The impact of graded exercise to exhaustion on breath hydrogen: a pilot study

Abstract

Purpose Exercise induces transient physiological disruptions, including immune suppression and gastrointestinal (GI) disturbance. Molecular hydrogen (H₂), an endogenously produced gas with antioxidant and anti-inflammatory properties, may play a protective role in this context. While the therapeutic potential of exogenous H₂ has been widely explored, little is known about endogenous hydrogen responses to exercise. This study aimed to investigate post-exercise breath hydrogen kinetics as a potential indicator of metabolic and GI stress. Methods Thirty healthy young male athletes (age: 23.5 ± 3.8 years) completed an incremental running test to exhaustion. Breath hydrogen concentration was measured at baseline and at 5, 15, 30, 45, and 60 minutes post-exercise using an electrochemical fuel cell analyzer. The Friedman test with Bonferroni-corrected Wilcoxon post hoc comparisons was used to evaluate time-dependent changes. Results Breath hydrogen levels declined significantly at 5 minutes post-exercise (16.20 ± 16.22 ppm vs. baseline 36.37 ± 32.12 ppm; p 0.001), partially rebounded at 15 minutes (28.47 ± 33.76 ppm; p = 0.003), and approached baseline at 30 and 45 minutes. A secondary reduction was observed at 60 minutes (29.23 ± 36.55 ppm; p = 0.01). Significant deviations from baseline remained evident at multiple time points after correction. Conclusion This pilot study reveals a distinct post-exercise decline and delayed recovery in breath hydrogen concentrations, potentially reflecting impaired intestinal fermentation, increased oxidative stress, and altered redox homeostasis. Breath hydrogen may represent a novel, non-invasive biomarker of exerciseinduced physiological stress and recovery dynamics.

Study details

Article type

Original Research

Disease / injury model

Exercise-induced physiological stress (not a disease, but a physiological model)

Duration

1 days

Dose-dependent effect

No

Outcome

Neutral

Findings

Breath hydrogen levels significantly declined immediately after exhaustive exercise, partially rebounded, but remained below baseline for at least one hour, suggesting impaired intestinal fermentation, increased oxidative stress, and altered redox homeostasis. Breath hydrogen may serve as a novel, non-invasive biomarker of exercise-induced physiological stress and recovery.