are peer-reviewed published research studies. An initial observational study conducted in 11 female soccer players demonstrated that athletes fail to sufficiently increase energy and carbohydrate intake in response to training demands, resulting in no athlete achieving an EA >45 kcal·kg FFM⁻¹·day⁻¹. Despite a high prevalence of LEA risk identified via questionnaires and clinical indicators, no associations were observed between these markers and calculated EA or WDEB. However, overnight glycaemic variability was positively associated with EA (r = 0.722, p = 0.012), suggesting potential utility as an objective marker of EA. The subsequent validation study conducted in a cohort of 31 trained females highlighted substantial limitations in the accuracy of wearable devices (Actiheart 5 and GENEActiv) for estimating EEE during intermittent high-intensity and resistance exercise. While individual calibration improved the accuracy of a multi-sensor device (Actiheart 5) during intermittent exercise (mean absolute percentage error: 4.9%; mean bias: 4.5 ± 60.4 kcal) and achieved equivalence with indirect calorimetry at the group level, substantial individual error remained (95% LOA: -113.9 to 122.8 kcal). Neither device demonstrated acceptable validity for estimating resistance EEE. These findings highlight the ongoing challenges associated with accurately quantifying EEE and, consequently, EA, in applied settings. The intervention study demonstrated that a food provision strategy successfully increased carbohydrate intake and EA during pre-season in female rugby athletes (6.3 ± 0.2g vs 3.1 ± 0.2g carbohydrate·kg⁻¹·day⁻¹, p = 0.001; 45.0 ± 5.8 vs 29.9 ± 5.8 kcal·kg FFM⁻¹·day⁻¹, p = 0.001). However, this improvement in EA did not translate into measurable differences in training adaptations, physique biochemical markers or most sleep metrics over the seven week period. Given the applied setting and limited sample size (n = 13), this study was designed as an exploratory investigation to generate preliminary estimates of effect and inform future research. Collectively, this thesis demonstrated that inadequate fuelling during pre-season is common among female team sport athletes and that current methods for assessing EA in free-living environments remain limited. Practical, guideline-based nutrition support effectively increased carbohydrate intake and EA but did not produce measurable improvements in health or performance outcomes within the small exploratory cohort. Together these findings support a shift in how LEA risk is conceptualised and monitored in applied sport settings. Rather than relying solely on calculated EA as a definitive metric, future approaches may benefit from integrating multiple indicators of nutrition adequacy, including sports nutrition guideline adherence and emerging objective biomarkers such as glycaemic variability. Future research should prioritise the development of sport-specific calibration methods for wearable devices used to estimate resistance EEE, and evaluate whether failure to meet contemporary carbohydrate guidelines provides a practical indicator for LEA risk across diverse athletic populations.
Details
- Title
- Energy availability and within day energy balance in female team sport athletes
- Authors
- Rebekka Frazer - University of the Sunshine Coast, Queensland, School of Health - Nutrition & Dietetics
- Contributors
- Gary Slater (Principal Supervisor) - University of the Sunshine Coast, Queensland, School of Health - Nutrition & DieteticsFiona Pelly (Co-Supervisor) - University of the Sunshine Coast, Queensland, School of Health - Nutrition & DieteticsAmy-Lee Bowler (Co-Supervisor) - University of the Sunshine Coast, Queensland, School of Health - Nutrition & DieteticsChristopher Askew (Co-Supervisor) - University of the Sunshine Coast, Queensland, Healthy Ageing Research ClusterGregory Cox (Consultant Supervisor) - Bond UniversityDominique Condo (Consultant Supervisor) - Deakin UniversityLouise M Burke (Consultant Supervisor) - Australian Institute of Sport
- Awarding institution
- University of the Sunshine Coast, Queensland
- Degree awarded
- Doctor of Philosophy
- DOI
- 10.25907/01115
- Organisation Unit
- School of Health
- Language
- English
- Record Identifier
- 991266296302621
- Output Type
- Dissertation
Metrics
22 File views/ downloads
14 Record Views