AN ANALYSIS OF THE LEVEL OF FITNESS, PHYSICAL PERFORMANCE AND CONCENTRATION OF THE BRAIN-DERIVED NEUROTROPHIC FACTOR IN SALIVA IN ADOLESCENTS PRACTICING COMPETITIVE SPORTS AND THEIR PEERS

The purpose of the study was to compare BDNF in saliva before and after a maximum physical effort in adolescents practicing sports and their non-training peers, related to the body composition and physical fitness. The study comprised 64 individuals aged 13-14 (39 practicing sports). Physical fitness was measured using the EUROFIT test. The maximum oxygen uptake was determined on a mechanical treadmill. Saliva BDNF concentration was measured (R&D, USA) at rest and after an exercise. The research results prove that body composition was different depending on the sex, the EUROFIT results were not. The percentage of body fat correlated negatively with the strength of the lower body and the strength of the trunk muscles. There was a positive relationship between the muscle mass and the cardiorespiratory fitness, regardless of the level of training. BDNF in saliva was comparable in non-training and training individuals. BDNF was significantly dependent on the body composition only in girls and negatively correlated with the content of adipose tissue. Training and non-training teenagers did not differ in fitness, but in the level of cardiorespiratory fitness. Non-training teenagers showed a higher concentration of BDNF in saliva and further increase after the exercise stress test. In the training individuals, the exercise stress test did not lead to an increase in BDNF concentration.