Mechanism of sodium loss with muscle sodium deficiency in sodium supplemented and unsupplemented subjects during hypokinesia.

BACKGROUND: This study aims at showing the effect of hypokinesia (HK) on sodium (Na+) loss with different muscle Na+ deficiency and different Na+ intake. Muscle Na+ content, plasma Na+ level and Na+ loss with and without Na+ supplementation were measured. METHODS: This study was conducted on 40 healthy male volunteers during a pre-experimental and an experimental period. Subjects were equally divided into four groups: unsupplemented active control subjects (UACS), unsupplemented hypokinetic subjects (UHKS), supplemented active control subjects (SACS) and supplemented hypokinetic subjects (SHKS). A daily supplementation of 3.21 mmol of sodium chloride (NaCl) per kg body weight was given to subjects in the SACS and SHKS groups. RESULTS: Muscle Na+ content levels decreased and plasma Na+ levels, and levels of Na+ loss in urine and feces increased (p<0.05) in the SHKS and UHKS groups compared to their pre-experimental values and the values in the respective active control groups (SACS and UACS). However, muscle Na+ content levels decreased more (p<0.05), and plasma Na+ levels and levels of Na+ loss in urine and feces increased more (p<0.05) in the SHKS group than in the UHKS group. CONCLUSIONS: The greater muscle Na+ deficiency with higher than lower Na+ consumption shows that the risk of greater muscle Na+ deficiency is directly related to Na+ consumption. The higher Na+ loss with higher than lower muscle Na+ deficiency shows that the risk of greater muscle Na+ loss is directly related to muscle Na+ deficiency. It is concluded that muscle Na+ deficiency is more evident when Na+ consumption is higher and that muscle Na+ loss was more exacerbated with higher than lower muscle Na+ deficiency indicating that during prolonged HK the muscle Na+ deficiency is due to the inability of the body to use Na+, but not to Na+ shortage in diet.

Electrolyte homeostasis in trained and untrained healthy subjects during prolonged hypokinesia.

OBJECTIVE: This study aimed to show that during hypokinesia (HK) electrolyte imbalance increases more in trained than untrained subjects and that electrolyte loss increases more with higher than lower electrolyte imbalance in trained than untrained subjects. METHODS: Studies were conducted during 364-day HK. Subjects were equally divided in four groups: trained ambulatory control subjects (TACS), trained hypokinetic subjects (THKS), untrained ambulatory control subjects (UACS) and untrained hypokinetic subjects (UHKS). THKS and UHKS were limited to average walking distances of 0.5+/-0.1 km day(-1). TACS were running average distances of 9.8+/-1.3 and UACS were walking average distances of 1.8+/-0.2 km day(-1). RESULTS: Plasma potassium (K(+)), calcium (Ca(+2)) and magnesium (Mg(+2)) levels, urine and fecal electrolyte excretion, electrolyte imbalance, plasma aldosterone (PA) and plasma rennin activity (PRA) increased significantly (p<0.05), while electrolyte absorption, plasma intact parathyroid hormone (iPTH) and dihydroxyvitamin D (1,25 (OH)(2) D(3)) levels decreased significantly (p<0.05) in THKS and UHKS compared with their pre-HK values and their respective controls (TACS and UACS). Electrolyte imbalance, plasma electrolyte levels, urine and fecal electrolyte excretion, PA and PRA levels increased more significantly (p<0.05), while electrolyte absorption, plasma iPTH and 1, 25 (OH)(2) D(3) levels decreased more significantly (p<0.05) in THKS than in UHKS. CONCLUSION: The higher electrolyte imbalance in trained as compared to untrained subjects shows that the risk of higher electrolyte imbalance is inversely related to the magnitude of physical conditioning. The higher electrolyte loss with higher than lower electrolyte imbalance shows that the risk of higher electrolyte loss is inversely related to the magnitude of electrolyte imbalance. In conclusion electrolyte imbalance increases more in trained than untrained subjects and that electrolyte loss increase more with higher than lower electrolyte imbalance indicating that during prolonged HK the use of electrolytes decreases more with higher than lower physical conditioning.