Sodium Balance, Fluid Homeostasis and the Renin–Aldosterone System during the Prolonged Exercise of Hill Walking

Abstract

1. The effect of 5 consecutive days of hill walking on electrolyte balance, fluid homeostasis, plasma renin activity and plasma aldosterone concentration was studied in five male subjects. 2. The 5-day exercise period was preceded by a 4-day control period and followed by a 4-day recovery period. Throughout the 13-day study subjects ate a fixed diet. 3. After 5 days of exercise subjects had retained a mean of 264 mmol (SD 85) of sodium. Plasma sodium concentration remained constant at 142.0 mmol/l (SD 5.4). This indicates an expansion of the extracellular space by 1.84 litres. 4. By the end of the exercise period there was a positive water balance of about 0.9 litre. Thus there was a net movement of 0.94 litre of fluid from the intracellular to the extracellular space. 5. Packed cell volume decreased from a mean of 43.5% to 37.9% after 5 days of exercise, indicating that about 0.9 litre of the extracellular fluid entered the vascular compartment. The remaining fluid may be responsible for the significant increase in lower leg volume. 6. During the exercise period plasma aldosterone concentration and plasma renin activity rose, and there was a highly significant correlation between these values and the sodium retention. There was also a significant correlation between sodium retention and the increase in leg volume, which suggests that oedema may be the result of prolonged exercise of this type.

Renin–Angiotensin–Aldosterone System Is Not Involved in the Arterial Stiffening Induced by Acute and Prolonged Exposure to High Altitude

“…37,38 The behavior of RAAS during exposure to HA has been extensively described in previous works because changes in this system induced by hypoxia and physical efforts can lead to alterations in sodium and fluid balance which, in turn, can favor the occurrence of acute mountain sickness. This possibility was suggested by the demonstration that prolonged exercise at SL results in sodium retention and peripheral edema because of the activation of RAAS, 39 leading to hypothesize that also sustained exercise at HA might induce a similar fluid gain after a similar activation of RAAS. 40 The effect of hypobaric hypoxia on plasma renin activity and plasma aldosterone concentrations may depend on the time spent at HA, on the altitude level, and on the physical activity degree.…”

Body Composition, Energy, and Fluid Turnover in a Five-Day Multistage Ultratriathlon: A Case Study

“…We found an increased concentration of sodium post race and an increase of PV ( Figure 5). Transient expansion of PV is commonly reported after endurance events (Fellmann et al 1999;Milledge et al 1982). Prolonged exercise in the heat causes increased loss of TBW by sweating and respiration.…”

“…The reaction of the hormones was interpreted to favour a relative fluid consumption. In another study, five consecutive days of hill walking led to a retention of sodium leading to an expansion of the extracellular space (Milledge et al 1982).…”

Effect of a Multistage Ultraendurance Triathlon on Aldosterone, Vasopressin, Extracellular Water and Urine Electrolytes

“…9,10 It has been well documented that prolonged strenuous exercise over several consecutive days induced a progressive increase in extracellular water, plasma volume and total body water. [11][12][13][14][15] Sodium retention seemed to be the major factor in the increase in plasma volume. 9 In multi-stage ultra-endurance runs, plasma volume increased, 13-15 plasma [Na + ] concentration was maintained 15,16 and aldosterone increased.…”

“…9 In multi-stage ultra-endurance runs, plasma volume increased, 13-15 plasma [Na + ] concentration was maintained 15,16 and aldosterone increased. 13,14 Presumably fluid homeostasis during an ultra-endurance performance is regulated by both aldosterone and vasopressin.…”