Abstract

Male interscholastic swimmers (n = 8) completed a 4572 m training swim in 62 +/- 1.1 min with terminal heart rate and blood lactate of 152 +/- 6 beats/min and 6.9 +/- 0.89 mM, respectively. Sweat rate (0.48 +/- 0.095 l/h) was lower than similar intensity cycling (1.5 +/- 0.13 l/h) or running (1.1 +/- 0.14 l/h). Post-swim serum urea N (11.6 +/- 0.71 mM) was elevated vs pre-swim (4.6 +/- 0.39 mM). Post-swim urine volume (860 +/- 75 ml/24 h) was reduced and resulted in an elevated, but delayed (24-84 h), post-exercise urea N excretion. Although the reduced urine and sweat production during the swim undoubtedly contributed to the elevated serum urea, there must be another explanation because together they could only account for 38 of the observed increase. On the basis of the magnitude of serum urea increase, it appears that the swim caused an increase in urea production (amino acid oxidation). The failure to observe larger increases in urinary urea during recovery indicates that either urea excretion following exercise continues for prolonged periods of time (> 48 h) or another significant mode of nitrogen excretion exists. Verf.-Referat