Muscle potassium and potassium losses during hypokinesia in healthy subjects.

Hypokinesia (HK) induces electrolyte losses in electrolyte-deficient tissue, yet the mechanisms of electrolyte losses in electrolyte-deficient tissue remain unknown. Mechanisms of electrolyte deposition could be involved. To determine the effect of prolonged HK on potassium (K+) deposition were measured muscle K+ content and K+ losses. Studies were conducted on 20 physically healthy male volunteers during 30 days pre-experimental period and 364 days experimental period. Subjects were equally divided into two groups: control subjects (CS) and experimental subjects (ES). The CS group was run average distances of 9.8±1.7 km day(-1) and the ES group was walked average distances of 2.7±0.6 km day(-1). Muscle K+ content decreased (p<0.05) and plasma K+ concentration, and K+ losses in urine and feces increased (p<0.05) in the ES group compared to their pre-experimental level and the values in their respective CS group. Muscle K+ content, plasma K+ level, and urine and fecal K+ losses did not show any changes in the CS group compared to their pre-experimental values. The conclusion was that K+ losses in K+-deficient muscle of healthy subjects could have been attributable to the less efficient K+ deposition inherently to prolonged HK.

Muscle calcium metabolic effects of hypokinesia in physically healthy subjects.

The incompleteness of electrolyte deposition during hypokinesia (HK; diminished movement) is the defining factor of electrolyte metabolic changes, yet the effect of prolonged HK upon electrolyte deposition is poorly understood. The objective of this investigation was to determine the effect of muscle calcium (Ca(++)) changes upon Ca(++) losses during prolonged HK. Studies were conducted on 20 physically healthy male volunteers during a pre-experimental period of 30 days and an experimental period of 364 days. Subjects were equally divided in two groups: control subjects (CS) and experimental subjects (ES). The CS group ran average distances of 9.2 ± 1.2 km day(-l), and the ES group walked average distances of 2.3 ± 0.2 km day(-l). Muscle Ca(++) contents, plasma Ca(++) concentrations, and Ca(++) losses in urine and feces were measured in the experimental and control groups of subjects. The muscle Ca(++) contents decreased (p < 0.05), and plasma Ca(++) levels and Ca(++) losses in the urine and feces increased (p < 0.05) in the ES group compared with their pre-experimental levels and the values in their respective CS group. Muscle Ca(++) contents and plasma Ca(++) levels and urinary and fecal Ca(++) losses did not change in the CS group compared to their pre-experimental levels. It is concluded that prolonged HK increase plasma Ca(++) concentrations and Ca(++) losses in Ca(++) deficient muscle indicating decreased Ca(++) deposition.

[Biochemical diagnosis of immobilization osteoporosis].

The authors have ascertained informative laboratory tests for diagnosis of immobilization osteoporosis and prognostic tests of reparative osteogenesis in its presence. A study was conducted in 97 patients (mean age 39.8 +/- 9.5 years) with bone nonunion and immobilization osteoporosis diagnosed densitometrically (DPXA, Lunar, USA). The proposed procedures are topical if no densitometric study is available and the prediction of osteogenesis on the basis of the phosphatase index is of informative value at the X-ray negative stage (1 month after surgery). The procedures are available and cost-effective; their sensitivity is 75-77%.

Phosphate balance in phosphate supplemented and unsupplemented health subjects during and after hypokinesia.

OBJECTIVE: To demonstrate the effect of hypokinesia (HK) and post-HK on phosphate (Pi) imbalance and use of Pi with different Pi imbalance and different Pi consumption: were measured Pi balance, plasma Pi level and Pi loss during HK. METHODS: Experiments were conducted during the pre-experimental period of 30 days, and the HK period of 364-days and post-HK period of 30-days. Forty healthy male volunteers 24.2 +/- 2.0 yr, were divided into four groups: unsupplemented active control subjects (UACS), unsupplemented hypokinetic subjects (UHKS), supplemented active control subjects (SACS), and supplemented hypokinetic subjects (SHKS). All SACS and SHKS were supplemented with 0.6 mmol dicalcium-phosphate per kg body weight daily. RESULTS: During HK, Pi imbalance, serum Pi and calcium (Ca2+) levels, fecal Pi loss, and urine Ca2+ and Pi loss increased (P < 0.05) in SHKS and UHKS compared with pre-experimental values and the values in their respective active controls (SACS and UACS). The measured parameters were changed (P < 0.05) more in SHKS than in UHKS. During the initial 20-days of post-HK, serum Pi and Ca2+ levels, fecal P loss, and urine Pi and Ca2+ losses decreased (P < 0.05), while Pi imbalance remained (P < 0.05) depressed in SHKS and UHKS compared with UACS and SACS. The measured parameters were changed (P < 0.05) more in SHKS than in UHKS. CONCLUSION: The greater Pi imbalance with than without Pi supplementation shows that the risk of higher Pi imbalance is directly related to the magnitude of Pi intake. The higher Pi loss with higher than lower Pi imbalance shows that the risk of greater Pi loss is directly related to the magnitude of Pi imbalance. It is concluded that Pi imbalance increases more when the Pi consumption is higher and that Pi loss increases more with higher than lower Pi imbalance indicating that during HK Pi imbalance is due to the inability of the body to use Pi but not to the Pi shortage in the 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.

Phosphate homeotasis in healthy subjects during prolonged periodic and continuous hypokinesia.

OBJECTIVE: This study aimed to show that during hypokinesia (HK), phosphate (P(i)) imbalance increases more with higher than lower physical activity and that P(i) absorption reduces more with higher than lower P(i) imbalance in subjects with higher than lower muscular activity. METHODS: Studies were conducted on 30 healthy male subjects during 364 days of HK. They were equally divided in three groups: unrestricted active control subjects (UACS), continuously hypokinetic subjects (CHKS) and periodically hypokinetic subjects (PHKS). CHKS were kept under average walking distances of 0.5+/-0.2 km day(-1) PHKS were kept under average walking distances of 0.5+/-0.1 and running average distances of 8.7+/-1.2 km day(-l) for 5 days and 2 days per week, respectively. UACS were placed under average running distances of 8.7+/-1.2 km day(-l). RESULTS: P(i) imbalance, serum, urine and fecal P(i) levels, and urine and serum calcium (Ca(2+)) levels increased significantly (p<0.05) and P(i) absorption, and serum intact parathyroid hormone (iPTH) and 1,25-dehydroxyvitamin D (1,25 (OH)(2) D(3)) levels decreased significantly (p<0.05) in CHKS and PHKS compared with their pre-HK values and their respective active control (UACS). However, the P(i) imbalance, serum, urine and fecal P(i) levels, and serum and urine Ca(2+) levels increased more significantly (p<0.05), and P(i) absorption and serum iPTH and 1,25 (OH)(2) D(3) levels decreased more significantly in PHKS than in CHKS. CONCLUSIONS: Higher P(i) imbalance with higher than lower physical activity shows that the risk of higher P(i) imbalance is inversely related to the intensity of physical activity. Lower P(i) absorption with higher than lower P(i) imbalance shows that the risk of lower P(i) absorption is inversely related to magnitude of P(i) imbalance. In conclusion P(i) imbalance increases more with higher than lower physical activity and that P(i) absorption decreases more with higher than lower P(i) imbalance indicating that during HK the use of P(i) decreases more with higher than lower physical activity.

Tissue magnesium loss during prolonged hypokinesia in magnesium supplemented and unsupplemented rats.

This study aims at showing that during hypokinesia (HK) tissue magnesium (Mg2+) content decreases more with higher Mg2+ intake than with lower Mg2+ intake and that Mg2+ loss increases more with higher than lower tissue Mg2+ depletion due to inability of the body to use Mg2+ during HK. Studies were conducted on male Wistar rats during a pre-HK period and a HK period. Rats were equally divided into four groups: unsupplemented vivarium control rats (UVCR), unsupplemented hypokinetic rats (UHKR), supplemented vivarium control rats (SVCR) and supplemented hypokinetic rats (SHKR). SVCR and SHKR consumed 42 mEq Mg2+ per day. The gastrocnemius muscle and right femur bone Mg2+ content decreased significantly, while plasma Mg2+ level and urine and fecal Mg2+ loss increased significantly in SHKR and UHKR compared with their pre-HK values and their respective vivarium controls (SVCR and UVCR). However, muscle and bone Mg2+ content decreased more significantly and plasma Mg2+ level, and urine and fecal Mg2+ loss increased more significantly in SHKR than in UHKR. The greater tissue Mg2+ loss with higher Mg2+ intake and the lower tissue Mg2+ loss with lower Mg2+ intake shows that the risk of higher tissue Mg2+ depletion is directly related to the magnitude of Mg2+ intake. The higher Mg2+ loss with higher tissue Mg2+ depletion and the lower Mg2+ loss with lower Mg2+ tissue depletion shows that the risk of greater Mg2+ loss is directly related to the magnitude of tissue Mg2+ depletion. It was concluded that tissue Mg2+ depletion increases more when the Mg2+ intake is higher and that Mg2+ loss increases more with higher than lower tissue Mg2+ depletion indicating that during prolonged HK the tissue Mg2+ depletion is not due to the Mg2+ shortage in food but to the inability of the body to use Mg2+.

Changes in bone turnover markers during 14-day 6 degrees head-down bed rest.

Osteoporosis caused by exposure to microgravity represents a serious clinical concern, but the mechanisms have yet to be fully elucidated. The present research aimed to elucidate the effects of microgravity environments on bone turnover, with a specific focus on changes in bone resorption markers such as type I collagen cross-linked N-telopeptides (NTx) and deoxypyridinoline (Dpyr), for which scant data are available regarding detailed time course. Methods using 6 degrees head-down bed rest were utilized to simulate a microgravity environment. Eleven adult male volunteers underwent 6 degrees head-down bed rest for 14 days; measurements were made of serum and urine Ca concentrations, in addition to osteocalcin (OC), bone alkaline phosphatase (ALP), NTx, and Dpyr as bone turnover markers. By the end of bed rest, concentrations of bone ALP had significantly increased, but OC displayed a tendency toward decrease. Concentrations of Dpyr significantly increased from day 6, remaining elevated until the end of bed rest. Concentrations of NTx significantly increased on day 13 and at the end of bed rest. Serum and urinary concentrations of Ca increased significantly at the end of bed rest. Bone ALP represents a relatively early marker of osteoblast differentiation at the matrix maturation phase and OC is a late marker in osteoblast differentiation at the calcification phase. The present results therefore suggest an absolute increase in bone resorption and normal or reduced bone formation, together causing prominent uncoupling and rapid bone loss after simulated microgravity. Moreover, the present results suggest that bone resorption is enhanced at an early stage of exposure to microgravity environments.

Phosphate determination during hypokinesia and ambulation in establishing phosphate changes in trained and untrained subjects.

Hypokinesia (diminished movement) induces phosphate (P) changes; however, it is not known if P change is greater in trained than untrained subjects. Measuring P balance and P retention during hypokinesia (HK) and P load, we studied if changes in P retention and P depletion were significantly (p<0.05) greater in trained than untrained subjects. Studies were done during a 30-d pre-HK period and a 364-d HK period. Forty male trained and untrained healthy individuals aged 24.5+/-5.4 yr were chosen as subjects. All volunteers were equally divided into four groups: trained ambulatory control subjects (TACS), trained hypokinetic subjects (THKS), untrained ambulatory control subjects (UACS), and untrained hypokinetic subjects (UHKS). All THKS and UHKS were limited to an average walking distance of 0.3 km/d, and TACS and UACS were on an average running distance of 9.8 and 1.8 km/d, respectively. Subjects took daily 12.7-mmol dicalcium-phosphate/kg body weight in the form of supplementation. Negative P balance, fecal P loss, urinary P and calcium (Ca) excretion, serum P, and total Ca (Cat) levels increased significantly (p<0.05), whereas P retention, serum 1,25-dihydroxyvitamin D [1,25 (OH)2D3] and intact parathyroid hormone (iPTH) level decreased significantly (p<0.05) in THKS and UHKS when compared with their pre-HK values and their respective ambulatory controls (TACS and UACS). However, P retention, P balance, serum, urinary, and fecal P, and serum hormone level changed significantly (p<0.05) more in THKS than UHKS. Retention of P, fecal P, urinary P and Ca loss, serum P and Cat level, P balance, 1,25(OH)2D3, and iPTH level change insignificantly (p>0.05) in TACS and UACS when compared with their pre-HK control values. It was concluded that significant negative P balance may indicate P depletion, whereas significant P loss in spite of negative P balance and P load may suggest P retention incapacity; however, P depletion was greater in THKS than UHKS. Clearly, P is wasted much more in THKS than UHKS.

Fluid distribution measurement between body compartments in primates in disclosing fluid retention during prolonged hypokinesia.

Body fluid homeostasis undergoes significant changes during hypokinesia (diminished movement). Understanding of fluid transfer between body fluid compartments and its regulating mechanisms was the aim of this study for disclosing impaired fluid retention during hypokinesia (HK). Studies were done on 12 male Macaca mulatta (rhesus monkeys) aged three to five years (5.15 to 6.56 kg) during 90 days period of pre-HK and 90 days period of HK. All primates were divided equally into two groups: vivarium control primates (VCP) and hypokinetic primates (HKP). Hypokinetic primates were kept for 90 days in small individual cages that restricted their movements in all directions without hindering food and fluid intakes. Control primates were housed in individual cages without their movements being restricted. Total body fluid (TBF), intracellular fluid volume (IFV) and circulating plasma volume (CPV) decreased significantly (p < 0.05), while extracellular fluid volume (EFV) and interstitial fluid volume (IsFV) decreased significantly (p < 0.05) at the initial seven days of the HK period and after the 7th day increase progressively in HKP compared with their pre-HK values and their respective control values in VCP. Fluid excretion, urinary and plasma sodium (Na) and potassium (K) levels increased significantly (p < 0.05), while fluid intake and fluid retention decreased significantly (p < 0.05) in HKP compared with their pre-HK values and their respective controls in VCP. The measured parameters did not change in VCP compared with their pre-HK values. It was concluded that decreased IFV and CPV may demonstrate fluid depletion, while marked increase of fluid loss despite of fluid depletion may demonstrate impair fluid retention during HK. Dissociation between fluid loss and fluid depletion may demonstrate the presence of reduced fluid retention as the mechanism of development of fluid depletion during HK.

Muscle electrolyte measurements during and after hypokinesia in determining muscle electrolyte depletion during hypokinesia in the rat.

Hypokinesia (diminished movement) induces muscle mineral depletion. However, the mechanism of muscle mineral depletion during hypokinesia (HK) remains unknown. Measuring electrolyte retention and electrolyte values in muscle, plasma, and urine during and after HK, the aim of this study was to discover if HK could depress mineral retention and lead to muscle mineral depletion. Studies were done on 204 13-wk-old male Wistar rats (370-390 g) during 10 d pre-HK period, 98 d HK period, and 15 d post-HK period. Rats were equally divided into two groups: vivarium control rats (VCR) and hypokinetic rats (HKR). All hypokinetic rats were kept for 98 d in small individual cages, which restricted their movements in all directions without hindering food and water intakes. All control rats were housed for 98 d in individual cages under vivarium control conditions. Both groups of rats were pair-fed. During the HK period skeletal muscle sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), and water content and electrolyte retention decreased significantly (p < 0.05), while urinary and plasma electrolyte levels increased significantly (p < 0.05) in HKR compared with their pre-HK values and their respective VCR. During the initial days of the post-HK period, mineral retention increased significantly (p < 0.05), plasma and urinary electrolyte level decreased significantly (p < 0.05), while muscle electrolyte and water content remained significantly (p < 0.05) depressed in HKR compared with VCR. Muscle mineral and water content, electrolyte retention, plasma, and urinary electrolyte values did not change in VCR compared with their pre-HK values. It was concluded that during HK decreased muscle mineral content may suggest muscle mineral depletion, while increased urinary electrolyte loss and muscle mineral depletion may demonstrate reduced mineral retention. Reduced electrolyte excretion and depressed muscle mineral content during post-HK may indicate skeletal muscle mineral depletion during HK. Dissociation between electrolyte retention and muscle mineral depletion may demonstrate the presence of decreased electrolyte retention as the mechanism of muscle electrolyte depletion during prolonged HK.

Urinary and serum electrolyte changes in athletes during periodic and continuous hypokinetic and ambulatory conditions.

Hypokinesia (HK) (diminished movement) induces significant electrolyte changes, but little is known about the effect of periodic hypokinesia (PHK) on minerals. The aim of this study was to measure the effect of PHK and continuous hypokinesia (CHK) on urinary and serum electrolytes. Studies were done during a 30-d period of prehypokinesia (HK) and during 364 d of PHK and CHK periods. Thirty male athletes aged 24.6 +/- 7.7 yr were chosen as subjects. They were equally divided into three groups: unrestricted ambulatory control subjects (UACS), continuously hypokinetic subjects (CHKS), and periodically hypokinetic subjects (PHKS). The UACS group experienced no changes in the daily activities and regular training and they were maintained under an average running distance of 11.7 km/d. The CHKS group was limited to an average walking distance of 0.7 km/d; and the PHKS group was limited to an average walking distance of 0.7 and running distance of 11.7 km/d for 5 d and 2 d/wk, respectively, for a period of 364 d. Urinary and serum phosphate (P), calcium (Ca), sodium (Na) and potassium (K), serum intact parathyroid hormone (iPTH), calcitonin (CT), plasma renin activity (PRA) and aldosterone (PA) levels, food and water intakes, and physical characteristics were measured. Urinary P, Ca, Na, and K loss, serum Ca, P, Na, and K, and PRA and PA values increased significantly (p < or = 0.01), whereas serum iPTH and CT levels decreased significantly (p < or = 0.01) in the PHKS and CHKS groups when compared with the UACS group. However, significant (p < or = 0.01) differences were observed between PHKS and CHKS groups regarding urinary and serum electrolytes, serum and plasma hormones. Food and water intakes, body weight, body fat, and peak oxygen uptake decreased significantly (p < or = 0.01) in the CHKS group when compared with PHKS and UACS groups. Food and fluid intakes, body fat, and body weight increased significantly (p < or = 0.01), whereas peak oxygen uptake remained significantly (p < or = 0.01) higher in the PHKS group when compared with the CHKS group. Serum and urinary minerals, serum hormones, food and fluid intakes, and physical characteristics did not change significantly (p > 0.01) in the UACS group when compared with their baseline control values. It was shown that both PHK and CHK induce significant serum and urinary electrolyte changes. However, urinary and serum electrolyte changes were significantly (p < or = 0.01) greater during PHK than CHK. It was concluded that the greater the stability of muscular activity, the smaller the serum and urinary electrolyte changes during prolonged HK.

Serum, urinary, and fecal calcium changes in trained and untrained subjects during prolonged hypokinetic and ambulatory conditions.

Electrolyte metabolism undergoes significant changes in trained subjects, but it is unknown if it undergoes significant changes in untrained subjects during hypokinesia (decreased movement). The aim of this study was to measure calcium (Ca) changes in trained and untrained subjects during prolonged hypokinesia (HK). Studies were done during 30 d of a pre-HK period and 364 d of a HK period. Forty male trained and untrained volunteers aged 23-26 yr were chosen as subjects. All subjects were equally divided into four groups: trained ambulatory control subjects (TACS), trained hypokinetic subjects (THKS), untrained hypokinetic subjects (UHKS), and untrained ambulatory control subjects (UACS). The THKS and UHKS groups were kept under an average running distance of 0.7 km/d. Fecal Ca excretion, urinary Ca and magnesium (Mg) excretion, serum ionized calcium (CaI), Ca, Mg, intact parathyroid hormone (iPTH) and 1,25 dihydroxyvitamin D [1,25 (OH)2 D] concentration, body weight, and peak oxygen uptake were measured. Fecal Ca loss, urinary Ca and Mg excretion, and serum CaI, Mg, and Ca increased significantly (p < or = 0.01), whereas serum iPTH and 1,25 (OH)2 D concentration body weight and peak oxygen uptake decreased significantly (p < or = 0.01) in the THKS and UHKS groups when compared with the TACS and UACS groups. The measured parameters were much greater and much faster in the THKS group than in the UHKS group. By contrast, the corresponding parameters did not change significantly in the TACS and UACS groups when compared with the baseline control values. It was concluded that prolonged HK induces significant fecal, urinary, and serum Ca changes in the hypokinetic subjects when compared with control subjects. However, fecal, urinary, and serum Ca changes were much greater and appeared much faster in the THKS group than the UHKS group.

Plasma, urinary and fecal potassium changes in athletes during ambulatory, periodic, and continuous hypokinetic conditions.

OBJECTIVES: Prolonged hypokinesia (HK) induces significant electrolyte changes, but little is known about the effect of prolonged periodic hypokinesia on plasma, urinary, and fecal K. The aim of this study was to measure potassium (K) changes during prolonged periodic (PHK) and continuous (CHK). DESIGN AND METHODS: Studies were done during the pre HK and HK periods. Thirty male athletes were chosen as subjects. They were divided equally into three groups: unrestricted ambulatory control subjects (UACS), continuously hypokinetic subjects (CHKS), and periodically hypokinetic subjects (PHKS). The CHKS group was kept on a running distance of 0.7 km/day, while the PHKS group kept on a running distance of 0.7 and 11.7 km/day for 5 days and 2 days per week, respectively. The UACS group was on a running distance of 11.7 km/day. RESULTS: The following were measured: fecal K excretion; urinary K; sodium (Na) and chloride (CI) excretion; plasma K; Na and CI concentration; plasma renin activity (PRA) and plasma aldosterone (PA) concentration; physical characteristics; and peak oxygen uptake. Fecal K, urinary K, Na and CI excretion, plasma K, Na and CI concentration, and PRA and PA concentration, increased significantly (p< or =0.01) in the CHKS and PHKS groups when compared with the UACS group. Body weight and VO2 peak decreased significantly (p< or =0.01) in the CHKS group, while body weight increased and VO2 peak decreased significantly (p< or =0.01) in the PHKS group when compared with the UACS group. The measured parameters changed much more in the PHKS group than in the CHKS group. By contrast, the measured parameters did not change significantly in the UACS group when compared with the baseline control values. CONCLUSION: It was shown that prolonged PHK and CHK induce significant plasma and excretory K changes; however, plasma and excretory K changes were much greater in the PHKS group than in the CHKS group. It was concluded that the greater the stability of muscular activity, the smaller the plasma, urinary, and fecal K changes during prolonged HK.

Water and electrolyte excretion in rats during prolonged restriction of motor activity and chronic hyperhydration.

The objective of this investigation was to evaluate the effect of daily intakes of water and salt on water and electrolyte changes and body hydration status of rats during prolonged restriction of motor activity (hypokinesia). Ninety Wistar rats weighing 370 to 390 g were used to perform the studies: They were equally divided into three groups: 1. Unsupplemented vivarium control rats (UVCR); 2 Unsupplemented hypokinetic rats (UHKR) and 3. Supplemented hypokinetic rats (SHKR). For the simulation of the effect of hypokinesia (HK), the UHKR and SHKR groups were kept in small individual cages made of wood, which restricted their movements in all directions without hindering food and water intake. The SHKR received daily an additional amount of 5 ml water/100 g body weight and 3 g sodium chloride per 100 g body weights. During the prehypokinetic period of 15 days and during the hypokinetic period of 90 days plasma and urinary sodium and potassium, water intake and water loss, food intake, body weight, plasma osmolality, whole blood hemoglobin, hematocrit and plasma protein concentration were determined. In the UHKR group, plasma and urinary electrolytes, diuresis, plasma osmolality, whole blood hemoglobin, hematocrit and plasma protein concentration increased significantly while fluid and food intake and body weight decreased significantly when compared with the SHKR and UVCR groups. In the SHKR, plasma and urinary electrolytes, urine excretion, plasma osmolality, whole blood hemoglobin, hematocrit and plasma protein concentration decreased while food and water intake and body weight increased significantly when compared with the UHKR group. In the UVCR group, these same variables remained stable or changed very little when compared with the SHKR group throughout the experimental period. It was concluded that daily intakes of fluid and a salt supplement may be used to increase body hydration level and decrease fluid-electrolyte excretion and body weight losses during prolonged restriction of motor activity.

Magnesium loading effect on magnesium deficiency in endurance-trained subjects during prolonged restriction of muscular activity.

The aim of this study was to evaluate the effect of magnesium (Mg) loading (10.0 mg Mg/kg body wt) and daily Mg supplements (5.0 mg Mg/kg body wt) on Mg deficiency shown by increased and not by decreased serum Mg concentration during hypokinesia (decreased km number/d). The studies were done during 30 d of prehypokinesia and 364 d of hypokinesia (HK) periods. Forty endurance-trained volunteers aged 22-26 yr with a peak VO2 max of 66.3 mL.kg-1 min-1 and with an average 15.0 km/d running distance were chosen as subjects. They were equally divided into four groups: 1. Unsupplemented ambulatory control subjects (UACS). 2. Unsupplemented hypokinetic subjects (UHKS). 3. Supplemented hypokinetic subjects (SHKS). 4. Supplemented ambulatory control subjects (SACS). The SHKS and SACS groups took daily 5.0 mg elemental Mg/kg body wt and subjected to Mg loading (10.0 mg Mg/kg body wt). Both the SHKS and UHKS groups were maintained under an average running distance of 4.7 km/d, whereas the SACS and UACS groups did not experience any modifications to their normal training routines and diets. During the prehypokinetic and hypokinetic periods, excretion of Mg in feces and urine, concentration of Mg in serum, and Mg balance were measured. Urinary and serum sodium (Na), potassium (K), and calcium (Ca) were also determined. In both SHKS and UHKS groups, fecal Mg loss, urinary excretion of electrolytes, and serum concentrations of electrolytes increased significantly (p < or = 0.05) when compared with the SACS and UACS groups. During Mg loading tests, urinary and fecal Mg excretion was also greater in the SHKS and UHKS groups than in the SACS and UACS groups. Throughout the study, Mg balance was negative in the SHKS and UHKS groups, whereas in the SACS and UACS groups, Mg balance was positive. It was concluded that significant losses of Mg occurred in the presence of negative Mg balance and Mg deficiency in endurance-trained subjects during prolonged exposure to HK, daily mg supplements, and Mg loading tests. This suggests that Mg is not entering or being retaining by the bones and cells of many tissues where most Mg is deposited normally, resulting in Mg deficiency as was shown by the increased serum Mg concentration.

Fluid electrolyte changes during prolonged restriction of motor activity in rat.

Water and electrolyte changes in urine and plasma of rats during prolonged restriction of motor activity (hypokinesia), have been studied, on 90 male Wistar rats (375 to 396 g) during a 15 day period of prehypokinesia and during a 90 day period of hypokinesia (HK). All rats were divided equally into two groups: rats placed under ordinary vivarium conditions served as vivarium control rats (VCR) and rats subjected to HK served as hypokinetic rats (HKR). The hypokinetic effect was carried out by keeping the HKR group in small individual cages that restricted all their movements in all directions without hindering food and water intake. During the 15 days of the prehypokinetic period and during the 90 days of the hypokinetic period, fluid consumed and eliminated in urine, food intake, body weight, plasma sodium and potassium concentration and excretion thereof in urine, plasma osmolality, total protein plasma concentration, whole blood haemoglobin and haematocrit concentration were measured. In the HKR group water and food intakes decreased significantly (p < 0.05) when compared with the VCR group, whilst diuresis, excretion of sodium and potassium in urine, plasma sodium and potassium concentration, plasma osmolality, plasma protein concentration, whole blood haemoglobin and haematocrit increased significantly (p < or = 0.05) when compared with the VCR group. It was concluded that prolonged exposure to HK induces significant changes in water balance and in both urinary and plasma sodium and potassium in rat.

Daily zinc supplementation effect on zinc deficiency in rats during prolonged restriction of motor activity.

The objective of this investigation was to evaluate the effect of 47 mg zinc supplementation on deficiency of zinc in rats during 98 d of restriction of motor activity (hypokinesia), which appeared by higher plasma zinc concentration. One Hundred 13-week-old Sprague-Dawley male rats weighing 360-390 g were used to perform the studies: They were equally divided into four groups: 1. Unsupplemented control animals (UCA); 2. Unsupplemented hypokinetic animals (UHA); 3. Supplemented control animals (SCA); and 4. Supplemented hypokinetic animals (SHA). For the simulation of the effect of hypokinesia (HK), the UHA and SHA were kept in small individual cages made of wood, which restricted their movements in all directions without hindering food and water intake. The SCA and SHA received daily with their food an additional amount of zinc. Before and during the experimental period of 98 d, plasma, urinary and fecal zinc, balance of zinc, food intake, and body weight were determined at different intervals. In the SHA and UHA, the concentration of zinc in plasma, and the elimination of zinc in urine and feces increased significantly when compared with the SCA and UCA, whereas the balance of zinc was negative. The body weight and food intake decreased significantly in the SHA and UHA when compared with the SCA and UCA. The increased plasma concentration of zinc in both the SHA and UHA groups was in contrast to the observed hypozincnemia during prolonged immobilization as during prolonged hospitalization. This reaction suggests that there may be some other mechanisms that are affecting the process of control and regulation of zinc metabolism during prolonged HK. It was concluded that exposure to prolonged restriction of motor activity of rats induces significant increases in plasma concentration, fecal and urinary elimination of zinc in the presence of negative zinc balance and regardless the daily intake of large amounts of zinc with their food, leading to zinc deficiency.

Daily magnesium supplementation on serum and urinary magnesium changes in rats during prolonged restriction of motor activity.

The objective of this investigation was to determine whether a plentiful magnesium (Mg2+) supplementation might be used to normalize or prevent Mg deficiency. This is manifested by increased rather than decreased serum Mg2+ concentration as is observed during prolonged hospitalization, which is developed during prolonged hypokinesia (HK) (decreased motor activity). Eighty male Wistar rats with an initial body weight of 370-390 g were used to perform the studies: They were equally divided into four groups: 1. Unsupplemented control animals (UCA); 2. Supplemented control animals (SCA); 3. Unsupplemented hypokinetic animals (UHA); and 4. Supplemented hypokinetic animals (SHA). For the simulation of the hypokinetic effect, the hypokinetic animals were kept in small individual cages made of wood which restricted their movements in all directions without hindering food and water intake. The control and hypokinetic supplemental animals receive 0.9 mg/mL Mg sulfate daily with their drinking water. Prior to and during the experimental period, urinary excretions of Mg, calcium, and phosphate along with their concentrations in serum, water intake, and urine excretion, and body weight were determined in the control and hypokinetic animals. In the supplemental and unsupplemental hypokinetic rats, urinary excretions and serum concentrations of electrolytes increased significantly, whereas serum concentration and urinary excretion thereof remained unchanged in the supplemented and unsupplemented control animals. It was concluded that a daily intake of large amounts of Mg supplementation cannot be used to prevent or normalize Mg deficiency in rats during prolonged exposure to HK.

Urea disturbances in serum and urine of endurance trained volunteers during prolonged restriction of muscular activity.

The objective of this study was to determine the disturbances of urea in serum and urine of endurance trained volunteers during prolonged exposure to hypokinesia (decreased number of km/day). The studies during hypokinesia (HK) were performed for 364 days on twenty long-distance runners in the age of 23 to 26 years, with an average peak oxygen uptake, of 66 ml.kg.min-1. All volunteers were divided into two equal groups: Ten volunteers were placed on a continuous regime of exercise 14.8 km/day and served as control subjects (CS). The remaining volunteers were subjected to continuous HK without the use of any preventive measures and were considered as the hypokinetic subjects (HS). For the simulation of the hypokinetic effect, the HS were kept continuously under an average of 2.7 km/day for the duration of the study. Prior to exposure to HK, the HS were on the same exercise regime as the CS. During a 60 day pre-HK period and during the experimental period, urinary excretion of urea, creatinine, sodium, potassium and calcium and concentrations thereof in serum were measured. In the HS the concentrations of urea, creatinine, sodium, potassium and calcium in serum and the rate of excretion thereof in urine increased significantly when compared to the CS. It was concluded that prolonged restriction of muscular activity induces significant disturbances of urea in serum and urine of endurance trained volunteers.