An observational study in Physical Fitness, Athletic Performance and Body Composition, sponsored by Atlantica - Instituto Universitario. Active, not recruiting at 1 site in Portugal. Open to participants aged 18 Years to 65 Years. Per ClinicalTrials.gov, last updated 2026-10-14.
Sponsored by Atlantica - Instituto Universitario · Observational
HYROX© is a fast-growing fitness competition that combines long-distance running with functional exercises such as sled pushes, rowing, and weightlifting movements. Although the sport has attracted more than a million participants worldwide, little scientific research has looked at the health, body composition, and physical fitness of the people who compete in it.
This study will compare body composition, fitness, and performance between two groups of HYROX© participants: those competing at a recreational (amateur) level and those competing at an elite level.
Adult volunteers (ages 18-65) who train for or compete in HYROX© will be invited to take part. Researchers will measure body composition using a whole-body scan (DXA), skinfold thickness, and muscle ultrasound; resting metabolism; daily physical activity (using a wearable activity tracker); muscle strength and jumping ability; aerobic fitness (a treadmill running test); and short-burst power (a cycling test). Participants will also complete questionnaires about their motivation to exercise, their diet, and their use of dietary supplements, and will wear a heart rate monitor and activity tracker during an official HYROX© competition.
The results will help researchers, coaches, and athletes better understand how the bodies and training needs of HYROX© athletes differ by competitive level, which may support the development of safer and more effective training programs.
HYROX© is a standardized hybrid fitness competition, first held in 2017, combining 8 x 1 km runs with high-intensity functional stations (SkiErg, sled push/pull, burpee broad jumps, rowing, farmers carry, sandbag lunges, and wall balls) performed with minimal recovery between efforts. Despite its rapid global growth, peer-reviewed research characterizing the physiological, anthropometric, and performance profiles of HYROX© athletes remains scarce, and no prior study has compared these characteristics across competitive levels within this modality.
This is a single-center, cross-sectional study conducted at the Bettery® LifeLab, Atlântica - Instituto Universitário (Barcarena, Portugal), with an additional field-based assessment during an official HYROX© competition in Lisbon, Portugal. Participants will be classified as elite or recreational/amateur based on their relative finishing rank in official HYROX© events (top 15% of their division and age group for the elite group) and on training/competition history for the recreational group.
Laboratory assessments include: (1) body composition, evaluated through anthropometry (weight, height, 7-site skinfolds), dual-energy X-ray absorptiometry (DXA), and B-mode ultrasonography of the rectus femoris; (2) energy expenditure components, including resting metabolic rate by indirect calorimetry and habitual physical activity by accelerometry; (3) neuromuscular and performance tests, including handgrip strength, countermovement jump height, an incremental treadmill test to determine VO2max and maximal aerobic speed, and a supramaximal Wingate cycling test for anaerobic power; and (4) questionnaires assessing exercise motivation (BREQ-3), dietary intake (three-day food records reviewed by a registered dietitian), and dietary supplement use.
During an official HYROX© competition, participants will be equipped with their own heart rate monitors and with accelerometers to characterize external and internal load, finishing time, and, when available, station split times, together with pre- and during-event nutritional intake.
Based on an a priori sample size calculation (large effect size, d = 0.8, for the primary comparison of VO2peak between groups; alpha = 0.05; power = 80%), a target of 66 participants (33 per group) will be recruited to account for an anticipated 20% dropout rate. This characterization is intended to inform the development of training and preparation strategies tailored to athletes' competitive level within the HYROX© modality.
Atlantica - Instituto Universitario is the lead sponsor of 2 studies on the registry; none are open to participants now.
Counted across the registry records on this site, refreshed daily.
Adult men and women who train for or compete in HYROX©, a hybrid fitness competition combining distance running with functional exercise stations. Participants will be recruited on a voluntary basis via social media advertising and during an official HYROX© competition in Lisbon, Portugal, and classified into two groups: elite athletes (top 15% finishers in their division and age group) and recreational/amateur athletes (>6 months of HYROX© training experience).
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
No intervention
Maximal Oxygen Uptake (VO2peak)
Peak oxygen consumption (mL·kg-¹·min-¹), measured via breath-by-breath gas analysis during an incremental treadmill test to volitional exhaustion; compared between elite and recreational HYROX© athletes.
Time frame: Baseline (single laboratory assessment)
Body Composition (Fat Mass and Fat-Free Mass)
Total and regional fat mass and fat-free mass will be assessed using dual energy X-ray absorptiometry (DXA) (Hologic Horizon Wi, Waltham, USA). A whole-body scan will be performed according to the manufacter's guidelines. The attenuation of X-rays pulsed between 70 and 140 kV synchronously with the line frequency for each pixel of the scanned image will be measured.
Time frame: Baseline
Bone Mineral Density
Bone Mineral Density will be assessed using dual energy X-ray absorptiometry (DXA) (Hologic Horizon Wi, Waltham, USA). A whole-body scan will be performed according to the manufacter's guidelines (Park et al., 2002). The attenuation of X-rays pulsed between 70 and 140 kV synchronously with the line frequency for each pixel of the scanned image will be measured.
Time frame: Baseline
Resting Metabolic Rate
Resting Metabolic Rate (RMR) will be assessed using indirect calorimetry with a ventilated canopy open-circuit system (Quark, Cosmed, Italy). Participants will be instructed to arrive in a fasted state (at least 10 hours) and to refrain from exercise for 24 hours prior to their evaluation. At arrival, they will rest in a supine position in a quiet, temperature and humidity-controlled room with a blanket provided as an option. The equipment will be calibrated daily in accordance with the manufacturer's guidelines. Data will be collected for at least 15 minutes, with the initial 5 minutes discarded, following standard protocol. The average RMR (kcal/day) will be calculated based on the 5-minute period showing the lowest coefficient of variation.
Time frame: Baseline
Handgrip Strength
Maximal isometric handgrip strength of the dominant hand will be determined using a Jamar®hydraulic hand dynamometer (Jamar, Sammons Preston, Inc, Bolingbrook, IL). The participants will be tested in a standing position with an elbow in full extension. The participant will be asked to squeeze the dynamometer at maximal effort for three trials, with a 30-s break between each trial. The best of the three trials will be considered for data analysis.
Time frame: Baseline
Countermovement Jump Height
Jump height will be assessed by a countermovement jump which was performed on a contact-mat jump system controlled by an open-source hardware and software model (Chronojump, Barcelona, Spain). The best attempt out of three will be considered for analysis.
Time frame: Baseline
HYROX© Competition Finishing Time
Total race time and, when available, station split times
Time frame: Baseline
Plan to share: Undecided
No publications or documents are linked to this record.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is active, not recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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Atlantica - Instituto Universitario