Abstract. The aim of this study was to evaluate the behaviour and relationships between hormones, and metabolic blood parameters essential for energetic balance control during rest, exercise and restitution. Two groups of young boys (17 cyclists and 11 canoeists) were tested twice. Tests were performed on a cycloergometer. During the first study, anaerobic threshold was determined by a non-invasive method and in the second one -cyclists performed prolonged 2-hour exercise below anaerobic threshold and canoeists -20-min effort above anaerobic threshold. Neuropeptide Y (NPY), leptin, insulin, C-peptide, metabolic clearance of insulin, growth hormone (GH), somatomedin C (IGF1) and glycaemia were analysed. Values of NPY and GH measured directly after exercise were significantly higher than the values of these parameters at rest, in both groups. However, effort did not cause significant changes in leptin concentration and insulin clearance in both groups. Besides, it was shown that 20-min exercise had no influence on insulin concentration in canoeists blood. In these studies significantly lower IGF1 value during restitution than directly after exercise was also noted in the cyclists group. Relations between measured hormonal parameters indicate that some mechanisms, which supply the organism with necessary energetic substrates during the effort, and accelerate the restitution are activated.(Biol.Sport 26:309-324, 2009)