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.

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

The objective of this investigation was to evaluate the effect of magnesium (Mg) supplements in rats during prolonged restriction of motor activity (hypokinesia [HK]) and in the presence of Mg deficiency, which is characterized by increased rather than decreased plasma Mg concentration, as occurs in ambulatory conditions. The studies were performed during 98 days of HK on 100 13-week-old Sprague-Dawlay male rats weighing 360 to 390 g. 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 hypokinetic effect, SHA and UHA were kept for 98 days in small individual wood cages that restricted their movements in all directions without hindering food and water intake. The SCA and SHA took daily with their food an additional 0.35 mg of Mg. Before and during the hypokinetic period of 98 days, Mg in plasma, urine, and feces, balance of Mg, food intake of Mg, and body weight were determined at different intervals. In SHA and UHA, plasma Mg concentration and excretion of Mg in urine and feces increased significantly compared with SCA and UCA. Magnesium balance was negative in UHA and AHA throughout the hypokinetic period. Body weight and a food intake decreased significantly in SHA and UHA when compared with SCA and UCA. Significant losses of Mg in SHA and UHA occurred in the presence of Mg deficiency and suggest that prolonged HK induces another factor that influences Mg metabolism. We conclude that prolonged HK causes significant changes in Mg values of plasma, urine, and feces and a negative Mg balance in rats, despite Mg supplements leading to Mg deficiency.

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.

Electrolyte concentration in skeletal muscles and plasma of rats during and after exposure to hypokinesia and hyperhydration

The objective of this investigation was to determine electrolyte concentration in skeletal muscles and plasma of rats during 90 days of hypokinesia (decreased motor activity) and 15 days of posthypokinesia. The animals were divided into three groups: 1) supplemented hypokinetic rats (SHR), i.e., rats subjected to hypokinesia and taking daily an additional 9 ml water per 100 g body weight plus 6 ml isotonic sodium chloride per 100 g body weight; 2) unsupplemented hypokinetic rats (UHR), i.e., rats subjected to hypokinesia; 3) vivarium control rats (VCR), i.e., rats placed under ordinary vivarium conditions. Hypokinesia was effected by keeping SHR and UHR animals in small individual cages that restricted their movements in all directions without hindering food and water intake. Determinations were made of water and electrolyte (sodium potassium, calcium, magnesium) concentrations in muscle tissue; concentration of electrolytes (sodium, potassium, calcium, magnesium, phosphorus, chloride) in plasma; body weight; fluid consumed and eliminated in urine; whole blood, red blood cell and plasma volumes; hematocrit content and plasma protein concentration. During the hypokinetic period, electrolytes and water concentration in muscle tissue and plasma electrolyte concentration changes significantly in the UHR when compared with SHR and VCR while in comparing the SHR with the VCR these same variables had no significant changes. Body weight, water balance, volume of blood, red blood cell and plasma, hematocrit and plasma protein concentration in the UHR were also significantly different when compared with the VCR. No significant difference was seen in these parameters when the SHR and VCR were compared. During the initial seven days of the posthypokinetic period the changes in these same parameters remained significantly different in the UHR when compared with the SHR and VCR while changes were insignificant when the SHR and the VCR were compared. It was concluded that daily hyperhydration may be used to attenuate or normalize water and electrolyte concentrations in muscles and plasma of rats subjected to prolonged restriction of motor activity.

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 hyperhydration effect on electrolyte deficiency of endurance-trained subjects during prolonged hypokinesia

The aim of this study was to evaluate the effect of a daily intake of fluid and salt supplementation (FSS) on the deficiency of electrolytes, which is characterized by higher rather than lower plasma concentration of electrolytes during prolonged hypokinesia (HK) (decreased number of km taken per day). Forty long distance runners aged 22-25 yr with a peak VO2 65.4 mL min(-1) kg(-1) with an average 14.2 km d running distance were selected as subjects. They were equally divided into four groups: 1) unsupplemented control subjects (UCS); 2) unsupplemented hypokinetic subjects (UHS); 3) supplemented hypokinetic subjects (SHS), and 4) supplemented control subjects (SCS). During the investigation of 364 d, groups 2 and 3 maintained an average running distance of less than 4.7 km per day, groups 1 and 4 did not experience any modification in their normal training routines and diets. During the preexperimental period of 60 d and during the experimental period of 364 d urinary excretion of electrolytes and concentrations of sodium, potassium, calcium, and magnesium in plasma were determined. Whole blood hemoglobin, hematocrit index, plasma osmolality, and plasma protein concentration were measured. In the UHS plasma concentration of electrolytes and urinary excretion thereof, fluid elimination, hematocrit, whole blood hemoglobin, plasma osmolality, and plasma protein concentration increased significantly (p < 0.05) when compared with the UCS, SCS, and SHS groups. In the SHS plasma concentration of electrolytes and urinary excretion thereof, fluid excretion, whole blood hemoglobin, hematocrit, plasma osmolality, and plasma protein concentration decreased when compared with the UHS and increased insignificantly when compared with the UCS and SCS groups. It was concluded that FSS may be used to prevent or minimize electrolyte deficiency in endurance-trained volunteers during prolonged restriction of muscular activity.

Bone histomorphometric changes in trained subjects during prolonged restriction of muscular activity and chronic hyperhydration

BACKGROUND

The purpose of this study was to determine whether histomorphometric changes, which are developed during prolonged hypokinesia (decreased number of km/day) could be prevented or minimized with a daily intake of fluid and salt supplementation (FSS).

METHODS

The studies on hypokinesia (HK) were performed for 364 days on thirty endurance trained male volunteers (ETV) in the age of 19 to 25 years, with an average peak oxygen uptake (POU), of 65 mL/kg-1.min-1. All volunteers were divided into three equal groups: ten volunteers were placed on a continuous regime of exercise of 13.8 km/day and served as control subjects. Ten volunteers were subjected to continuous HK without FSS and were considered as the unsupplemented hypokinetic subjects (UHS). The remaining volunteers were under continuous HK and FSS and were considered as the supplemented hypokinetic subjects (SHS). For the simulation of the hypokinetic effect, the SHS and UHS groups were kept continuously under an average of 2.7 km/day for the duration of the experiment. Prior to exposure to HK, all volunteers were on the same exercise regime as the control subjects. During the 60 day pre-HK period and during the experimental period, the following parameter were determined: sodium and calcium in urine and plasma, hemoglobin (Hb), hematocrit (Hct), plasma osmolality, plasma protein concentration, plasma renin activity, aldosterone and parathyroid hormone (PTH) concentration.

RESULTS

In the UHS iliac crest cancellous bone volume and PTH content decreased, urinary and plasma electrolytes, plasma renin activity, aldosterone, plasma osmolality, protein content, Hb and Hct increased significantly. In the SHS iliac crest cancellous bone volume and PTH content increased, while electrolytes in urine and plasma Hb, Hct, osmolality, protein, aldosterone and plasma renin activity decreased.

CONCLUSIONS

It was concluded that daily intake of FSS may be used to minimize or prevent histomorphometric changes in endurance trained volunteers during exposure to prolonged HK.

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.

Water metabolic parameter changes in rhesus monkeys during exposure to prolonged restriction of motor activity

The objective of this investigation was to determine the effect of prolonged restriction of motor activity (hypokinesia [HK]) on several parameters of water metabolism in primates. The studies were performed on 12 rhesus monkeys aged 4-5 yr (5.10-6.85 kg) during the hypokinetic period of 90 d and during the prehypokinetic period of 30 d. They were divided into two equal groups: the first group was placed under ordinary vivarium conditions (vivarium control animals) and the second group was subjected to 90 d of HK (hypokinetic animals). For the simulation of the hypokinetic effect, the primates were immobilized on their abdomens in special tables. The legs of the monkeys were immobilized with hip and knee joints extended. The primates retained freedom of movement at elbow, wrist, and ankle. During the pre-experimental period of 30 d and during the experimental period of 90 d, the following variables were determined: body weight, total body fluid content, specific total body fluid, mean fluid consumed and eliminated in urine, specific plasma resistance, hematocrit level, and plasma concentrations of sodium (Na) and potassium (K). In the hypokinetic primates, body weight decreased significantly when compared to the controls. Mean fluid intake, total body fluid, and specific total body fluid decreased, whereas mean daily fluid loss and specific mean daily fluid elimination increased significantly. Specific plasma resistance, hematocrit level, and plasma electrolyte concentrations increased significantly when compared to the control primates. It was concluded that prolonged restriction of motor activity induces significant changes in water metabolic parameters of primates leading in decreased total water content of the body.

Serum urate and cholesterol levels in endurance trained volunteers during acute and rigorous bed rest conditions

The objective of this investigation was to determine serum urate and cholesterol concentrations in endurance trained volunteers during exposure to acute (abrupt restriction of muscular activity) and rigorous bed rest conditions of seven days. The studies were performed on 30 long distance runners aged 22-25 who had a peak of VO2 of 65.5 +/- 2.7 ml.kg-1.min-1 on the average prior to their participation in the study. The volunteers were divided into three equal groups: the volunteers in the 1st group were under normal ambulatory conditions (control subjects), the volunteers of the 2nd group subjected to an acute bed rest regime (acute bed rested subjects) and the volunteers of the 3rd group were submitted to a rigorous bed rest regime (rigorous bed rested subjects). All volunteers were on an average of 14.2 km/day before taking part in the study. The 2nd and 3rd groups of volunteers were kept under a rigorous bed rest regime for seven days. During the perbed rest period and during the actual bed rest periods (acute and rigorous bed rest periods) serum cholesterol and uric acid levels were measured. During the 1st day of acute and rigorous bed rest periods serum uric acid and cholesterol concentrations increased significantly (p < or = 0.05), on the 3rd day increased somewhat more and during the 7th day they increased further. These changes were more pronounced during acute than rigorous bed rest conditions. It was concluded that increases in uric acid and cholesterol concentrations in serum appear to reflect more stresses that associated with acute than rigorous bed rest conditions in endurance trained volunteers.

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.

Fluid electrolyte changes in trained subjects after water loading and during restriction of muscular activity and chronic hyperhydration

The objective of this investigation was to determine fluid electrolyte changes after water-loading tests and during hypokinesia (decreased number of km taken per day) and daily intake of fluid and salt supplementation (FSS). The studies during hypokinesia (HK) were performed for 364 d on 30 endurance-trained male volunteers in the age range of 23-26 yr, with an average peak oxygen uptake, POU, of 64 mL/kg/min. All volunteers were divided into three equal groups: 10 volunteers were placed on a continuous regime of exercise of 14.4 km/d and served as control subjects (CS); 10 volunteers were submitted to continuous HK without FSS and were considered as the unsupplemented hypokinetic subjects (UHS); and 10 volunteers were under continuous HK and FSS and were considered as the supplemented hypokinetic subjects (SHS). For the simulation of the hypokinetic effect, the UHS and SHS groups were kept continuously under an average of 2.7 km/d for the duration of the study. Prior to exposure to HK, the two groups of volunteers were on the same exercise regime as the control group. During a 60-d preexperimental period and during the remainder of the study, water-loading tests with a water load of 20 mL/kg body wt/min were performed, and urinary and plasma electrolytes (sodium, potassium, calcium, and magnesium) were measured. In the SHS group, urinary excretion of electrolytes and plasma electrolyte content decreased, while in the UHS these values increased after water loading tests and during HK. Based on the obtained data, it is concluded that chronic hyperhydration may be used to prevent or minimize urinary and plasma electrolyte changes in endurance-trained volunteers after water-loading tests and during prolonged restriction of muscular activity.

Urinary and plasma calcium changes in endurance trained volunteers during exposure to acute and rigorous bed rest conditions

The purpose of the present study was to evaluate the effect of acute (abrupt restriction of muscular activity) and rigorous bed-rest conditions on urinary and plasma calcium changes in endurance trained volunteers. The studies were performed on 30 long distance runners ages 23-25 who had a peak oxygen uptake of 66.0 mL/min/kg and had run 14.0 km/d on the average prior to their participation in the study. The volunteers were divided into three groups: The volunteers in the first group were under normal ambulatory conditions (control subjects), the second group was subjected to an acute bed-rest regime (acute bed-rested subjects), and the third group was submitted to a rigorous bed-rest regime (rigorous bed-rested subjects). The second and third groups of volunteers were kept under a rigorous bed rest regime for 7 d. During the pre-bed-rest period and during the actual bed-rest periods (acute and rigorous bed-rest periods), urinary excretion of calcium and plasma calcium and parathyroid hormone (PTH) concentrations were determined. During the 1st d of acute and rigorous bed-rest periods, urinary excretion and plasma concentration of calcium increased significantly (P < or = 0.05), while plasma parathyroid hormone content decreased significantly (P < or = 0.05). On the 3rd d of the experimental period, urinary excretion and plasma calcium concentration decreased somewhat, during the 7th d, calcium in urine and plasma increased further, while parathyroid hormone content in plasma increased somewhat on the 3rd d and decreased again on the 7th d of the experimental period. The changes were more pronounced in the volunteers who were subjected to acute bed-rest conditions than in the volunteers who were submitted to rigorous bed-rest conditions. It was concluded that exposure to acute bed-rest conditions induces significantly greater urinary and serum calcium changes than rigorous bed-rest conditions in endurance trained volunteers.

Renal function in endurance trained volunteers during prolonged restriction of muscular activity

It has been demonstrated that changes in the functional status of the kidneys are basically responsible for the impaired fluid-electrolyte metabolism in physically healthy volunteers during hypokinesia (decreased number of walking steps/day). Thus, the objective of this investigation was to determine the functional changes of the kidneys of 20 endurance trained male volunteers aged 23 to 26 years with an average maximum oxygen uptake 65 ml.kg-1.min-1 during 364 days of hypokinesia (HK). All volunteers were on 14.6 km/day (10,000 running steps/day) prior to their exposure to HK. All volunteers were randomly assigned to one of the two groups: Ten volunteers were placed continuously under 14.6 km/day (10,000 running steps/day) (control subjects) and ten to 2.9 km/day (3,000 walking steps/day) (hypokinetic subjects). During the prehypokinetic period of 60 days and during the hypokinetic period of 364 days urinary and plasma electrolytes, glomerular filtration rate (GFR), renal plasma flow (RPF), were determined and isotope renographic tests were performed. The hypokinetic volunteers displayed a significant increase in urinary and plasma concentrations of electrolytes, a significant decrease in glomerular filtration rate and renal plasma flow, incorporation of isotope in the kidneys increased significantly while elimination of 131I-Hippuran from blood and kidneys decreased significantly. It is concluded that prolonged restriction of muscular activity induces significant changes in the examined renographic parameters of endurance trained volunteers which may be related to abnormalities of renal pelvis function or calyceal function.

Potassium changes in trained subjects after potassium loading and during restriction of muscular activity and chronic hyperhydration

The objective of this investigation was to determine whether urinary and plasma potassium changes developed during prolonged hypokinesia (HK) (decreased number of km/d) in endurance-trained subjects could be minimized or reversed with a daily intake of fluid and salt supplementation (FSS). The studies were performed on 30 endurance-trained male volunteers aged 23-26 yr with an average peak oxygen uptake of 65 mL/kg min during 364 d of HK. All volunteers were on an average of 13.8 km/d prior to their exposure to HK. All volunteers were randomly divided into three groups: 10 volunteers were placed continuously under an average of 14.0 km/d (control subjects), 10 volunteers were subjected continuously to an average of 2.7 km/d (unsupplemented hypokinetic subjects), and 10 volunteers were submitted continuously to an average of 2.7 km/d, and consumed daily an additional amount of 0.1 g sodium chloride (NaCl)/kg body wt and 30 mL water/kg body wt (supplemented hypokinetic subjects). During the prehypokinetic period of 60 d and during the hypokinetic period of 364 d, potassium loading tests were performed with 1.5-1.7 mEq potassium chloride/kg body wt, and potassium, sodium, and chloride excretion in urine and potassium, sodium, and chloride in plasma were determined. In the unsupplemented hypokinetic volunteers, urinary excretion of electrolytes and concentrations of electrolytes in plasma increased significantly as compared to the control and supplemented hypokinetic groups of volunteers. It was concluded that daily intake of fluid and salt supplementation had a favorable effect on regulation of urinary and plasma potassium changes in trained subjects during prolonged HK.

Electrolyte metabolic changes in rats during and after exposure to hypokinesia

The objective of this study was to determine fluid-electrolyte changes in male Wistar rats during 90 days of hypokinesia (decreased motor activity) and 15 days posthypokinesia. The animals were divided into two groups: rats subjected to hypokinesia served as experimental animals and rats placed under vivarium conditions served as control animals. The hypokinetic effect was carried out by keeping the experimental rats in small individual cages which restricted all their movements without hindering food and water intake. Determination was made of body weight, fluid consumed and eliminated in urine, sodium and potassium excretion in urine, concentrations of sodium and potassium in urine, the hematocrit level and water content in blood, and plasma concentration of sodium and potassium. During the experimental period body weight, water intake, urinary sodium and potassium content, and water content in blood decreased significantly, while electrolyte excretion in urine, plasma electrolyte concentration, hematocrit content and fluid excretion in urine increased significantly in the hypokinetic animals when compared with the control animals. During the initial seven days of the postexperimental period, water intake increased significantly while hematocrit level, water content in blood, and electrolyte plasma concentration remained markedly higher, and the fluid electrolyte excretion and electrolyte concentration thereof in urine decreased significantly. However, all these changes reverted back to the control level by the end of the post-experimental period. It was concluded that prolonged hypokinesia (HK) and the initial stages of post hypokinesia are associated with significant sodium and potassium changes and water consumption and elimination disturbances.

Water electrolyte concentrations in different segments of the kidney of rats during prolonged restriction of motor activity

The objective of this investigation was to determine the electrolyte concentration in plasma and in different segments of the kidney and kidney structural changes during a 90-day restriction of motor activity (hypokinesis). The studies were performed on 120 male Wistar rats divided into two groups. The first group was placed under ordinary vivarium conditions (vivarium control animals) and the second group subjected to hypokinesia (hypokinetic animals). The hypokinetic effect was carried out by keeping the rats in small individual wooden cages which restricted their movements without hindering food and water intake. Determinations were made of the concentration of sodium and potassium in plasma and in the renal cortex, external medullary layer and papilla. The concentration of electrolytes increased in the plasma while in the different segments of the kidney--primarily in the wet cortical and medullary matter--it decreased significantly compared with the control animals. Microdissection of the kidney of rats also demonstrated significant structural differences in nephrons of the hypokinetic animals when compared with the controls. Prolonged restriction of motor activity induces significant changes in the structure of the nephrons and in the electrolyte concentration of the plasma and different segments of the kidney.

Changes in plasma volume during prolonged restriction of motor activity: effect of chronic hyperhydration

Prolonged reduction of number of steps taken per day by healthy subjects (hypokinesia), is associated with a decrease in plasma volume (PV), which may contribute to the development of several so-called hypokinetic disorders seen immediately during exposure to hypokinesia (HK). The purpose of this study was to determine whether a daily intake of fluid and salt supplementation (FSS), would attenuate this loss of PV. Thirty male long distance runners (20-25 years of age) completed this investigation. Ten volunteers placed under a normal ambulatory life (control subjects), ten volunteers were subjected to continuous restriction of motor activity without using FSS (hypokinetic subjects) and ten volunteers were submitted to continuous restriction of motor activity and took daily FSS (hyperhydrated subjects). For the simulation of the hypokinetic effect the hypokinetic and hyperhydrated volunteers were kept under 2.7 km/day (3,000 steps/day). Plasma volume decreased significantly (p < 0.05) in the hypokinetic volunteers during HK, from 3.010 +/- 81 to 2.693 +/- 52 ml. The volunteers who were submitted to combined HK and FSS, had a significant (p < 0.05) increase in PV during HK, from 2.940 +/- 72 to 3.327 +/- 72 ml. There were demonstrable significant differences in PV between the hyperhydrated and hypokinetic groups of volunteers. Thus, prolonged restriction of motor activity appears to have significant effects on the loss of PV, whereas chronic hyperhydration significantly increases PV.

Effect of daily hyperhydration on fluid-electrolyte changes in endurance-trained volunteers during prolonged restriction of muscular activity

The aim of this investigation was to evaluate the effect of a daily intake of fluid and salt supplementation on fluid and electrolyte losses in endurance-trained volunteers during prolonged restriction of muscular activity (hypokinesia). The studies were performed on 30 long-distance runners aged 23-26 who had a peak oxygen uptake of 65.5 mL/kg/min and had taken 13.8 km/d on average prior to their participation in the study. The volunteers were divided into three groups: The volunteers in the first group were placed under normal ambulatory conditions (control subjects), the second group of volunteers subjected to hypokinesia alone (hypokinetic subjects), and the third group of volunteers was submitted to HK and consumed daily 0.1 g sodium chloride (NaCl)/kg body wt and 26 mL water/kg body wt (hyperhydrated subjects). The second and third group of volunteers were kept under an average of 2.7 km/d for 364 d. During the pre-experimental period of 60 d and during the experimental period of 364 d sodium, potassium, calcium, and magnesium in urine and plasma were determined. Blood was also assayed for osmolality, hemoglobin, hematocrit, plasma volume, plasma renin activity and plasma aldosterone. Mean arterial blood pressure was also determined. In the hyperhydrated volunteers plasma volume and arterial blood pressure increased, whereas plasma osmolality, plasma renin activity, plasma aldosterone, hematocrit, hemoglobin concentration, and urinary excretion and concentrations of electrolytes in plasma decreased. In the hypokinetic volunteers, plasma volume and arterial blood pressure decreased significantly, whereas hematocrit values, hemoglobin concentration, plasma osmolality, plasma renin activity, plasma aldosterone, and electrolytes in urine and plasma increased significantly during the experimental period. It was concluded that chronic hyperhydration may be used in minimizing fluid and electrolyte losses in endurance-trained volunteers during prolonged restriction of muscular activity.

Fluid-electrolyte changes in physically conditioned subjects after hypokinesia and chronic hyperhydration

The aim of this study was to determine whether fluid-electrolyte changes, which are developed during prolonged hypokinesia (decreased number of km per day), can be prevented or minimized with the use of a daily intake of fluid and salt supplementation (FSS). The experiments on hypokinesia (HK) were performed for 364 days on 18 endurance-trained male volunteers in the age range of 21-23 years, with an average maximum oxygen uptake of 67 ml kg-1. All volunteers were divided into three equal groups: six volunteers were placed on a continuous regime of exercise of 14.0 km day-1 and served as control subjects. Six volunteers were subjected to continuous HK without FSS and were considered as the unsupplemented hypokinetic subjects (UHS). The remaining volunteers were under continuous HK and FSS and were considered as the supplemented hypokinetic subjects (SHS). For the simulation of the hypokinetic effect, the UHS and SHS groups were kept continuously under an average of 2.7 km day-1 for the duration of the experiment. Prior to exposure to HK, all volunteers were on the same exercise regime as the controls. During the pre-experimental period of 60 days and during the post-experimental period, urinary excretion of electrolytes and concentrations of sodium, potassium, calcium and magnesium in serum as well as serum osmolality were determined. An increased renal excretion of fluid and electrolytes and a decreased serum electrolyte concentration were observed in the SHS, while a decreased renal excretion of fluid and electrolytes and an increased serum electrolyte concentration were observed in the UHS, during the initial stages of the post-hypokinetic period. By day 30 of the post-hypokinetic period these changes were reverted back to the control levels. We concluded that chronic hyperhydration may be used to attenuate urinary and serum electrolyte changes in endurance-trained volunteers after exposure to prolonged HK.

Renal excretion of end products of protein metabolism in urine of endurance trained subjects during restriction of muscular activity

The objective of this investigation was to determine the rate of renal excretion of end products of protein metabolism in urine of 20 endurance trained male volunteers aged 23-26 years with an average maximum oxygen uptake of 66 ml.kg-1.min-1 during 364 days of hypokinesia (decreased number of running steps/day). All volunteers were on an average of 10,000 running steps/day prior to their exposure to hypokinesia (HK). All volunteers were randomly assigned to one of the two groups. Ten volunteers were placed continuously under 13.9 km/day (10,000 running steps/day) (control subjects) and ten volunteers were subjected continuously under 2.7 km/day (3,000 walking steps/day) (hypokinetic subjects). During the prehypokinetic period of 60 days and during the hypokinetic period of 364 days urinary excretion of total nitrogen, urea and creatinine were determined. All hypokinetic volunteers displaced significant increases in renal excretion of total nitrogen, urea and creatinine as compared to the control group of volunteers. It is concluded that prolonged restriction of muscle activity induces significant increases in urinary excretion of end products of nitrogen metabolism in endurance trained volunteers.

Electrolyte and water contents in organs and tissues of rats during and after exposure to prolonged restriction of motor activity

Sodium and potassium concentrations in organs and tissues of rats have been determined during hypokinesia (HK) and posthypokinesia (post-HK) periods. The study was performed on 180 male Wistar rats with an initial body weight of 370 to 390 g. They were divided into control and experimental groups: the 1st group of rats was placed under ordinary vivarium conditions (control) and the 2nd group was subjected to 90 days of HK (hypokinetic animals). The animals were kept in small individual wooden cages which restricted their movements in all directions without hindering feed and water intake. On the 30th, 60th and 90th day of the HK period and on the 5th, 10th and 15th day of the post-HK period animals were decapitated, and potassium and sodium concentrations were measured in the myocardium, skeletal muscles, erythrocytes and plasma. Fluid content was also determined in the myocardium and skeletal muscles. During both the HK period and initial stages of the post-HK period the concentration of sodium and potassium in the myocardium, skeletal muscle, plasma and erythrocytes as well as water content in the myocardium and skeletal muscle changed significantly.

Chronic hyperhydration and hematological changes in trained subjects during prolonged restriction of motor activity

The objective of this investigation was to evaluate the effect of a daily intake of fluid and salt supplementation (FSS) on the hemoglobin content of endurance trained athletes during hypokinesia (decreased number of steps from 10,000 to 3000 steps per day). The studies were performed on 30 long-distance runners who had a VO2max average of 66 ml kg-1 min-1 and were in the age range of 19-24 years. Prior to their exposure to hypokinesia (HK) of 364 days, all volunteers were on an average of 10,000 steps per day. All volunteers were divided into three equal groups: the first group underwent normal ambulatory life (control subjects), the second group was kept under continuous restriction of motor activity (hypokinetic subjects), and the third group was placed under continuous restriction of motor activity and consumed 26 ml water kg-1 body weight daily and 0.1 g sodium chloride kg-1 body weight in the form of supplementation (hyperhydrated subjects). For simulation of the hypokinetic effect, the number of steps taken per day by the second and third groups of volunteers was restricted to an average of 3000. During the hypokinetic period we determined reticulocytes (Rt), hemoglobin (Hb), hematocrit (Hct), plasma volume (PV), red blood cell (RBC) mass and VO2max. In hyperhydrated volunteers the content of Hb and Hct decreased significantly, while PV, RBC mass and Rt count increased significantly. In hypokinetic volunteers Hb and Hct increased, while PV, RBC and Rt decreased significantly. It was concluded that chronic hyperhydration may be used to attentuate an increase in the Hb content of physically conditioned subjects during prolonged restriction of motor activity.