This study examines whether exposition to hyperbaric oxygen after a road-race simulation can help competitive cyclists recover and perform better the following day.

Hyperbaric oxygen, which involves breathing oxygen inside a pressurized chamber, is used as a recovery method in elite and professional sport. Its effectiveness, however, remains controversial: despite this widespread use, there is a lack of solid scientific evidence that a single HBO session after strenuous endurance exercise actually improves recovery, or that clarifies how the amount of oxygen exposure influences any benefit.

The study includes healthy male road cyclists between 18 and 40 years of age who compete at the national level in Belgium. After completing a fatiguing cycling session, each participant is randomly assigned to one of four groups receiving different levels of oxygen exposure during recovery.

Two groups breathe oxygen under increased pressure inside a chamber at either 2.5 or 1.4 atmospheres absolute. A third group breathes oxygen at normal pressure. The fourth group receives a sham condition that reproduces the treatment setting without active oxygen exposure.

The study is double-blind, meaning that neither the participants nor the researchers assessing the outcomes know which condition each participant receives.

The main goal is to determine whether a single session of post-exercise HBO improves next-day endurance performance, and whether higher oxygen exposure produces greater effects.

The researchers also collect blood samples and physiological measurements to better understand how the body recovers.

Inclusion Criteria:

• Road cyclists competing in Elite 2 (Elite without professional contract) or Under-23 (U23) categories or equivalent [Participation in national-level Belgian competitions within the previous 12 months. No specific ranking, finishing position, or performance threshold is required.]
• ≥ 2 consecutive years of cycling experience at regional or national level, with structured and periodized training
• Cycling-specific training volume ≥ 8 h a week over the preceding 10 weeks
• Stable training load in the weeks preceding inclusion, with no major changes due to injury, illness, or abnormal overload
• Measured VO₂max ≥ 60 ml/kg/min

Exclusion Criteria:

• Presence of significant cardiovascular, pulmonary, neurological, ENT, or metabolic disease, including but not limited to: Uncontrolled arterial hypertension (systolic blood pressure ≥ 180 mmHg and/or diastolic blood pressure ≥ 110 mmHg) ; Unstable heart disease or decompensated cardiomyopathy
• Contraindications to hyperbaric exposure, including: Untreated pneumothorax, History of spontaneous pneumothorax without medical clearance ; Pulmonary conditions associated with air trapping (e.g. emphysema or bullous lung disease), or abnormal thoracic imaging when indicated ; Recent thoracic surgery
• Neurological contraindications, including epilepsy, history of oxygen-induced seizures, or recent seizure activity, and any association with cannabis use
• Ear, sinus, or Eustachian tube disorders preventing adequate pressure equalization, including active infection or history of severe barotrauma
• Severe claustrophobia incompatible with chamber exposure