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

Haute Ecole Bruxelles-Brabant23 enrolled

Overview

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

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

Eligibility

Sex: MALEMin age: 19 YearsMax age: 35 YearsHealthy volunteers:

Medical Language ↔ Plain English

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

Outcomes

Primary Outcomes

maximal oxygen uptake (VO₂max)

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.

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

Secondary Outcomes

the first and second ventilatory thresholds (VT1, VT2)

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.

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

peak blood lactate

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.

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

session rating of perceived exertion (RPE).

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.