Renal function in endurance trained volunteers during prolonged restriction of muscular activity

It has been demonstrated that changes in the functional status of the kidneys are basically responsible for the impaired fluid-electrolyte metabolism in physically healthy volunteers during hypokinesia (decreased number of walking steps/day). Thus, the objective of this investigation was to determine the functional changes of the kidneys of 20 endurance trained male volunteers aged 23 to 26 years with an average maximum oxygen uptake 65 ml.kg-1.min-1 during 364 days of hypokinesia (HK). All volunteers were on 14.6 km/day (10,000 running steps/day) prior to their exposure to HK. All volunteers were randomly assigned to one of the two groups: Ten volunteers were placed continuously under 14.6 km/day (10,000 running steps/day) (control subjects) and ten to 2.9 km/day (3,000 walking steps/day) (hypokinetic subjects). During the prehypokinetic period of 60 days and during the hypokinetic period of 364 days urinary and plasma electrolytes, glomerular filtration rate (GFR), renal plasma flow (RPF), were determined and isotope renographic tests were performed. The hypokinetic volunteers displayed a significant increase in urinary and plasma concentrations of electrolytes, a significant decrease in glomerular filtration rate and renal plasma flow, incorporation of isotope in the kidneys increased significantly while elimination of 131I-Hippuran from blood and kidneys decreased significantly. It is concluded that prolonged restriction of muscular activity induces significant changes in the examined renographic parameters of endurance trained volunteers which may be related to abnormalities of renal pelvis function or calyceal function.