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 oxy gen 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 s erved as ambulatory control subjects (ACS), (two) ten athletes subject ed to an acute rigorous bed rest regimen served as acute bed rested su bjects (ABRS) and (three) ten athletes submitted to a rigorous bed res t regimen served as rigorous bed rested subjects (RBRS). For the simul ation 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 th e exact date and time when they would be asked to submite to the RBR. For the simulation of the effect of RBR the RBRS group was subjected t o a rigorous bed rest regimen on a predetermined date and time known t o them right from the start of the study. During the pre bed rest peri od and during the ABR and RBR periods serum concentrations of thyroxin e (T3), triiodothyronine (T4), thyroid-stimulating hormone (TSH), chol esterol, triglycerides, total protein and albumin were measured. In th e ABRS and RBRS groups serum concentrations of T3, T4, TSH, cholestero l, triglycerides, total protein and albumin increased significantly wh en compared with the ACS group. Serum concentrations of thyroid hormon es and lipids in the ABRS group increased much faster and were more pr onounced than in the RBRS group. It is concluded that exposure to RBR and, especially, to ABR conditions induces significant increases in se rum concentrations of thyroid hormones and lipids. These changes occur red much earlier and were much greater in the ABRS group than in the R BRS group.