Energy Availability and Its Impact in Elite Triathletes
For patients and families
In plain language
An automatic summary of structured registry data. It is an orientation aid, not a substitute for the official protocol or a physician assessment.
- What is being studied
- This is an observational study: the protocol does not assign a study treatment.
- Who it may be relevant to
- Registry conditions: Low Energy Availability, Relative Energy Deficiency in Sport. Basic parameters: from 18 years · All.
- What needs checking
- Age, condition and sex are only basic indicators. Prior treatment, laboratory values and other mandatory requirements appear in the eligibility criteria below.
- Where it takes place
- Denmark
- Next step
- Save the trial, show it to the treating physician, and confirm current recruitment with the study center. Costs, documents and travel →
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Official title
Energy Availability in Elite Triathletes: Impact on Performance and Injury Risk
Overview
This study investigates how energy availability affects performance, injury risk, and training outcomes in elite triathletes. Over two competitive seasons (2026-2027), 40 elite and sub-elite triathletes will be monitored through physiological tests, blood samples, and questionnaires. The goal is to identify markers of low energy availability and understand its impact on health and athletic performance. The study is observational and does not involve experimental treatments. Participants continue their regular training and diet while undergoing periodic assessments.
Detailed description
Low energy availability (LEA) is a condition where the energy intake of an athlete is insufficient to support both training demands and essential physiological functions. LEA is common among endurance athletes, including triathletes, due to high training volumes and sometimes intentional dietary restrictions. Prolonged LEA can lead to hormonal imbalances, impaired bone health, reduced immune function, and increased injury risk. This study aims to explore the prevalence and consequences of LEA in elite triathletes over two seasons.
The study is a 2-year exploratory cohort study conducted at the Institute of Sports Medicine, Bispebjerg Hospital, Copenhagen. Forty elite or sub-elite triathletes (men and women, aged 18+) who train more than 15 hours per week will be enrolled. Participants will undergo five comprehensive test days spaced across the off-season, pre-season, and in-season periods of 2025-2027. These test days include blood sampling, DXA scans, MR imaging, muscle strength and stiffness assessments, VO₂ max testing, and dietary and activity monitoring.
The primary outcome is the change in the thyroid hormone triiodothyronine (T3), a known marker of LEA. Secondary outcomes include bone density, muscle mass, metabolic rate, performance metrics (e.g., running economy, VO₂ max), and injury incidence. Energy availability will be assessed via validated questionnaires (LEAF-Q for females, LEAM-Q for males), dietary logs (MyFood24), and training data from wearable devices.
Monthly injury reports and quarterly dietary assessments will be collected. Blood samples will be analyzed for hormones (e.g., cortisol, testosterone, GH, IGF-1, TSH, T3, T4), bone turnover markers (CTX, PINP, osteocalcin), immune parameters, and nutritional status (e.g., vitamin D, iron, B12). Some samples will be stored in a coded biobank until 2029 for future analysis.
Participants will receive no financial compensation but will be reimbursed for public transport. All procedures are non-invasive or minimally invasive and carry low risk. The study has been approved by the relevant ethics committee (Approval No. H-25043062), and informed consent will be obtained from all participants.
Results will be published in peer-reviewed journals and presented at scientific conferences. If not accepted for publication, results will be made publicly available via ClinicalTrials.gov and the EU Clinical Trials Register.
Primary outcome measures
- T3 [Time frame: Two years - from off-season 2025 until in-season 2027]
Secondary outcome measures (12)
- RER [Time frame: Two years - from off-season 2025 until in-season 2027]
- Bone mineral density [Time frame: Two years - from off-season 2025 until in-season 2027]
- Fat free mass [Time frame: Two years - from off-season 2025 until in-season 2027]
- Appendicular fat free mass [Time frame: Two years - from off-season 2025 until in-season 2027]
- Fat mass [Time frame: Two years - from off-season 2025 until in-season 2027]
- Tendon thickness [Time frame: Two years - from off-season 2025 until in-season 2027]
- Tendon vascularisation [Time frame: Two years - from off-season 2025 until in-season 2027]
- Tendon stiffness [Time frame: Two years - from off-season 2025 until in-season 2027]
- Quadriceps muscle strength [Time frame: Two years - from off-season 2025 until in-season 2027]
- Hamstring muscle strength [Time frame: Two years - from off-season 2025 until in-season 2027]
- Peak muscle power [Time frame: Two years - from off-season 2025 until in-season 2027]
- Jump height [Time frame: Two years - from off-season 2025 until in-season 2027]
Eligibility criteria
Inclusion criteria
- Age ≥18 years
- Healthy individuals
- Training ≥15 hours/week in triathlon
Exclusion criteria
- Smokers
- Use of prohibited substances (WADA list) without medical justification
- Existing injuries or illnesses that could worsen due to participation
Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.
Healthy volunteers: Yes
Study design
- Observational model
- Cohort
Study locations
Denmark · 1 center
- Institute of Sports Medicine Copenhagen, Bispebjerg Hospital — Copenhagen
Identifiers
NCT: NCT07232628 · BBH171 · H-25043062