MATHEMATICAL MODELING OF FUNCTIONAL STATES IN HUMANS UNDER 7-DAYS HEAD-DOWN BED REST

摘要

Changes of the functional state during long term space flights may be connected to the realignment of autonomic regulation and reinforcement of sympathetic activity and are observed quite often. We reported recently shifts of autonomic heart rate regulation in a number of ISS crew members. These changes may cause orthostatic intolerance. We tested this hypothesis under simulated microgravity conditions (7-days head-down bed rest, HDBR) in 6 volunteers (men, age 32 +-5 years). Our data suggest an initial increase of parasympathetic heart rate control followed by an increase of sympathetic influences. The final increase in sympathetic activity was more pronounced in volunteers with bad orthostatic tolerance after HDBR. The proposed mathematical model of functional state reflects the changes in autonomic balance and functional reserves under HDBR conditions. It can be proposed as a tool for forecasting orthostatic intolerance in cosmonauts.