WISE‐2005: Adrenergic responses to 60 days of 6o head‐down bed‐rest (BR) in women with exercise counter‐measures

Abstract

Women are especially susceptible to orthostatic intolerance on return from space or after BR. Before and after 2 doses of isoproterenol (ISO) or norepinephrine (NOR) MAP, HR, cardiac output (Q), stroke volume (SV), and total peripheral resistance (TPR) were measured in 8 controls and 8 women with flywheel and lower body negative pressure treadmill exercise (EX). Pre-BR, ISO2 caused: higher HR, higher SV, higher Q, and lower TPR. NOR2 caused: lower SV, lower Q, higher TPR and higher MAP. Post-BR controls show higher baseline HR (64.9 ± 2.3 to 72.5 ± 4.8 bpm) and no increase in MAP due to NOR1. Post-BR EX show no increase of baseline HR, higher baseline TPR (18.0 ± 2.1 to 20.2 ± 2.8 mmHg/mL/min), reduced baseline Q (5.5 ± 0.5 mL/min to 4.5 ± 0.5 mL/min), reduced Q with ISO2 (Pre: 8.6 ± 0.9 mL/min; Post: 7.5 ± 0.8 mL/min), augmented TPR with NOR1 (Pre: 19.4 ± 2.2 mmHg; Post: 23.7 ± 3.3 mmHg). Controls show decreased peripheral and increased cardiac sensitivity of adrenergic receptors. EX show increased peripheral sensitivity without cardiac augmentation. We conclude that exercise is cardioprotective after exposure to 60-day BR (CSA, NASA, ESA & CNES).