Unravelling Energy Issues Underpinning Low Energy Availability in High Performance Athletes

The goal of this clinical trial is to understand how the body responds to short-term, severe low energy availability (LEA) in healthy, weight-bearing endurance athletes aged 18-45 years old. LEA describes a mismatch between an individual's dietary energy intake and the energy cost of their commitments for training and competition. The main questions this trial aims to answer are: 1. What effect does short-term, severe LEA have on sleeping metabolic rate? 2. What effect does short-term, severe LEA have on other body systems identified within the Relative Energy Deficiency in Sport (REDs) Health and Performance Conceptual models? Researchers will compare a control trial with both a LEA trial achieved through diet restriction and a LEA trial achieved through increased exercise to see if there are differences in the body's response. Participants will complete three 6-day trials, a minimum of 3-weeks apart, involving: * Prescribed diet (all food provided) * Prescribed running and/or cycling exercise * Two visits to ACU Fitzroy campus for blood tests and exercise testing * 50 hour stay (two nights and two days) in the ACU metabolic chamber

The study will involve a three-sequence crossover design, with participants undertaking a control trial first, involving energy availability of 40 kcal/kg fat free mass (FFM) and a 15 kcal/kg FFM exercise energy expenditure (EEE) as baseline training volume, before a counterbalanced allocation to low energy availability via dietary restriction (LEADIET) or low energy availability via increased exercise energy expenditure (LEAEX). This design will allow further screening of Relative Energy Deficiency in Sport (REDs) risk, identify participants who are likely to be unable to fulfil the exercise commitments of LEAEX and avoid the unknown carryover effects of two consecutive low energy availability (LEA) trials on the subsequent control trial, as would occur in some participants with a fully counterbalanced treatment allocation. Baseline testing (body composition/bone mineral density via DXA, aerobic capacity, LEA hormone blood panel, vitamin D, resting metabolic rate, REDs screening via REDs-CAT2) will be undertaken to confirm inclusion and develop individualised diet and training plans. Thereafter, participants will undertake a 6-day supervised exposure to energy availability of \~40 kcal/kg FFM/d, involving supplied meals and prescribed daily running/race walking. For female participants, trials will commence within days 1-5 of the menstrual cycle, to ensure that all testing occurs in the same (follicular) phase. A minimum 3-week washout period will occur between trials, with participants being guided to return to habitual training and dietary habits. Trials 2 and 3 will consist of exposure to severe LEA (15 kcal/kg FFM/d), which is achieved either by superimposing restricted energy intake (EI) or increased (doubled) EEE on the previous training plan. Diet plans and food provision will be managed by experienced sports dietitians to incorporate individual preferences and intolerances. While participants are free-living at the start of each trial week, food drops will be undertaken to check well-being and compliance to the diet/ training intervention. The final 2 days of residence at ACU facilities (medical unit and metabolic chamber) will allow more comprehensive data collection. Individual protocols (described briefly below) have been previously developed by our group and collaborators. Together, they will investigate within and between trial changes in metrics representing the range of body systems that have been identified at risk of perturbations due to LEA within the REDs Conceptual Health and Performance Models. Summary of the protocols completed in this study: 1. VO2 max: Running protocol: Measured once at screening visit (and potentially remeasured if participant trials are spaced \>3 months apart and aerobic fitness requires rechecking) 2. Resting Metabolic Rate: Outpatient protocol via Parvo metabolic cart: Measured once in baseline testing to enable calculation of EA components for intervention 3. DXA: total body composition: Measure Покажи пълното описание...

Inclusion Criteria: * 18-45 years old * Well trained weight-bearing athlete (tier 2-4 1) * Perform \~45km per week of weight-bearing endurance training, and able to undertake the prescribed exercise in each trial condition * Pass the ESSA pre-exercise screening tool and/or obtain GP clearance to exercise Exclusion Criteria: * Assessment of red status on the REDs Clinical Assessment Tool * Unable to attend ACU in Fitzroy, Victoria, for the 6 study visits for completion of the study protocol * Pregnancy * Use of hormonal contraceptive with the previous 3 months * Onset of peri/menopause