Precise control of fluid and electrolyte homeostasis is essential for the survival of man. The performance of exercise results in a significant disturbance of water and electrolyte homeostasis. These alterations during exercise are due to the loss of fluids and electrolytes primarily in sweat and to voluntary dehydration associated with an inappropriate suppression of thirst. During the performance of exercise, as well as during recovery, compensatory measures occur to rectify these changes. A variety of hormones are important in the compensatory responses to correct water and electrolyte disturbances. The goal of this chapter is to describe the changes in water and electrolyte homeostasis resulting from exercise and the responses, regulation, and actions of the hormones important in correcting these imbalances.

Fluid and Electrolyte Homeostasis During and Following Exercise: Hormonal and Non-Hormonal Factors

The aim of this systematic review and meta-analysis was to evaluate the effect of exercise training on parameters of the renin–angiotensin–aldosterone system (RAAS) in healthy adults, and to investigate the relation with training induced changes in blood pressure. A systematic search was conducted and we included randomized controlled trials lasting ⩾4 weeks investigating the effects of exercise on parameters of the RAAS in healthy adults (age ⩾18 years) and published in a peer-reviewed journal up to December 2013. Fixed effects models were used and data are reported as weighted means and 95% confidence limits (CL). Eleven randomized controlled trials with a total of 375 individuals were included. Plasma renin activity was reduced after exercise training (n= 7 trials, standardized mean difference −0.25 (95% CL −0.5 to −0.001), P=0.049), whereas no effect was observed on serum aldosterone ((n= 3 trials; standardized mean difference −0.79 (−1.97 to +0.39)) or angiotensin II (n=3 trials; standardized mean difference −0.16 (−0.61 to +0.30). Significant reductions in systolic blood pressure −5.65 mm Hg (−8.12 to −3.17) and diastolic blood pressure −3.64 mm Hg (−5.4 to −1.91) following exercise training were observed. No relation was found between net changes in plasma renin activity and net changes in blood pressure (P>0.05). To conclude, although we observed a significant reduction in plasma renin activity following exercise training this was not related to the observed blood pressure reduction. Given the small number of studies and small sample sizes, larger well-controlled randomized studies are required to confirm our results and to investigate the potential role of the RAAS in the observed improvements in blood pressure following exercise training.

Effect of exercise training on the renin–angiotensin–aldosterone system in healthy individuals: a systematic review and meta-analysis

To study the relationship between plasma renin activity (PRA) and coffee consumption, cigarette smoking, alcohol intake and physical activity habits. Setting: The multicentre HARVEST trial, involving 17 Hospital Centres in Northeast Italy. Subjects: 351 borderline to mild hypertensive men (mean age ± SEM 22.7 ± 0.47 years), never treated for hypertension. Interventions: Office and 24-hour blood pressure measurement, supine and standing PRA levels, and urinary catecholamines output. Main outcome measures: PRA levels according to coffee intake and physical activity status. Results: Coffee intake showed a major effect on PRA. Supine PRA levels were 40% higher in the subjects abstaining from coffee (n = 94) than in the coffee drinkers and was similar in the moderate (n = 223) and heavy (n = 34) drinkers. A weaker negative association was found between coffee use and PRA on standing. Office and whole-day blood pressure and heart rate, and urinary catecholamines did not differ according to coffee intake. Supine PRA was lower in the subjects performing regular physical activity than in the inactive subjects. Office and whole-day diastolic blood pressure and heart rate, and urinary norepinephrine were lower in the active than in the sedentary men. No relationship was found between PRA measured either in the supine or the upright posture and tobacco or alcohol use. In a multiple linear regression model supine PRA was negatively correlated with age, coffee consumption and physical activity habits. Conclusions: Chronic coffee intake and physical training showed an inverse relationship with PRA in mild hypertensive men, while tobacco and alcohol use were unrelated to PRA.

https://www.jstor.org/stable/info/3581662

Relationship of plasma renin activity with caffeine intake and physical training in mild hypertensive men

The influence of treadmill or swimming exercise on resting values of plasma and brain arginine vasopressin (AVP), and plasma sodium, potassium, osmolality and proteins was studied after 5 weeks of training using female Wistar rats. The duration of daily training sessions was progressively increased to reach 6 h/ day for swim training (S) and 3 h/day for treadmill running (T). Compared to their untrained controls, treadmill and swim training were respectively associated with: 1. a significant lower body weight; 2. a decreased plasma AVP (36.4% for T and 47.4% for S) and hypothalamic AVP (20% for T and 16% for S); 3. a higher hypophyseal AVP (145% for T and 36.3 for S); 4. a decreased plasma osmolality (6.7% for T and 6.1% for S), sodium (1.2% for both) and potassium. (15% for T and 22.4% for S); and 5. no change in protein concentration. For T, rectal temperature increased (38.5±0.20 to 39.7±0.5) and for S rectal temperature decreased from 38.6±0.12 to 37.74±0.10).

Effects of treadmill running and swimming on plasma and brain vasopressin levels in rats

Eighteen patients with ischaemic heart disease were trained for 3 months, three times a week. The effectiveness of the training programme was demonstrated by increases of 27% in peak oxygen uptake and 29% in exercise duration, and by a decrease in resting and submaximal heart rates. Blood pressure, however, was not significantly affected during the training period. At rest and at submaximal exercise plasma renin activity (PRA) was lower after training. Plasma angiotensin I concentration (PA I) and angiotensin II concentration (PA II) were not significantly affected. Plasma aldosterone concentration (PAC), only measured at rest, was not significantly changed after the training period, while plasma norepinephrine (PNE) and epinephrine (PE) concentrations were significantly decreased, but only at high levels of exercise. A reduced sympathetic tone after training, suggested by the lower heart rates and the tendency to a decrease in PNE, is a likely explanation for the decrease in PRA. However, despite this decrease, PA I, PA II, and PAC were not significantly changed after training; the reason for this disrepancy is unknown.

Influence of physical training on blood pressure, plasma renin, angiotensin and catecholamines in patients with ischaemic heart disease.

The relationship between plasma renin activity (PRA) at rest and physical fitness was studied in 40 normal young subjects on a liberal sodium intake.

Jean René M'Buyamba-Kabangu

Papers

Relationship between plasma renin activity and physical fitness in normal subjects