title: Relationship between urine flow, glomerular filtration, and urine solute concentrations during prolonged heavy exercise.
abstract: Serum and urine electrolytes, creatinine, and urea were determined in 21 well-trained men, aged 21-56 years, in connection with a 70-km cross-country ski race, lasting 4.39-6.52 h, leading to slight dehydration. Although the race urine flow was low, averaging 0.41 (0.1-0.9) ml/min, the average urine concentrations of urea, Na, Ca, Mg, Cl and P were markedly lower than during the preceding night, while the concentrations of K and creatinine were higher, the total of measured solutes being 621 nmol/l, compared with 911 nmol/l during the preceding night. Decreasing urine flow and endogenous creatinine clearance were accompanied by a falling urine solute concentration, particularly when the race creatinine clearance decreased to below 70 ml/min, mainly due to a fall in the urea, Na, and Cl concentrations. Thus, a decrease in the glomerular filtration rate was accompanied by a progressive decline in the urine concentrating ability.
mesh_terms: D000328:Adult; D002118:Calcium / Q000652:urine; D002712:Chlorides / Q000652:urine; D003404:Creatinine / Q000097:blood / Q000652:urine*; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000502:physiology*; D007671:Kidney Concentrating Ability; D008274:Magnesium / Q000652:urine; D008297:Male; D008875:Middle Aged; D009318:Natriuresis; D009994:Osmolar Concentration; D010758:Phosphorus / Q000652:urine; D005082:Physical Exertion; D011188:Potassium / Q000652:urine; D012865:Skiing; D012964:Sodium / Q000652:urine; D014508:Urea / Q000097:blood / Q000652:urine*
chemical_list: D002712:Chlorides; D010758:Phosphorus; D014508:Urea; D012964:Sodium; D003404:Creatinine; D008274:Magnesium; D011188:Potassium; D002118:Calcium