This trial evaluates the effect of molecular hydrogen inhalation on metabolic response, heart rate, and rating of perceived exertion in healthy females during 30 minutes of exercise on a bicycle ergometer.

The objective of this randomized, double-blind, placebo-controlled crossover trial is to assess the effect of molecular hydrogen inhalation on metabolic response during 20 min of rest and during exercise on a bicycle ergometer with a workload of 0.5 W/kg for 10 min, 0.75 W/kg for 10 min, and 1 W/kg for 10 min. The trial recruits healthy females aged 20-35 years and the planned sample size is 20. The trial consists of two experimental sessions, one using molecular hydrogen inhalation and the other using placebo inhalation. The washout period between sessions is one week. Randomization of the order of the sessions is performed using a computer random generator. Molecular hydrogen is produced using a hydrogen generator via electrolysis of water and administered through a mouthpiece. Ambient air is used for placebo inhalation. Molecular hydrogen is colorless, odorless, and tasteless, making it indistinguishable from placebo by the human senses. During the session, the following variables are measured: ventilation, oxygen uptake, respiratory exchange ratio, heart rate, rating of perceived exertion, and oxygen saturation. Energy expenditure, fat oxidation rate and carbohydrates oxidation rate are calculated from oxygen uptake and respiratory exchange ratio. Statistical analysis is performed at the 0.05 significance level and data are evaluated using analysis of variance for repeated measures with Fisher's post hoc tests.

Inclusion Criteria:

• Free of major diseases.
• Signed informed consent.

Exclusion Criteria:

• Acute conditions contraindicating laboratory testing of exercise.
• Cardiorespiratory disease.
• Pharmacotherapy affecting metabolism.
• Musculoskeletal problems.

All IPD that underlie results in a publication.

Beginning 1 month after the publication of results with no end date.