Completed

NCT Number: NCT07551869

Oxygen as a Metabolic Modulator: Divergent Physiological Adaptations to Hypoxic and Hyperoxic Tabata Training.

The purpose of this study is to examine how breathing air with different oxygen concentrations (higher or lower than normal) during high-intensity interval training affects:

* Aerobic capacity (VO₂max) * Ventilatory thresholds * Blood lactate levels * Perceived exertion This research aims to better understand how oxygen availability influences physiological adaptations to exercise.

If you agree to participate, you will undergo the following:

Baseline testing:

* Cardiopulmonary exercise test (cycling until exhaustion) * Measurement of oxygen consumption, heart rate, and ventilatory thresholds * Blood lactate measurement (finger prick)

Training intervention (3 weeks):

* 3 sessions per week (total of 9 sessions) * High-intensity interval training (Tabata protocol: 8 × 20 seconds effort / 10 seconds rest) * Exercise performed on an air-resistance cycle ergometer

During training, you will breathe either:

* Hyperoxic air (high oxygen concentration) or * Hypoxic air (low oxygen concentration) You will be randomly assigned to one of these conditions.

Post-intervention testing:

• Same assessments as baseline

The risks associated with this study are similar to those encountered during high-intensity exercise:

* Fatigue * Muscle soreness * Shortness of breath * Temporary discomfort from finger-prick blood sampling

Breathing altered oxygen concentrations (hypoxia or hyperoxia) may induce:

* Mild dizziness * Increased breathing effort (hypoxia) * Sensations of ease or altered effort perception (hyperoxia) All sessions are supervised by trained personnel, and safety monitoring is ensured throughout the study

You may benefit from:

* Improved physical fitness * Detailed physiological assessment (VO₂max, thresholds) However, no direct health benefit is guaranteed. Your participation is entirely voluntary. * You may withdraw at any time * You do not need to provide a reason * Withdrawal will not affect your academic or professional standing

All collected data will be:

* Anonymized * Stored securely * Used only for research purposes Your identity will not be disclosed in any publication. Data will be handled in accordance with applicable data protection regulations (GDPR).

You have the right to:

* Access your data * Request correction or deletion where applicable

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Key information

Conditions

Hyperoxia / High FiO₂ Exposure HIIT High Intensity Interval Training Hyperoxia Hypoxia Interval Training Pathological Conditions, Signs and Symptoms Signs and Symptoms Signs and Symptoms, Respiratory VO2max

Age range

19 year–35 year

Sex eligibility

Male

Study type

Interventional

Phase

Not applicable

Primary location

Haute Ecole Bruxelles Brabant - HE2B

Brussels, Brussels Capital, 1040, Belgium

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

recreationally active
male
18-35 years old

Exclusion criteria

engaged in professional or elite-level sports training
cardiovascular, pulmonary, metabolic, or neurological disease
taking medications known to influence cardiovascular or metabolic responses to exercise To minimize potential confounding factors, participants were instructed to refrain from strenuous physical activity, alcohol consumption, caffeine intake, and smoking for at least 24 hours before each testing session, in accordance with standard exercise testing procedures recommended in exercise physiology guidelines

Treatment and study plan

FIO2 modulation during HIIT protocol on assault bike

Other

Normobaric hyperoxic breathing during high-intensity interval training (FiO2 0.60) and hypoxic (FiO2 0.16)

Primary outcomes

maximal oxygen uptake (VO₂max)

Time frame: From enrollment to the end of protocol at 3 weeks

VO2max represents the maximal rate at which an individual can consume oxygen during incremental exercise. It is measured during a graded exercise test (e.g., treadmill or cycle ergometer) using indirect calorimetry. It reflects aerobic capacity and cardiovascular fitness. Higher values indicate better aerobic performance and endurance capacity.

Secondary outcomes

the first and second ventilatory thresholds (VT1, VT2)

Time frame: from enrollment to the end of the protocol at 3 weeks

VT1 (first ventilatory threshold) corresponds to the exercise intensity at which ventilation begins to increase disproportionately relative to oxygen uptake, indicating the onset of lactate accumulation. VT2 (second ventilatory threshold) marks a further disproportionate increase in ventilation due to metabolic acidosis. These thresholds are determined from gas exchange analysis during exercise testing and reflect submaximal aerobic and anaerobic transition points.
peak blood lactate

Time frame: from enrollment to the end of protocol at 3 weeks

Peak blood lactate is the highest concentration of lactate measured in the blood during or immediately after maximal exercise. It is assessed via capillary or venous blood sampling. This measure reflects the degree of anaerobic metabolism and glycolytic contribution during high-intensity effort.
session rating of perceived exertion (RPE).

Time frame: from enrollment to the end of the protocol at 3 weeks

RPE is a subjective measure of exercise intensity based on an individual's perception of effort, typically assessed using standardized scales such as the Borg scale (6-20 or 0-10). It integrates physiological and psychological responses to exercise and is useful for monitoring training load and tolerance.

Sponsors and collaborators

Lead sponsor

Haute Ecole Bruxelles-Brabant

Other

Registry information

Important dates

Study start: 2023
Primary completion: 2023
Study completion: 2025
First posted: Apr 27, 2026
Registry last updated: Apr 30, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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