Effect of Pre-exercise Inhalation of Molecular Hydrogen on Metabolic Response During Graded Exercise in Healthy Women

The goal of this clinical trial is to evaluate if molecular hydrogen can reduce the metabolic response during graded exercise in healthy women aged 18-30 years. The main questions it aims to answer are: * Does molecular hydrogen reduce the respiratory exchange ratio? * Does molecular hydrogen reduce oxygen uptake? Researchers will compare molecular hydrogen to a placebo (ambient air containing no molecular hydrogen) to see if molecular hydrogen reduces the metabolic response. Participants will: * Inhale molecular hydrogen for 60 minutes each day for 7 days. * Undergo an exercise testing twice after a two-week washout period.

Inclusion Criteria: * Healthy female participants. * Regular menstrual cycle with exercise testing scheduled outside the menstrual phase. * Signed informed consent. Exclusion Criteria: * Pregnancy or breastfeeding. * History or presence of cardiovascular disease. * History or presence of respiratory disease. * Regular use of medications affecting metabolism. * Use of dietary supplements affecting metabolism within 14 days prior to intervention. * Strenuous physical activity within 24 hours prior to exercise testing. * Any contraindication to exercise testing or study participation determined by a physician.