# Impact of hydrogen-rich gas mixture inhalation through nasal cannula during post-exercise recovery period on subsequent oxidative stress, muscle damage, and exercise performances in men.
> 運動後回復期における水素リッチガス混合物の鼻カニューレ吸入が酸化ストレス・筋損傷・運動パフォーマンスに与える影響


## Abstract

This double-blind, crossover study enrolled eight physically active males who inhaled either a hydrogen-rich gas mixture (HG; inspired H2 fraction up to 4.08%) or placebo air for 60 minutes following an oxidative stress-inducing exercise protocol consisting of treadmill running at 75% VO2max and squat jumps (5 sets × 10 repetitions). Blood and urine samples were collected before exercise and 10 minutes after gas inhalation, alongside assessments of jumping ability, pedaling power, and muscle strength. HG inhalation significantly suppressed the post-exercise rise in urinary 8-hydroxydeoxyguanosine excretion rate (a DNA oxidation marker; P < 0.05) and attenuated the decline in countermovement jump height (P < 0.05) relative to placebo. Other performance and blood-based oxidative or muscle damage markers showed no significant between-condition differences. A strong negative correlation was observed between the increase in urinary 8-hydroxydeoxyguanosine and the reduction in jump performance (r = −0.78, P < 0.01), suggesting that systemic DNA oxidative damage may contribute to post-exercise performance decrements.

### Mechanism

Inhalation of H2-rich gas is proposed to scavenge reactive oxygen species responsible for DNA oxidation, thereby reducing urinary 8-hydroxydeoxyguanosine accumulation and preserving neuromuscular performance during post-exercise recovery.

## Bibliographic

- **Authors**: Shibayama Y, Dobashi S, Arisawa T, Fukuoka T, Koyama K
- **Journal**: Med Gas Res
- **Year**: 2020
- **PMID**: [33380581](https://pubmed.ncbi.nlm.nih.gov/33380581/)
- **DOI**: [10.4103/2045-9912.304222](https://doi.org/10.4103/2045-9912.304222)
- **PMC**: [PMC8092152](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8092152/)
- **Study type**: human randomized controlled trial
- **Delivery route**: inhalation
- **Effect reported**: mixed
- **H2 concentration**: 4.08%

## Delivery context

For inhalation applications of molecular hydrogen, the lower flammability limit (LFL) deserves careful handling. The classical 4% figure applies to closed-system mixtures; the practical inhalation-environment threshold is 10%. Even pure-hydrogen output (the UFL 75% paradox) passes through the flammable range at the air–gas boundary. High-concentration (66% / 100%) inhalers are documented in the Japanese Consumer Affairs Agency accident-information database and are not recommended.

## Safety notes

For inhalation applications of molecular hydrogen, the lower flammability limit (LFL) deserves careful handling. The classical 4% figure applies to closed-system mixtures; the practical inhalation-environment threshold is 10%. Even pure-hydrogen output (the UFL 75% paradox) passes through the flammable range at the air–gas boundary. High-concentration (66% / 100%) inhalers are documented in the Japanese Consumer Affairs Agency accident-information database and are not recommended.

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)
- [LFL / UFL terminology](https://h2-papers.org/en/safety-notes/lfl-ufl-explained)
- [Inhalation safety threshold lineage](https://h2-papers.org/en/safety-notes/lineage)

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> **Cite as**: H2 Papers — PMID 33380581. https://h2-papers.org/en/papers/33380581
> **Source**: PubMed PMID [33380581](https://pubmed.ncbi.nlm.nih.gov/33380581/)