The Impact of Exercise / Stress Stimuli on HMB Supplementation Efficacy

Inclusion Criteria: * written informed consent from all participants before the study * a current medical clearance to practice sports, * Group S: regular physical activity (\> 250 minutes per week), training practice (\> 10 years), * Group W: a subjects characterized by lack of regular physical activity that never were trained in competitive sports and certain features of malnutrition/low physical fitness, Exclusion Criteria: * current injury, * any health-related contraindication, * declared general feeling of being unwell, * unwilling to follow the study protocol, * serious disease or metabolic problems, * intake of ergogenic supplements 3 months before the beginning of the study, * history of anabolic androgenic steroids or drugs use that may interfere with muscle mass control (eg, corticosteroids), or affect physical performance, * smoking and tobacco use, * presence of infectious disease in the previous 4 weeks of the study