Magnesium deposition and depletion in magnesium supplemented rats during and after hypokinesia and vivarium control

Hypokinesia (diminished movement) induces significant magnesium (Mg) changes; however, little is known about Mg deposition and Mg depletion during HK. Measuring the Mg level in some tissues during HK and post-HK and Mg supplement, we aimed to establish Mg deposition and Mg depletion during prolonged HK. Studies were done on 408, 13-wk-old male Wistar rats (370-390 g) for a 15-d pre-HK period, a 98-d HK period, and a 15-d post-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). Both UHKR and SHKR were kept in small individual cages. The SVCR and SHKR took 53 mg Mg/d. During the HK period, plasma, urinary, and fecal Mg levels increased significantly (p < or = 0.05), whereas during the post-HK period Mg deposition, muscle and bone Mg content decreased significantly (p < or = 0.05) in UHKR and SHKR when compared with their pre-HK values and their respective vivarium controls (UVCR and SVCR). During the initial days of the post-HK period, plasma, urinary, and fecal Mg levels decreased significantly (p < or = 0.05), whereas during the post-HK period Mg deposition, muscle and bone Mg content remained significantly (p < or = 0.05) depressed in UHKR and SHKR when compared with UVCR and SVCR, respectively. However, during the HK period and post-HK period Mg deposition, bone, muscle, plasma, urinary, and fecal Mg levels changed significantly (p < or = 0.05) more in SHKR than UHKR. By contrast, during the HK period and post-HK period. Mg deposition, muscle, bone, plasma, urinary, and fecal Mg values change insignificantly (p > 0.05) in UVCR and SVCR when compared with their pre-HK values. It was concluded that reduced muscle, bone, plasma, urinary, and fecal Mg during post-HK and Mg supplement may demonstrate Mg depletion, whereas higher Mg loss during HK despite reduced muscle and bone Mg and Mg depletion might demonstrate Mg deposition incapacity during HK.

Fluid and salt supplementation effect on body hydration and electrolyte homeostasis during bed rest and ambulation

Bed rest (BR) induces significant urinary and blood electrolyte changes, but little is known about the effect of fluid and salt supplements (FSS) on catabolism, hydration and electrolytes. The aim was to measure the effect of FSS on catabolism, body hydration and electrolytes during BR. Studies were done during 7 days of a pre-bed rest period and during 30 days of a rigorous bed rest period. Thirty male athletes aged, 24.6 +/- 7.6 years were chosen as subjects. They were divided into three groups: unsupplemented ambulatory control subjects (UACS), unsupplemented bed rested subjects (UBRS) and supplemented bed rested subjects (SBRS). The UBRS and SBRS groups were kept under a rigorous bed rest regime for 30 days. The SBRS daily took 30 ml water per kg body weight and 0.1 sodium chloride per kg bodyweight. Plasma sodium (Na), potassium (K), calcium (Ca) and magnesium (Mg) levels, urinary Na, K, Ca and Mg excretion, plasma osmolality, plasma protein level, whole blood hemoglobin (Hb) and hematocrit (Hct) level increased significantly (p < or = 0.05), while plasma volume (PV), body weight, body fat, peak oxygen uptake, food and fluid intake decreased significantly (p < or = 0.05) in the UBRS group when compared with the SBRS and UACS groups. In contrast, plasma and urinary electrolytes, osmolality, protein level, whole blood Hct and Hb level decreased significantly (p < or = 0.05), while PV, fluid intake, body weight and peak oxygen uptake increased significantly (p < or = 0.05) in the SBRS group when compared with the UBRS group. The measured parameters did not change significantly in the UACS group when compared with their baseline control values. The data indicate that FSS stabilizes electrolytes and body hydration during BR, while BR alone induces significant changes in electrolytes and body hydration. We conclude that FSS may be used to prevent catabolism and normalize body hydration status and electrolyte values during BR.

Effect of fluid and salt supplementation on body hydration of athletes during prolonged hypokinesia

Body hydration decreases significantly during hypokinesia (HK) (diminished movement), but little is known about the effect of fluid and salt supplements (FSS) on body hydration during HK. The aim of this study was to measure the effect of FSS on body hydration during HK. Studies were done during 30 days pre HK period and 364 days HK period. Thirty male athletes aged 24.5 +/- 6.6 yr were chosen as subjects. They were equally divided into three groups: unsupplemented ambulatory control subjects (UACS), unsupplemented hypokinetic subjects (UHKS) and supplemented hypokinetic subjects (SHKS). Hypokinetic subjects were limited to an average walking distance of 0.7 km day-1. The SHKS group took daily 30 ml of water/kg body weight and 0.1 g of sodium chloride (NaCl)/kg body weight. Control subjects experienced no changes in their professional training and routine daily activities. Plasma volume (PV), urinary and plasma sodium (Na) and potassium (K), plasma osmolality, plasma protein, whole blood hemoglobin (Hb) and hematocrit (Hct), plasma renin activity (PRA) plasma aldosterone (PA) levels, physical characteristics, food and fluid intakes were measured. Plasma osmolality, plasma protein, urinary and plasma Na and K, whole blood Hct and Hb, PRA and PA levels decreased significantly (p < or = 0.01), while PV and body weight increased significantly (p < or = 0.01) in the SHKS group when compared with the UHKS group and did not change when compared with the UACS group. Plasma osmolality, plasma protein, urinary and plasma Na and K, PRA and PA, whole blood Hb and Hct levels increased significantly (p < or = 0.01), while PV body weight, food and fluid intakes decreased significantly (p < or = 0.01) in UHKS group when compared with the SHKS and UACS groups. The measured parameters did not change in the UACS group when compared with their baseline control values. It was shown that during HK body hydration decreased significantly, while during HK and FSS body hydration increased significantly. It was concluded that daily intake of FSS prevents the decrease of PV and blunts the increase of activity of the PRA and PA during prolonged HK.

Phosphate deposition capacity of athletes during hypokinesia, phosphate loading, and ambulation

Hypokinesia (diminished movement) induces significant phosphate (P) excretion; however, little is known about the P deposition ability of the body during hypokinesia (HK). Using P loads, the aim of this study was to establish the deposition ability of the body to retain P during prolonged HK. Studies were done during a 30-d period of pre-HK and a 364-d period of HK. Forty male trained athletes aged 24.7 +/- 8.0 yr were chosen as subjects. They were equally divided into four groups: unloaded ambulatory control subjects (UACS), unloaded hypokinetic subjects (UHKS), loaded ambulatory control subjects (LACS), and loaded hypokinetic subjects (LHKS). All hypokinetic subjects were limited to an average walking distance of 0.7 km/d. Loading tests with 85.0 mg of calcium phosphate/kg body weight were performed on the LACS and LHKS. Fecal P loss, urinary calcium (Ca) and P loss, serum P, Ca, and the ionized calcium (CaI) levels increased significantly (p < or = 0.05) in the LHKS and UHKS groups when compared with the LACS and UACS groups, respectively. Serum intact parathyroid hormone (iPTH) and the 1,25-dihydroxyvitamin D3 [1,25-(OH)2 D3] levels decreased significantly (p < or = 0.05) in the LHKS and UHKS groups when compared with the LACS and UACS groups, respectively. After the P load, significant (p < or = 0.05) differences were observed between LHKS and UHKS groups regarding serum, urinary, and fecal P changes. Thus, the deposition capacity of P decreased significantly (p < or = 0.05) more in the LHKS group than in the UHKS group. The deposition of P, fecal P, urinary P and Ca, serum CaI, P, Ca, 1,25-(OH)2 D3, and iPTH changed insignificantly (p > 0.05) in control groups when compared with their baseline values. It was shown that after the P load, significant differences were observed between the loaded and unloaded hypokinetic subjects regarding serum, urinary, and fecal P values and P retention. The oral P load intensified P loss from the body. It was concluded that the higher the P intake increased the greater P loss and the lower P deposition and thus the less likely it is for the P load to benefit hypokinetic subjects.

Measurements in potassium-supplemented athletes during and after hypokinetic and ambulatory conditions

Hypokinesia (diminished movement) induces significant potassium (K) changes; however, little is known about K deposition and deficiency during hypokinesia (HK). Using K supplements during and after HK, the aim was to establish body K deposition and K deficiency during HK. Studies were done during the pre-HK period of 30 d, HK period of 364 d, and post-HK period of 30 d. Forty male trained athletes aged 24.9 +/- 8.0 y were chosen as subjects. They 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). Hypokinetic subjects were limited to an average walking distance of 0.7 km/d. Control subjects ran an average distance of 11.6 km/d. The SHKS and SACS groups took 95.0 mg elemental K/kg body weight daily. Fecal K excretion, urinary sodium (Na) and K excretion, plasma K and Na levels, plasma renin activity (PRA), plasma aldosterone (PA), food and fluid intake, and physical characteristics were measured. During HK, fecal K loss, urinary K and Na loss, and plasma K, Na, PRA, and PA levels increased significantly (p < or = 0.05), whereas during the initial days of post-HK, the levels of the measured parameters decreased significantly (p < or = 0.05) in the SHKS and UHKS groups as compared with the SACS and UACS groups, respectively. During HK, body weight, body fat, peak oxygen uptake, food and fluid intake decreased significantly (p < or = 0.05), whereas during the initial days of post-HK period remained significantly (p < or = 0.05) depressed and fluid intake increased in SHKS and UHKS groups when compared with the SACS and UACS groups, respectively. However, during HK and post-HK plasma, urinary, and fecal K changed significantly (p < or = 0.05) more in the SHKS group than in the UHKS group. The deposition of K was significantly (p < or = 0.05) lower and K deficiency much higher in the SHKS group than in the UHKS group. Fecal K loss, urinary K and Na loss, plasma K, Na, PRA, and PA levels, body weight, body fat, peak oxygen uptake, and food and fluid intake did not change significantly in the SACS and UACS when compared with their baseline control values. It was shown that plasma K concentration and urinary and fecal K excretion increased during HK and decreased significantly (p < or = 0.05) during post-HK. Oral K supplements did not influence plasma or fecal and urinary K either during HK or post-HK. It was concluded that the low plasma K level and fecal and urinary K loss during post-HK may indicate the presence of K deficiency, and increased K in plasma, urine, and feces during HK and in the presence of K deficiency may suggest the body's inability to retain K 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.

Effect of prolonged restriction of motor activity on primates hydration homeostasis

It has been assumed that restriction of motor activity (hypokinesia) induces significant changes in body hydration homeostasis. Thus, the objective of this study was to measure body hydration level during prolonged hypokinesia (HK). The studies were done on 12 male Macaca Mulatta (rhesus monkeys) aged three to five years (4.75 to 6.96 kg) during a 15-day period of pre HK and a 90-day period of HK. All primates were divided equally into two groups: monkeys placed under vivarium conditions served as vivarium control primates (VCP) and monkeys subjected to HK served as hypokinetic primates (HKP). For simulation of the HK effect, the HKM group was kept for 90 days in small individual cages that restricted their movements in all directions without hindering food and water intakes. During the pre HK period of 15 days and the HK period of 90 days the following parameters were measured: total body water (TBW), extracellular fluid volume (EFV), intracellular fluid volume (IFV), circulating plasma volume (CPV) and interstitial fluid volume (IsFV), urinary and plasma sodium and potassium, fluid consumption and elimination in urine, and body weight. Significant (p < or = 0.01) decrease in the TBW, IFV, and CPV was observed in the HKP group when compared with the VCP group. In the HKP group EFV and IsFV decreased significantly (p < or = 0.01) when compared with the VCP group only in the initial seven days of the HK period, while after the 7th day progressive increase could be observed. Fluid loss, urinary electrolyte excretion and plasma electrolyte concentration increased significantly (p < or = 0.01), while fluid intakes decreased significantly (p < or = 0.01) in the HKP group when compared with the VCP group. In the HKP group body weight decreased significantly (p < or = 0.01) when compared with the VCP group. In the VCP group the measured parameters did not change significantly when compared with the baseline control values. It was concluded that prolonged exposure to HK induces significant changes in body hydration homeostasis while body dehydration in monkeys caused primarily due to decreased CPV.

Electrolyte changes in plasma and urine of athletes during acute and rigorous bed rest and ambulatory conditions

Rigorous bed rest (RBR) induces significant electrolyte changes, but little it is not known about the effect of acute bed rest (ABR) (i.e., abrupt confinement to a RBR). The aim of this study was to measure urinary and plasma electrolyte changes during ABR and RBR conditions. The studies were done during 3 d of a pre-bed-rest (BR) period and during 7 d of an ABR and RBR period. Thirty male trained athletes aged, 24.4 +/- 6.6 yr were chosen as subjects. They were divided equally into three groups: unrestricted ambulatory control subjects (UACS), acute-bed-rested subjects (ABRS), and rigorous-bed-rested subjects (RBRS). The UACS group experienced no changes in professional training and daily activities. The ABRS were submitted abruptly to a RBR regimen and without having any prior knowledge of the exact date and time when they would be subjected to an RBR regimen. The RBRS were subjected to an RBR regime on a predetermined date and time known to them from the beginning of the study. Sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), and phosphate (P) in plasma and urine, plasma renin activity (PRA) and plasma aldosterone (PA), physical characteristics, peak oxygen uptake, and food and water intakes were measured. Urinary Na, K, Ca, Mg, and P excretion and plasma Na, K, Mg, Ca, and P concentration, PRA, and PA concentration increased significantly (p < or = 0.01), whereas body weight, peak oxygen uptake, and food and water intakes decreased significantly in the ABRS and RBRS groups when compared with the UACS group. However, urinary and plasma Na, K, Mg, P, and Ca, PRA, and PA values increased much faster and were much greater in the ABRS group than in the RBRS group. Plasma and urinary Na, K, Ca, Mg, and P, PRA and PA levels, food and water intakes, body weight, and peak oxygen uptake did not change significantly in the UACS group when compared with its baseline control values. It was shown that RBR and ABR conditions induce significant increases in urinary and plasma electrolytes; however, urinary and plasma electrolyte changes appeared much faster and were much greater in the ABRS group than the RBRS group. It was concluded that the more abruptly motor activity is ended, the faster and the greater the urinary and plasma electrolyte change.

Electrolytes in femur and plasma of rats during prolonged restriction of motor activity

Hypokinesia (decreased motor activity) induces insignificant bone mineral changes. The aim of this study was to measure mineralization, density, and also electrolyte content in the femur of rats during prolonged hypokinesia (HK). Studies were done on 144 male Wistar rats (370-390 g) during 15 days period of pre-HK and 90 days period of HK. Rats were equally divided into two groups: hypokinetic rats (HKR) and vivarium control (VCR). The HKR group of rats was kept in small individual cages. Femur mineralization density, ash mineral content, calcium (Ca) and phosphate (P) content, and plasma Ca and P concentration were measured. In the HKR group body weight, femur mineralization, density, ash mineral content, Ca and P concentration decreased significantly (p < or = 0.01) while plasma Ca and P concentration increased significantly (p < or = 0.01) when compared with the VCR group. The measured parameters did not change significantly in the VCR group when compared with the baseline control values. It was concluded that prolonged HK induces a significant reduction in electrolyte concentration accompanied by decreased mineralization, density, and ash mineral content of the femur of rats.

Calcium measurements in primates during and after hypokinesia in establishing calcium deficiency during prolonged hypokinesia

Hypokinesia (diminished movement) induces significant calcium (Ca) changes, but little is known about the effect of hypokinesia (HK) on Ca deficiency. Measuring Ca changes during and after HK the aim of this study was to determine Ca deficiency during prolonged HK. Studies were done on 12 male Macaca mulatta (rhesus monkeys) aged 3-5 yr (5.58-6.42 kg) during a 90-d pre-HK period, a 90-d HK period, and a 15-d post-HK period. Monkeys were equally divided into two groups: vivarium control monkeys (VCM) and hypokinetic monkeys (HKM). Hypokinetic monkeys were kept in small individual cages that restricted their movements in all directions without hindering food and water intakes. Urinary, fecal, and serum Ca, urinary and serum magnesium (Mg) and phosphate (P), serum intact parathyroid hormone (iPTH), and calcitonin (CT) concentration, body weight, food intake, fluid consumed and eliminated in urine were measured. During the HK period, fecal Ca loss, urinary Ca, P, and Mg excretion, fluid elimination, and serum P, Ca, and Mg concentration increased significantly (p < or = 0.01), whereas serum iPTH and CT concentration, food and fluid intakes, and body weight decreased significantly (p < or = 0.01) in the HKM group when compared with the VCM group. During the initial days of the post-HK period, serum Ca, Mg, and P concentration, fecal Ca loss, urinary Ca, Mg, and P excretion, and fluid elimination decreased significantly (p < or = 0.01), whereas fluid intake increased significantly (p < or = 0.01) in the HKM group when compared with the VCM group. Food intake, body weight, and serum iPTH and CT concentrations remained significantly (p < or = 0.01) depressed in the HKP group when compared with the VCM; however, they increased as the duration of the post-HK period increased. By contrast, the corresponding parameters remained stable in the VCM group when compared with the baseline control values. It was shown that fecal and urinary Ca loss and serum Ca concentration increases significantly during HK, whereas during postHK fecal, urinary, and serum Ca decreases significantly. It was concluded that significant decrease of serum, urinary, and fecal Ca during post-HK may suggest the presence of Ca deficiency during prolonged HK.

Measurements in calcium-supplemented athletes during and after hypokinetic and ambulatory conditions

STUDY OBJECTIVE

Hypokinesia (diminished movement) induces significant calcium (Ca) changes, however, little is known about Ca deficiency during hypokinesia (HK). By using Ca supplements during and after HK, the aim of this study was to establish whether HK could contribute to Ca deficiency.

DESIGN AND METHODS

Studies were done during the pre-HK period of 30 days, HK period of 364 days and post-HK period of 30 days. Forty male trained athletes aged, 25.0 +/- 7.7 yr were chosen as subjects. They were equally divided into four groups: unsupplemented ambulatory control subjects (UACS), unsupplemented hypokinetic subjects (UHKS), supplemented ambulatory control subjects (SACS), and supplemented hypokinetic subjects (SHKS). The SHKS and SACS groups took daily 55.0 mg elemental Ca per kg body weight. Hypokinetic subjects were limited to an average walking distance of 0.7 km/day, while the control subjects were running 11.6 km/day.

RESULTS

Fecal Ca, urinary Ca, and urinary phosphate (P) excretion, serum ionized calcium (Ca(I)), P and total Ca levels, intact parathyroid hormone (iPTH), 1,25 dihydroxyvitamin D (1,25(OH)(2)D(3)), fluid and food intakes, peak oxygen uptake, and physical characteristics were measured. During HK fecal Ca, urinary Ca, and urinary P excretion and serum P, Ca(I), and Ca level increased significantly (p < or = 0.01), whereas during the initial days of post-HK decreased significantly (p < or = 0.01) in the SHKS and unsupplemented hypokinetic subjects groups when compared with the SACS and UACS groups, respectively. During HK serum 1,25(OH)(2)D(3), iPTH levels, food and fluid intakes, body weight, body fat, and peak oxygen uptake decreased significantly (p < or = 0.01), while during the initial days of post-HK remained significantly (p < or = 0.01) depressed and fluid intakes increased significantly (p < or = 0.01) in the SHKS and unsupplemented hypokinetic subjects groups when compared with SACS and UACS groups, respectively. Serum, urinary and fecal Ca changed much more in the SHKS than UHKS. Serum, fecal, and urinary minerals, iPTH, 1,25(OH)(2)D(3) levels, food and fluid intakes, body weight, body fat, and peak oxygen uptake did not change markedly in the SACS and UACS groups when compared with their baseline values.

CONCLUSION

It was shown that serum Ca concentration, urinary, and fecal Ca excretion increased during HK and decreased significantly during post-HK. Oral Ca supplementation did not significantly affect serum Ca levels or urinary and fecal Ca loss. It was concluded that decreased urinary and fecal Ca loss during post-HK, may suggest the presence of Ca deficiency during prolonged HK.

Biochemical and hormonal changes in endurance trained volunteers during and after exposure to bed rest and chronic hyperhydration

The objective of this investigation was to assess the effect of a daily intake of fluid and salt supplementation on biochemical and hormonal changes in endurance trained volunteers aged 19-24 yrs during 30-day bed rest and during 15 days of post bed rest period. The studies were performed on 30 long distance runners aged 19-24 yrs who had a peak oxygen uptake of 66 ml/kg/min and had taken 14.5 km/day on 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 subjected to bed rest alone unsupplemented (bed rested volunteers); the third group was submitted to bed rest and consumed daily 30 ml water/kg bodyweight and 0.1 g of sodium chloride (NaCl)/kg body weight (supplemented bed rested volunteers). The second and third groups of volunteers were kept under a rigorous bed rest regime for 30 days. During the pre bed rest period of 15 days, during the bed rest period of 30 days and during the post bed rest period of 15 days cyclic adenosine monophosphate, cyclic guanosine monophosphate, prostaglandins of pressor, prostaglandins depressor groups, renin activity in plasma and aldosterone in plasma and in urine were determined. We found that in bed rested volunteers without fluid and salt supplementation intake plasma renin activity and aldosterone in plasma and urine continued to increase during the bed rest period as plasma volume decreased. Moreover, in this group, cyclic nucleotides measured as an indicator of adrenosympathetic system activity increased and prostaglandins as local vasoactive substances decreased during the bed rest period. These variables returned toward the baselines in the post bed rest period as plasma volume deficit was restituted. On the other hand, the hormonal levels in the other two groups remained rather constant during the experimental period. We concluded that daily intake of fluid and salt supplementation may minimize the biochemical and hormonal changes in endurance trained volunteers dorm their exposure to bed rest conditions.

Calcium supplementation effect on calcium balance in endurance-trained athletes during prolonged hypokinesia and ambulatory conditions

Calcium (Ca) supplements may be used to normalize Ca-balance changes but little is known about the effect of Ca supplements on Ca balance during hypokinesia (decreased kilometers per day). The aim of this study was to evaluate the effect of daily intakes of Ca supplements on Ca balance during hypokinesia (HK). Studies were done during 30 d of a pre-HK period and during 364 d of a HK period. Forty male athletes aged 23-26 yr were chosen as subjects. They were divided equally into four groups: unsupplemented ambulatory control subjects (UACS), unsupplemented hypokinetic subjects (UHKS), supplemented hypokinetic subjects (SHKS), and supplemented ambulatory control subjects (SACS). The SHKS and UHKS groups were kept under an average running distance of 0.7 km/d. In the SHKS and SACS groups supplemented with 35.0 mg Ca lactate/kg body weight. Fecal Ca loss, urinary excretion of Ca and phosphate (P), serum concentrations of ionized calcium (CaI) total Ca, P, and Ca balance, intact parathyroid hormone (iPTH) and 1,25 dihydroxyvitamin D (1,25(OH)2D), anthropometric characteristics and peak oxygen uptake were measured. Fecal Ca excretion, urinary Ca and P excretion, serum CaI, total Ca, and P concentration, and negative Ca balanced increased significantly (p < or = 0.01) in the SHKS and UHKS groups when compared with the SACS and UACS groups. Serum, urinary, and fecal Ca changes were much greater and appeared much faster in the SHKS group than in the UHKS group. Serum iPTH and 1,25 (OH)2 D, body weight, and peak oxygen uptake decreased significantly (p < or = 0.01) in the SHKS and UHKS groups when compared with the SACS and UACS groups. In contrast, the corresponding parameters remained stable in the SACS and UACS groups when compared with the baseline control values. It was concluded that during prolonged HK, urinary and fecal Ca excretion and serum Ca concentration increased significantly despite the presence of a negative Ca balance; thus, Ca supplements cannot be used to normalize negative Ca balance 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.

Potassium supplements' effect on potassium balance in athletes during prolonged hypokinetic and ambulatory conditions

Electrolyte supplements may be used to prevent changes in electrolyte balance during hypokinesia (diminished movement). The aim of this study was to measure the effect of potassium (K) supplements on K balance during prolonged hypokinesia (HK). Studies were done during 30 d of a pre-HK period and during 364 d of an HK period. Forty male athletes aged 25.1+/-4.4 yr were chosen as subjects. They were divided equally into four groups: unsupplemented ambulatory control subjects (UACS), unsupplemented hypokinetic subjects (UHKS), supplemented hypokinetic subjects (SHKS) and supplemented ambulatory control subjects (SACS). The SHKS and UHKS groups were kept under an average walking distance of 0.7 km/d. The SACS and SHKS groups were supplemented daily with 50.0 mg elemental potassium chloride (KCl) per kilogram body weight. The K balance, fecal K excretion, urinary K, sodium (Na), and chloride (Cl) excretion, plasma K, Na, and Cl concentration, plasma renin activity (PRA) and plasma aldosterone (PA) concentration, anthropometric characteristics and peak oxygen uptake were measured. Negative K balance, fecal K excretion, urinary K, Na, and Cl excretion, plasma K, Na, and Cl concentration, and PRA and PA concentration increased significantly (p < or = 0.01), whereas body weight and peak oxygen uptake decreased significantly in the SHKS and UHKS groups when compared with SACS and UACS groups. However, the measured parameters changed much faster and much more in SHKS group than UHKS group. By contrast, K balance, fecal, urinary, and plasma K, plasma hormones, body weight, and peak oxygen uptake did not change significantly in the SACS and UACS groups when compared with the baseline control values. It was concluded that prolonged HK induces a significant negative K balance associated with increased plasma K concentration and urinary and fecal K excretion. However, negative K balance appeared much faster and was much greater in the SHKS group than UHKS group. Thus, K supplementation was not effective in preventing negative K balance during prolonged HK.

Plasma volume and biochemical changes in athletes during bed rest chronic hyperhydration

Daily fluid and salt supplements (FSS) may be used to reduce plasma biochemical changes during bed rest (BR). The aim of this study was to evaluate the effect of a daily intake of FSS on plasma volume (PV) and biochemical changes during BR. Studies were done during a pre BR period of 15 days and during a BR period of 30 days. Thirty male athletes aged 22-26 years were chosen as subjects. They were divided into three groups: unsupplemented ambulatory control subjects (UACS), unsupplemented bed rested subjects (UBRS) and supplemented bed rested subjects (SBRS). The UBRS and SBRS were kept under a rigorous bed rest regime for 30 days. The SBRS took 26 ml water/kg body weight and 0.1 g sodium chloride/kg body weight daily. PV, protein, albumin, sodium (Na), Chloride (Cl), potassium (K), osmolality, creatinine, glucose, and whole blood haematocrit (Hct) and haemoglobin (Hb) concentrations were measured. PV increased significantly (P < or = 0.01) while plasma protein, albumin. Na, Cl, K, glucose, creatinine, osmolality, and whole blood Hb and Hct concentration decreased significantly (P < or = 0.01) in the SBRS group when compared with the UBRS group. By contrast, PV decreased significantly (P < or = 0.01), while plasma protein, albumin, Na, Cl, K, glucose, creatinine, osmolality and whole blood Hct and Hb concentration increased significantly (P < or = 0.01) in the UBRS group when compared with the SBRS and UACS groups. The measured parameters did not change significantly in the UACS group when compared with the baseline control values. It was concluded that a daily intake of FSS may be used to attenuate PV losses and biochemical changes in endurance trained athletes during bed rest.

Potassium loading effect on potassium balance in athletes during prolonged restriction of muscular activity

Negative potassium balance during hypokinesia (decreased number of kilometers taken/day) is not based on the potassium shortage in the diet, but on the impossibility of the body to retain potassium. To assess this hypothesis, we study the effect of potassium loading on athletes during prolonged hypokinesia (HK). Studies were done during 30 d of a pre-HK period and during 364 d of an HK period. Forty male athletes aged 23-26 yr were chosen as subjects. They were divided equally into four groups: unloaded ambulatory control subjects (UACS), unloaded hypokinetic subjects (UHKS), loaded hypokinetic subjects (LHKS), and loaded ambulatory control subjects (LACS). For the simulation of the hypokinetic effect, the LHKS and UHKS groups were kept under an average running distance of 1.7 km/d. In the LACS and LHKS groups, potassium loading tests were done by administering 95.35 mg KCl per kg body weight. During the pre-HK and HK periods and after KCl loading tests, fecal and urinary potassium excretion, sodium and chloride excretion, plasma potassium, sodium and chloride concentration, and potassium balance were measured. Plasma renin activity (PRA) and plasma aldosterone concentration was also measured. Negative potassium balance increased significantly (p < or = 0.01) in the UHKS and LHKS groups when compared with the UACS and LACS groups. Plasma electrolyte concentration, urinary electrolyte excretion, fecal potassium excretion, PRA, and PA concentration increased significantly (p < or = 0.01) in the LHKS and UHKS groups when compared with LACS and UACS groups. Urinary and fecal potassium excretion increased much more and much faster in the LHKS group than in the UHKS group. By contrast, the corresponding parameters change insignificantly in the UACS and LACS groups when compared with the base line control values. It was concluded that urinary and fecal potassium excretion increased significantly despite the presence of negative potassium balance; thus, negative potassium balance may not be based on potassium shortage in the diet because of the impossibility of the body to retain potassium during HK.

Physiological effects of acute and ordinary bed rest conditions on endurance trained volunteers

The aim of this study was to carry out a comparative study of water balance and water protein composition of the blood during exposure to acute (abrupt restriction of motor activity) and ordinary rigorous bed rest of 7 days. The studies were performed on 30 long distance runners aged 22-25 years old who had a VO2, max of 66 ml kg-1 min-1 on the average. The volunteers were divided into three equal groups: the volunteers in the 1st group were under a normal ambulatory life conditions (control subjects), the volunteers of the 2nd group subjected to an acute bed rest (abrupt restriction of motor activity) regime (acute bed rested subjects) and the volunteers of the 3rd group were submitted to ordinary and rigorous bed rest (rigorous bed rested subjects). All volunteers were on an average of 13.8 km day before taking part in this investigation. The 2nd and 3rd groups of volunteers were kept under a rigorous bed rest regime for 7 days. During the prebed rest period and actual bed rest period plasma volume (PV), total protein and protein fractions (albumins and globulins) and hematocrit were measured. Exposure to acute bed rest conditions induced a significant increase in hematocrit, hemoglobin concentration, protein fractions and marked decrease in (PV) and water balance which were significantly more pronounced than during exposure to ordinary rigorous bed rest. It was concluded that exposure to acute bed rest conditions induces significantly greater changes in water balance and water protein concentration of the blood of endurance trained volunteers than exposure to ordinary rigorous bed rest conditions.

Daily copper supplement effects on copper balance in trained subjects during prolonged restriction of muscular activity

The aim of this study was to assess the effect of a daily intake of copper supplements on negative copper balance during prolonged exposure to hypokinesia (decreased number of kilometers per day). During hypokinesia (HK), negative copper balance is shown by increased, not by decreased, serum copper concentration, as it happens in other situations. Studies were done during a 30-d prehypokinetic period and a 364-d hypokinetic period. Forty male trained volunteers aged 22-26 yr with a peak oxygen uptake of 66.4 mL/min/kg and with an average of 13.7 km/d running distance were chosen as subjects. They were equally divided into four groups: unsupplemented ambulatory control subjects (UACS), unsupplemented hypokinetic subjects (UHKS), supplemented hypokinetic subjects (SHKS), and supplemented ambulatory control subjects (SACS). The SACS and SHKS groups took 0.09 mg copper carbonate/kg body weight daily. The SHKS and UHKS groups were maintained under an average running distance of 1.7 km/d, whereas the SACS and UACS groups did not experience any modifications in their normal training routines. During the 30-d prehypokinetic period and the 346-d hypokinetic period, urinary excretion of copper, calcium, and magnesium and serum concentrations of copper, calcium, and magnesium were measured. Copper loss in feces and copper balance was also determined. In both UHKS and SHKS groups, urinary excretion of copper, calcium, and magnesium and concentrations of copper, magnesium, and calcium in serum increased significantly when compared with the SACS and UACS groups. Loss of copper in feces was also increased significantly in the SHKS and UHKS groups when compared with the UACS and SACS groups. Throughout the study, the copper balance was negative in the SHKS and UHKS groups, whereas in the SACS and UACS groups, the copper balance was positive. It was concluded that a daily intake of copper supplements cannot be used to prevent copper deficiency shown by increased copper concentration. Copper supplements also failed to prevent negative copper balance and copper losses in feces and urine in endurance-trained subjects during prolonged exposure to HK.

Magnesium supplements' effect on magnesium balance in athletes during prolonged restriction of muscular activity

Electrolyte supplements may be used to prevent negative electrolyte balance during hypokinesia (HK) (decreased number of kilometres per day). The aim of this study was to evaluate the effect of daily intakes of magnesium (Mg) supplements on Mg balance during prolonged HK. Studies were done during a 30-day period of pre-HK and during a 364-day period of HK. Forty male athletes aged 22-26 years were chosen as subjects. They were equally divided into four groups: unsupplemented ambulatory control (UACS), unsupplemented hypokinetic subjects (UHKS), supplemented hypokinetic subjects (SHKS) and supplemented ambulatory control subjects (SACS). The SHKS and UHKS groups were maintained under an average running distance of 1.7 km/day, while the SACS and UACS groups experienced no changes in their professional training and routine daily activities. The SHKS and SACS groups took daily 23 mg Mg as Mg lactate per kilogram body weight. Mg balance, urinary and faecal Mg excretion and serum Mg concentration, anthropometric characteristics and peak oxygen uptake were measured. Negative Mg balance, faecal and urinary Mg excretion and serum Mg concentration increased significantly (p</=0.01) in the SHKS and UHKS groups when compared with the SACS and UACS groups. Serum, urinary and faecal Mg changes and negative Mg balance were much greater and appeared much faster in the SHKS group than in the UHKS group. Body weight and peak oxygen uptake decreased significantly (p</=0.01) in the SHKS and UHKS when compared with the SACS and UACS groups. By contrast, the corresponding parameters did not change significantly in the SACS and UACS groups when compared with the baseline control values. It was concluded that prolonged HK induces a significant negative Mg balance accompanied by significant Mg changes in urine, faeces and serum. Thus, using Mg supplements was not effective to prevent negative Mg balance in athletes during prolonged HK.

Calcium metabolism in bone and teeth of rats during exposure to restriction of motor activity and to swimming exercise

The effects of motor activity restriction for 90 days (hypokinesia, HK) and swimming training (T) on calcium metabolism in rat bones and teeth were evaluated. Male Wistar rats were distributed in four groups: untrained vivarium control rats (UVCR), untrained hypokinetic rats (UHKR), trained hypokinetic rats (THKR) and trained vivarium control rats (TVCR). Hypokinesia was obtained keeping the animals for 90 days in small individual cages which restricted their movements in all directions without hindering food and water intakes. Rats of THKR and TVCR were forced to swim for 15 to 90 minutes everyday. On the 1st, 7th, 15th day of a prehypokinetic period and on the 5th, 10th, 20th, 40th, 60th and 90th day of the hypokinetic period, six rats of each group were decapitated. Radioactive calcium was injected to the animals 70 days before autopsy. Calcium and phosphorus in serum, bones (molars, incisors, upper and lower jaws, parietal, scapular, clavicle, pelvic and tibial bones) and in the respective ash residues were measured. Body and bone weights, and radioactive calcium were also determined. Under prolonged exposure to HK (THKR and UHKR groups), bone weights and bone and ash Ca and P concentrations decreased, whereas serum Ca and P and 45Ca resorption increased, in comparison to the respective values in the UVCR and TVCR groups. Swimming exercise apparently did not modify calcium metabolism in the hypokinetic or control rats.

Morphometric examination of glomerulus and juxta glomerural system of rat kidney during prolonged restriction of motor activity

The aim of this study was to examine the structural changes of glomerular and juxta glomerular system (JGS) of the kidney of rats during prolonged restriction of motor activity (hypokinesia). The studies were performed during 90 days of hypokinesia (HK) on 144 male Wistar rats divided into two groups: Group one placed under ordinary vivarium conditions and serving as vivarium control rats (VCR) and Group two subjected to HK and serving as hypokinetic rats (HKR). For the simulation of the hypokinetic effect the HKR group was kept in small individual cages made of wood that restricted the movements of rats in all directions without hindering food and water intake. During a prehypokinetic period of 15 days and the hypokinetic period of 90 days, body weight and food intake were measured and morphometric examinations were done to measure the cortical and juxta medullary glomerulus on kidney sections from the VCR and HKR groups (eight rats from each group). Body weight and food intake decreased significantly in the HKR groups when compared with the VCR group. Kidney weight of rats increased, the superficial volume decreased and that of the juxta medullary glomerules increased, whereas juxta glomerular granularity indexes decreased significantly in the HKR group when compared with the VCR group. The measured parameters did not change significantly in the VCR group when compared with the baseline control values. It was concluded that prolonged exposure to HK induces a significant increase in the kidney weight and a relationship appeared between variations of the volume of cortical and juxta medullary glomerulus and the function of the juxtaglomerular apparatus.

Bone tissue changes in rats during prolonged restriction of motor activity

The objective of this investigation was to measure the effect of prolonged restriction of motor activity (hypokinesia) of rats on the mass, density, mineral composition, reconstruction parameters and elemental composition of their bone tissue. The studies were done during 90 days of hypokinesia (HK) on 90 male Wistar rats equally divided into two groups: (1) vivarium control rats (VCR) and (2) hypokinetic rats (HKR). For the simulation of the hypokinetic effect the HKR group was kept for 90 days in small individual cages made of wood that restricted the movements of rats in all directions without hindering food and water intakes. During the prehypokinetic period of 15 days and during the hypokinetic period of 90 days bone mass, bone density, bone calcium and phosphorus concentrations, bone reconstruction parameters and elemental composition of bones were determined. During the same periods food intake and body weight losses were also measured. In the HKR group signs of osteoporosis in the spongy structures of the tubular bones were observed; they also showed significant decrease in rat femur weight, and in cross section of the rat femur, and in mineral concentrations of the femoral head when compared with the VCR group. The HKR group also show a significant decrease in food intake and body weight when compared with the VCR group. The corresponding parameters did not change significantly in the VCR group when compared with the baseline control values. It was concluded that prolonged exposure to HK induced osteoporosis and structural changes in bones. This apparently occurred due to inhibition of bone tissue formation in the HKR group.