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.

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.

Changes in thyroid hormones and lipids in endurance trained volunteers during acute and rigorous bed rest conditions.

The aim of this study was to evaluate the effect of an acute rigorous bed rest (ABR) (abrupt confinement to a rigorous bed rest regimen) and a rigorous bed rest (RBR) regimen on serum concentrations of thyroid hormones and lipids. The studies were done during seven days of a pre bed rest period and during seven days of an ABR and RBR period. Thirty endurance trained male volunteers aged 22 to 26 years with a peak oxygen uptake of 66.0 mL.min-1.kg-1 and running an average of 14.0 km.day-1 were chosen as subjects. They were divided equally into three groups: (one) ten athletes placed under ambulatory conditions served as ambulatory control subjects (ACS), (two) ten athletes subjected to an acute rigorous bed rest regimen served as acute bed rested subjects (ABRS) and (three) ten athletes submitted to a rigorous bed rest regimen served as rigorous bed rested subjects (RBRS). For the simulation of the effect of ABR the ABRS group was submitted abruptly to a rigorous bed rest regimen. They did not have any prior knowledge of the exact date and time when they would be asked to submit to the RBR. For the simulation of the effect of RBR the RBRS group was subjected to a rigorous bed rest regimen on a predetermined date and time known to them right from the start of the study. During the pre bed rest period and during the ABR and RBR periods serum concentrations of thyroxine (T3), triiodothyronine (T4), thyroid-stimulating hormone (TSH), cholesterol, triglycerides, total protein and albumin were measured. In the ABRS and RBRS groups serum concentrations of T3, T4, TSH, cholesterol, triglycerides, total protein and albumin increased significantly when compared with the ACS group. Serum concentrations of thyroid hormones and lipids in the ABRS group increased much faster and were more pronounced than in the RBRS group. It is concluded that exposure to RBR and, especially, to ABR conditions induces significant increases in serum concentrations of thyroid hormones and lipids. These changes occurred much earlier and were much greater in the ABRS group than in the RBRS group.