Urea and Creatinine Production and Excretion in Urine during and after Prolonged Heavy Exercise

Abstract

Serum and urine creatinine and urea were determined in well-trained men for several days in connection with three long-distance cross-country ski races (70–90 km). The races led to about 60 per cent increase in serum creatinine and urea, the return to the pre-race level being rapid for creatinine and taking several days for urea. The average race creatinine and urea production rates were about 60–80 per cent higher than under resting conditions, whereas the race urinary excretion was about the same as that at rest for creatinine but was markedly reduced for urea. The race urea production, the changes in serum urea and creatinine, as well as the time taken for the serum changes to return to pre-race levels rose with increasing age, whereas the race urine flow and clearance of urea and particularly of creatinine fell with age. One case, in which acute oliguric renal failure developed after a 90-km race, is included in an addendum to the report. It is concluded that the increase in serum creatinine after prolonged heavy exercise is due to increase in production and a lesser than proportional increase or even a decreease in urinary excretion, whereas the increase in serum urea is mainly due to decrease in excretion and, to a lesser extent, to increase in production; the deficiency of the kidneys to meet the excretory requirements increases with age.

Key Words:

• Anuria
• creatinine
• exercise
• metabolism
• renal function
• serum
• urea
• urine