title: Effect of rowing ergometry and oral volume loading on cardiovascular structure and function during bed rest.
abstract: This study examined the effectiveness of a short-duration but high-intensity exercise countermeasure in combination with a novel oral volume load in preventing bed rest deconditioning and orthostatic intolerance. Bed rest reduces work capacity and orthostatic tolerance due in part to cardiac atrophy and decreased stroke volume. Twenty seven healthy subjects completed 5 wk of -6 degree head down bed rest. Eighteen were randomized to daily rowing ergometry and biweekly strength training while nine remained sedentary. Measurements included cardiac mass, invasive pressure-volume relations, maximal upright exercise capacity, and orthostatic tolerance. Before post-bed rest orthostatic tolerance and exercise testing, nine exercise subjects were given 2 days of fludrocortisone and increased salt. Sedentary bed rest led to cardiac atrophy (125 ± 23 vs. 115 ± 20 g; P < 0.001); however, exercise preserved cardiac mass (128 ± 38 vs. 137 ± 34 g; P = 0.002). Exercise training preserved left ventricular chamber compliance, whereas sedentary bed rest increased stiffness (180 ± 170%, P = 0.032). Orthostatic tolerance was preserved only when exercise was combined with volume loading (-10 ± 22%, P = 0.169) but not with exercise (-14 ± 43%, P = 0.047) or sedentary bed rest (-24 ± 26%, P = 0.035) alone. Rowing and supplemental strength training prevent cardiovascular deconditioning during prolonged bed rest. When combined with an oral volume load, orthostatic tolerance is also preserved. This combined countermeasure may be an ideal strategy for prolonged spaceflight, or patients with orthostatic intolerance.
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX 75231, USA.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Hastings
authors.forename: Felix
authors.initials: F
authors.lastname: Krainski
authors.forename: Peter G
authors.initials: PG
authors.lastname: Snell
authors.forename: Eric L
authors.initials: EL
authors.lastname: Pacini
authors.forename: Manish
authors.initials: M
authors.lastname: Jain
authors.forename: Paul S
authors.initials: PS
authors.lastname: Bhella
authors.forename: Shigeki
authors.initials: S
authors.lastname: Shibata
authors.forename: Qi
authors.initials: Q
authors.lastname: Fu
authors.forename: M Dean
authors.initials: MD
authors.lastname: Palmer
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Levine
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001284:Atrophy; D001510:Bed Rest; D006328:Cardiac Catheterization; D006332:Cardiomegaly / Q000209:etiology / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control; D018493:Cardiovascular Deconditioning / Q000187:drug effects*; D003187:Compliance; D019560:Echocardiography, Three-Dimensional; D017079:Exercise Tolerance / Q000187:drug effects; D005260:Female; D005438:Fludrocortisone / Q000008:administration & dosage*; D018475:Head-Down Tilt; D006801:Humans; D008150:Lower Body Negative Pressure; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D009206:Myocardium / Q000473:pathology; D054971:Orthostatic Intolerance / Q000209:etiology / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D010953:Plasma Volume / Q000187:drug effects*; D055070:Resistance Training; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*; D013318:Stroke Volume / Q000187:drug effects; D013781:Texas; D013997:Time Factors; D016896:Treatment Outcome; D016277:Ventricular Function, Left / Q000187:drug effects; D017725:Ventricular Pressure / Q000187:drug effects; D018544:Weightlessness Countermeasures; D055815:Young Adult
chemical_list: D017673:Sodium Chloride, Dietary; D005438:Fludrocortisone