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

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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).