Pool walking may temporarily improve renal function by suppressing renin-angiotensin-aldosterone system in pregnant women

Background This study aimed to examine the effect of pool walking on renal function in pregnant women. Methods Fifteen pregnant women (mean gestational age, 37.8 weeks) walked in a pool (depth 1.3 m) for 1 h. A few days later, they walked on a street for 1 h. Within each activity, the starting and ending levels of plasma renin activity (PRA) and serum aldosterone (SA) were compared using paired t-test. Total urine volume, creatinine clearance, and change in PRA levels between each activity were compared by t-test. Regression coefficients for total urine volume and creatinine clearance during pool walking were estimated by linear regression and additionally controlled for the change in PRA levels. Land walking served as the reference group. Results Within each activity, the renin-angiotensin-aldosterone levels were suppressed during pool walking: the mean starting and ending values of PRA and SA were 6.8 vs. 5.5 ng/mL/h (p=0.002) and 654 vs. 473 pg/mL (p=0.02), respectively. Compared to land walking, the decrease in PRA level was more evident in pool walking (−1.27 vs. 0.81 ng/mL/h, p=0.004), resulting in higher total urine volume and creatinine clearance in pool walking (both p<0.05). In regression analysis, after controlling for the change in PRA levels, the significantly elevated regression coefficients for total urine volume and creatinine clearance in pool walking were attenuated. Conclusions Pool walking may temporarily improve renal function in pregnant women, partly through the suppressed renin-angiotensin-aldosterone system. Clinical Trial Registration URL: [https://upload.umin.ac.jp/cgi-bin/ctr/ctr\_view\_reg.cgi?recptno=R000010618][1] Unique Identifier: UMIN000009051 [1]: https://upload.umin.ac.jp/cgi-bin/ctr/ctr_view_reg.cgi?recptno=R000010618