Purpose: The purpose of this research was to examine the effects of high-intensity exercise (HIE) and steady-state exercise (SSE) on renal functions and plasma aldosterone.
Methods: Fifteen healthy men (age 18.67±0.62 years, body mass index [BMI] 21.16±1.80 kg·m-2, HR 56.33±9.16 bpm, and maximal oxygen consumption [ ] 47.39±1.34 ml·kg-1·min-1) participated in two exercises separated by 1 week. The first week, participants performed HIE that assigned them to run on a treadmill until exhaustion. In this test, the treadmill speed was set at 7.5 km·hr-1 in the first minute and was increased 0.5 km·hr-1 for every 30 seconds. The second week, participants performed SSE that assigned them to run for 60 minutes at 60% of the peak speed achieved during the HIE. Renal function indices and plasma aldosterone were measured pre-exercise and immediately and 30 minutes after exercise. Data were statistically analyzed using one-way analysis of variance with repeated-measures, Bonferroni method, and pair-sample t-tests. Statistical significance was accepted when p < 0.05.
Results: Compared to pre-exercise, HIE led to significant increase in plasma sodium (143.80±0.52 vs. 148.00±0.54 mEq·L-1, p < 0.001), osmolality (295.13±0.95 vs. 303.80±1.35 mOsm·kg-1, p < 0.001), and creatinine (1.06±0.03 vs. 1.09±0.03 mg·dl-1, p < 0.01) immediately after exercise, and in plasma sodium (145.20±0.58 mEq·L-1, p < 0.001) 30 minutes after exercise, while SSE resulted in significantly elevation in plasma aldosterone (17.49±4.56 vs. 53.07±8.23 ng·dl-1, p < 0.001), sodium 142.73±0.55 vs. 143.87±0.53 mEq·L-1, p < 0.001), osmolality (293.73±0.92 vs. 297.67±0.90 mOsm·kg-1, p < 0.001), and creatinine (1.11±0.03 vs. 1.19±0.04 mg·dl-1, p < 0.01) and urine creatinine (231.64±26.43 vs. 334.46±44.59 mg·dl-1, p < 0.01) immediately after exercise, and in plasma aldosterone (32.16±7.82 ng·dl-1, p < 0.05) and creatinine (1.17±0.04 mg·dl-1, p <0.01) and urine creatinine (376.28±42.49 mg·dl-1, p < 0.001) and osmolality (828.60±65.93 vs. 960.27±32.26 mOsm·kg-1, p < 0.05) 30 minutes after exercise. Compared to HIE, SSE led to higher increase in plasma aldosterone and creatinine and urine creatinine immediately after exercise (p < 0.05, 0.05, and 0.05, respectively), and in plasma creatinine and urine osmolality and creatinine 30 minutes after exercise (p < 0.05, 0.001, and 0.001, respectively).
Conclusion: The effects on renal functions and plasma aldosterone of SSE are greater than HIE. These effects are sustained during 30 minutes of recovery.