Plasma atrial natriuretic peptide in elite runners.

Plasma atrial natriuretic peptide (ANP) was measured in relation to a 5-km race in 11 elite mid- and long-distance runners. Plasma ANP, measured in relation to the race, was compared with the relative changes in plasma volume and the physical fitness of the runners. Relative changes in plasma volume were estimated by changes in hemoglobin and hematocrit, and physical fitness was evaluated by a cycle ergometer test, running time, and resting heart-rate. In connection with the race, plasma ANP increased in all the runners. Median plasma ANP was 4.7 pmol.l-1 before the race and 12.9 pmol.l-1 immediately after the race. No correlation was found between the changes in ANP and the relative changes in plasma volume or the measurements of physical fitness. A volume expansion of the red blood cells was found immediately after the race. We conclude that well-conditioned subjects have a prominent rise in plasma ANP, in spite of a high maximal cardiac output.