Can Training with Extra Oxygen Make Athletes Faster?
Yes. In this crossover trial, athletes who trained while breathing 60% oxygen improved their performance time at 90% VO2max more than when they trained on room air. The extra oxygen let them hold their target heart rate at 8.1% higher power output.
Researchers wanted to test a simple idea. If athletes can work harder while breathing extra oxygen, could training at those higher intensities produce better results? This study put that theory to the test with a crossover design in which each athlete served as their own control.
What the Data Show
- Performance at 90% VO2max: increased after both hyperoxic and normoxic training, with the hyperoxic gain larger
- Training intensity advantage: 8.1% higher power output was required to hold the target heart rate while breathing 60% oxygen
- VO2max: trended higher after hyperoxic training, but the difference between conditions was not significant
- Maximum heart rate: unchanged after either training condition
- Training protocol: 10 intervals of 4 minutes at 90% max heart rate, 2 minutes rest between intervals, 1 hour a day, 3 days a week for 6 weeks
- Sample size: 9 athletes
Dr. Kumar’s Take
This study extends the logic of altitude training in the opposite direction. Instead of manipulating oxygen to make the work harder, it enriches oxygen so the athlete can do more work at the same cardiovascular cost.
The mechanism is the interesting part to me. The hyperoxic condition was not simply “more oxygen during exercise.” Because heart rate was the variable being held constant, the athletes had to push a higher power output to reach that target. That is the overload principle in action, delivered through a back door. More work went in, and more performance came out.
Cardiorespiratory responses at submaximal exercise improved similarly in both conditions, and maximum heart rate did not change in either.
I would hold this loosely. Nine athletes is a small sample, and the VO2max difference did not reach significance. The performance signal is real in this dataset, but it needs replication before I would build a training programme around it.
Study Design
Researchers used a single-blind crossover design. Nine athletes completed two 6-week training programmes on a cycle ergometer, separated by 12 weeks of detraining.
Subjects were randomly assigned to breathe either 60% oxygen or 21% oxygen during the first training block. For the second block, the breathing conditions were reversed, so every athlete completed both conditions.
Both conditions used the same target: 90% of maximum heart rate, 3 days a week, 1 hour a day, for six weeks. Each session consisted of 10 intervals lasting 4 minutes, with 2 minutes rest between intervals. Power output was adjusted during sessions to keep subjects inside the target heart rate range.
All pre- and post-training testing was carried out in normoxia, so the measured gains reflect training adaptation rather than an acute oxygen effect during the test itself.
Key Finding: Higher Training Intensity
The crucial difference was how much work subjects could do while maintaining their target heart rate.
When breathing 60% oxygen, subjects needed 8.1% higher power output to reach the same heart rate as when breathing normal air. Over the 6-week training period, this meant consistently training at a higher absolute workload for the same cardiovascular signal.
That gap is the whole intervention. Heart rate was pinned, so the oxygen showed up as extra watts.
Performance Results
After training, subjects were tested under normoxic conditions to see how much they had improved. The test measured how long they could cycle at 90% of VO2max.
Performance time increased after both training conditions. The increase after hyperoxic training was greater than the increase after normoxic training.
VO2max showed a trend toward a greater increase after hyperoxic training, but that difference did not reach statistical significance.
Why the Difference?
Cardiorespiratory responses were similar between the two conditions. Heart rate and ventilation during steady-state exercise at 80% VO2max both decreased after training, with no difference between the hyperoxic and normoxic conditions. Maximum heart rate did not change in either condition.
Because cardiorespiratory responses were similar, the authors suggest the performance advantage may be due to peripheral factors.
Direct measurement of muscle adaptation would be needed to confirm that, but the pattern fits the overload principle. The hyperoxic condition delivered more training work, and more training work produced more performance.
Practical Takeaways
- Breathing 60% oxygen allowed a higher power output at the same training heart rate
- That higher training intensity produced a greater improvement in performance time at 90% VO2max
- The advantage appears to come from peripheral factors, since cardiorespiratory responses were similar between conditions
- VO2max did not differ significantly between the two conditions
- Findings apply to high-intensity interval training at 90% of maximum heart rate in trained athletes
Related Studies and Research
- Optimal type and dose of hypoxic training for improving maximal aerobic capacity in athletes: a systematic review and Bayesian model-based network meta-analysis
- Advances in hyperbaric oxygen to promote immunotherapy through modulation of the tumor microenvironment
- Normobaric oxygen treatment for mild-to-moderate depression: a randomized, double-blind, proof-of-concept trial
- Hypoxia and Inflammation
FAQs
Why didn’t VO2max improve more with hyperoxia?
There was a trend toward a greater VO2max increase after hyperoxic training, but the difference between conditions was not statistically significant. VO2max depends heavily on central oxygen delivery, and both conditions trained at the same relative heart rate, so the cardiovascular stimulus was comparable. The performance difference is better explained by peripheral factors.
Was the study blinded?
It used a single-blind design, meaning the subjects were not told which gas they were breathing. Because it was also a crossover, each athlete completed both the hyperoxic and the normoxic block, which removes the between-subject variation that would otherwise muddy a nine-person trial.
Can recreational athletes use this approach?
The gas delivery equipment required to breathe 60% oxygen through a training session is not something most recreational athletes have access to. The transferable insight is the mechanism: the gains tracked training intensity, not the oxygen itself. If you can raise the work you complete in a session, that is the lever this study is pulling.
How does this relate to altitude training?
Altitude training manipulates oxygen availability downward, typically to drive adaptations to reduced oxygen. This study moves oxygen in the opposite direction, raising the inspired fraction to 60% so that a given heart rate corresponds to a higher power output. The two approaches target training intensity from opposite ends.
Bottom Line
Training while breathing 60% oxygen produced a greater improvement in performance time at 90% VO2max than training on room air, in a nine-athlete crossover trial with all testing conducted in normoxia. The mechanism is straightforward: holding heart rate constant while breathing enriched oxygen required 8.1% more power output, so the hyperoxic block delivered more training work. Cardiorespiratory responses were similar between conditions, which points to peripheral rather than central adaptation. The sample is small and the VO2max difference did not reach significance, so I read this as a well-designed proof of principle about training intensity rather than a finished protocol.
