EFFECTS OF PROLONGED HEADDOWN BED REST WITH AND WITHOUT FLY-WHEEL EXERCISE ON HEART RATE VARIABILITY

摘要

The aim of this study was to investigate the effects of prolonged Head down bed rest (HDBR) (90 days) on heart rate variability (HRV) in 25 healthy male volunteers (mean age: 33 y). Nine subjects performed flywheel resistance muscular training. 24h-ECG recordings were performed in pre-HDBR (D-12, D-3), HDBR (D 15, D 32, D 62, D 85) and recovery (D+4). The mean HR, SDNN and coefficient of variation (SDNN normalized by HR) reflecting overall HRV were calculated as well as the power in Low (LF) and High (HF) frequencies (24h-period). HDBR induced a significant decrease in HRV favoured by inactivity. LF and LF/HF mainly under sympathetic influence decreased significantly on D15 and then tended to stabilise around baseline values. HF reflecting parasympathetic modulation decreased with HDBR but some changes occurred in pre-HDBR, in relation with the experiment conditions, and raised the issue of reference values. No exercise effect was observed.