We studied the effects of a twelve months endurance-training program on exercise-induced change in blood contents in thirteen rowers. A standardized testing-session (18 km rowing at 80 % of VO2max) was performed 19 times during the training program. Capillary blood samples were taken at rest and immediately post-exercise to analyse a wide range of serum concentrations. During exercise, glucose and lactate concentrations stabilized after only five training weeks and did not evolve from that point. Transport and hepatic protein concentrations increased with exercise up to the 15th week (p = 0.03), and remained stable from that point (p = 0.02). Evolution of exercise-induced change in alpha 1 -acid glycoprotein concentration revealed protein metabolism adaptations to training. Change in alpha 1 -acid glycoprotein concentrations were exactly opposite to that of urea and alpha 1 -antitrypsin (p = 0.01 and 0.002, respectively). Immunoglobulin concentrations exhibited important increases up to the 6th training week (p < 0.05), and a global stabilization was observed from that point. However, analysis of IgG subclasses highlighted significant changes that could not be found with the study of total IgG concentrations. Evolution of the exercise-induced change in Apo-A 1 /Apo-B concentrations ratio was also more informative about lipid metabolism than the Apo-A 1 and Apo-B concentrations taken individually. Indeed, evolution of metabolic changes during exercise should be carefully monitored during training to avoid interpretative errors on the training status of athlete.