Renal osmol clearance during prolonged heavy exercise

Abstract

Serum and urine osmolality and creatinine were measured in fifty-eight well-trained men, aged 21-57 years, in connection with three 70 km cross-country ski races, taking place under essentially the same external circumstances, leading to slight dehydration. Although the race urine flow was low, 0.51 (0.05-1.10) ml/ min, the urine osmolality and the urine to serum osmolality ratio were relatively low, averaging 860 (399-1220) mosm/kg H₂O and 2.84 (1.32-4.10), respectively. Decreasing urine flow and endogenous creatinine clearance were associated with decreasing urine to serum osmolality ratio, indicating declining urine concentrating ability. Thus, the data confirm the author's recent suggestion, based on the measurement of a limited number of urine solutes, that during prolonged heavy exercise a decrease in urine flow and glomerular filtration rate is accompanied by a decline in the urine concentrating ability.

Key Words:

• creatinine
• exercise
• glomerular filtration
• osmol clearance
• osmolality
• renal concentrating ability
• renal function
• urine