title: Does resistance exercise prevent body fluid changes after a 90-day bed rest?
abstract: Although various exercise regimens are commonly used as countermeasures to reduce the cardiovascular deconditioning induced by microgravity, the underlying mechanisms are not well understood. In this study we aimed to test whether lower limb resistance exercise with flywheel technology can prevent the fluid homeostasis alterations induced by 90-day head-down tilt bed-rest (HDT), and thus improve orthostatic tolerance. Total body water (TBW, measured by isotope dilution) and plasma volume (PV, calculated from the haemoglobin and the haematocrit) were measured in a control group (Co, n=9) and a countermeasure group (CM, n=9). Simultaneously, plasma atrial natriuretic peptide (ANP), renin (AR), and aldosterone (Aldo), as well as urinary anti-diuretic hormone (ADH), were measured. Orthostatic tolerance was evaluated with a 10 min +80 degrees tilt-test the first day of recovery. After HDT, both groups showed a comparable decrease in orthostatic tolerance [8.2 (0.9) min, Co; 8.0 (0.7) min, CM], PV [-4.7 (1.8)%, Co; -6.2 (2.5)%, CM, P<0.05] and TBW [-6.3 (5.4)%, Co; -3.7 (2.1)%, CM, P<0.05]. AR [97.4 (22.0)%, Co; 117.3 (26.4)%, CM] and Aldo [111.3 (58.4)%, Co; 100.6 (52.0)%, CM] increased significantly in both groups but the countermeasures produced no noticeable effects [data are expressed as mean (SE)]. The drop in ANP was also similar in both groups [-42.0 (15.2)%, Co; -51.1 (27.7)% for the CM]. Surprisingly, urinary ADH declined similarly in both groups during the basal data control period [-25.3 (5.2)%, Co; -26.1 (9.6)%, CM) and was sustained at this level during the 90-day HDT. These results show that, under the conditions described, the flywheel exercise device failed to improve characteristic manifestations of cardiovascular deconditioning and suggest that more frequent and powerful exercise, associated with another device (e.g. LBNP) might be a better countermeasure.
authors.affiliation: Laboratoire de Physiologie de l'Environnement, Faculté de Médecine, Lyon Grange-Blanche, 8 Avenue Rockefeller, 69373, Lyon, Cedex 08, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Belin de Chantemele
authors.forename: Stéphane
authors.initials: S
authors.lastname: Blanc
authors.forename: Natacha
authors.initials: N
authors.lastname: Pellet
authors.forename: Monique
authors.initials: M
authors.lastname: Duvareille
authors.forename: Guido
authors.initials: G
authors.lastname: Ferretti
authors.forename: Guillemette
authors.initials: G
authors.lastname: Gauquelin-Koch
authors.forename: Claude
authors.initials: C
authors.lastname: Gharib
authors.forename: Marc-Antoine
authors.initials: MA
authors.lastname: Custaud
mesh_terms: D000328:Adult; D000450:Aldosterone / Q000097:blood; D001510:Bed Rest; D001772:Blood Cell Count; D001794:Blood Pressure / Q000502:physiology; D001810:Blood Volume / Q000502:physiology; D001826:Body Fluids / Q000502:physiology*; D015992:Body Mass Index; D001834:Body Water / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D004906:Erythrocyte Count; D006339:Heart Rate / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology; D008297:Male; D010809:Physical Fitness / Q000502:physiology*; D010953:Plasma Volume / Q000502:physiology; D012083:Renin / Q000097:blood; D012146:Rest / Q000502:physiology*; D014563:Urodynamics / Q000502:physiology; D014667:Vasopressins / Q000652:urine; D014882:Water-Electrolyte Balance / Q000502:physiology; D018544:Weightlessness Countermeasures
chemical_list: D006454:Hemoglobins; D014667:Vasopressins; D000450:Aldosterone; D012083:Renin