Study aims to verify the hypothesis:

• N-acetylcysteine (NAC) supplementation improves exercise capacity in people training endurance sports and the effectiveness of this supplementation depends on the polymorphism of genes related to folate and glutathione metabolism.
• NAC supplementation affects the parameters of oxidative stress among women and men training endurance disciplines

• Glutathione depletion caused by a combination of intense physical exertion associated with the generation of significant amounts of reactive oxygen species (ROS), and possibly with having an unfavorable variant of the methylenetetrahydrofolate reductase (MTHFR), glutamate-cysteine ligase catalytic subunit (GCLC); glutamate-cysteine ligase modifier subunit (GCLM); glutathione S-transferase Pi 1 (GSTP1); glutathione synthetase (GSS) or cystathionine-β-synthase (CBS) genes may contribute to lower adaptation to exercise, but also to deterioration of health of people training endurance sports.
• The main objective of the study is to verify the hypothesis that NAC supplementation has a beneficial effect on regeneration between intense exercise tests simulating a race characteristic for a given discipline. In addition, this study is aimed at checking whether genotype may modify the effectiveness of the supplementation measured as exercise and biochemical parameters . A double-blind study involving 100 women and men supplementing 1200 mg of N-acetylcysteine daily or 1200 mg of rice flour in three equal doses. Supplementation will last for 7 days. Blood sampling and body composition testing will be performed in the morning of the exercise test day. Discipline-specific exercise testing will be performed before and after the intervention.

Inclusion Criteria:

• Consent to participate in the study and acceptance of the established scheme for conducting the intervention
• age range between 18 and 45 years old
• regular training with a frequency of at least 3 times a week during the last year,

Exclusion Criteria:

• no consent to participate in the study and no acceptance of the established scheme of the conducted intervention
• existing diseases of the blood system and neoplastic diseases
• respiratory system diseases
• obesity
• any medical contraindications to exercise
• Results obtained from exercise tests that do not meet the inclusion criteria
• use of NAC during the last month
• allergy to NAC
• smoking
• pregnancy and lactation

Double (Participant/investigator)