The Effect Of An Active Versus Inactive Lifestyle On Renal Response To Exercise-induced Dehydration

Abstract

PURPOSE: Exercise by itself as well as exercise-induced dehydration cause a decrease in renal blood flow and an increase in glomerular permeability, leading to a decrement in renal function and temporarily renal damage. An active lifestyle may precondition the kidneys, resulting in attenuated decrease in kidney function and a reduction in kidney damage in response to exercise and dehydration determined as body weight loss. Therefore, we examined the differences in renal responses to exercise-induced dehydration between healthy young men with a physically active versus inactive lifestyle. METHODS: A total of 12 active and 6 inactive healthy male participants (23±3 years, 23.9±3.6 kg/m2, eGFR: 111.0±12.5 mL/min) were included, based on a physical activity questionnaire. Participants performed an incremental exercise test to determine physical fitness and maximum heart rate (HRmax). On a separate day, a submaximal exercise test was performed on 80% of the individual HRmax, until 3% dehydration. Blood and urine samples were taken pre- and post-exercise to assess renal function (estimated glomerular filtration ratio; eGFR) and renal damage (urinary albumin). RESULTS: Maximum oxygen uptake (VO2max) was higher in the active (59.7±8.6 mL/min/kg) compared to the inactive group (49.1±7.3 mL/min/kg; p=0.018). All subjects cycled on a comparable exercise intensity (79±2% HRmax), resulting in a body mass loss of 3.2±0.7% and 2.5±0.4% for the active and inactive group, respectively (p=0.013). After exercise, a significant decrease in eGFR was found for the active (17.4±10.2 mL/min; p=0.007) and inactive group (21.7±17.8 mL/min; p=0.05), which did not differ between groups (p=0.60). Moreover, 33.3% of the active subjects and 50% of the inactive subjects had a post-exercise eGFR<90 mL/min, which indicates a decrease in renal function. Furthermore, we found a significant increase in urinary albumin concentration in the active (24.6±30.9 mg/L; p=0.011) and inactive group (33.6±27.5 mg/L; p=0.016), which did not differ between groups (p=0.55). CONCLUSION: In short, exercise induces a decrease in renal function and an increase in urinary albumin concentration, suggesting temporary renal damage of the glomerulus or proximal tubulus. However, these changes do not differ between physically active and inactive subjects.