Effects of exercise on renal function in patients with moderate impairment of renal function compared to normal men.

The renal excretory and haemodynamic responses to sustained moderate exertion were investigated in normotensive humans with impaired renal function and normal volunteers. The heart rate increase with exercise was similar in each group. Subjects with impaired renal function showed a significant fall in glomerular filtration rate on exertion, while normals did not. In the presence of renal disease, urine osmolality did not rise with exertion, although it rose markedly in the normal group. Free water clearance became negative after exercise in the normal group only. The diseased kidney is unable to maintain glomerular filtration rate or conserve water under the stress of exertion as well as the normal kidney.