Marathon racing is a strenuous exercise that has a profound effect on many laboratory parameters. Participants in marathon races may require abstinence of exercise and the performance of laboratory assays several days after the event. The aim of this study was to evaluate the possible changes in blood cell count and biochemical parameters observed in participants in a marathon 3 days before and 3 days after and before and immediately after a cardiopulmonary exercise test. Incremental cycle ergometry up to maximal capacity was performed in 7 marathon runners, 3 days before and 3 days after the race. The % peak oxygen consumption (peak %VO2) achieved was statistically significantly lower after than before the race (p = 0.02). No statistically significant differences were observed in cardiac frequency (p = 0.148) or blood cell count (p = 0.501). Also, the concentration of sodium, potassium, calcium, magnesium, lactate dehydrogenase (LDH), phosphocreatine kinase (CPK) and glucose, measured before and immediately after the pulmonary exercise test, did not differ significantly (p < 0.5). A significant percentage of the laboratory results were outside the standard reference rates. According to our data, exercise performance, as expressed by peak %VO2, continued to be decreased in marathon runners 3 days after the race. The blood cell count and biochemical parameters did not differ significantly but many marathon runners were outside the standard reference rates. Unfortunately, only 7 subjects were available for this study. Further studies with larger samples and with samples obtained at multiple times during and after exercise are needed to clarify the effects of long-distance running.
