title: Upright exercise or supine lower body negative pressure exercise maintains exercise responses after bed rest.
abstract: Adaptation to bed rest or space flight is accompanied by an impaired ability to exercise in an upright position. We hypothesized that a daily, 30-min bout of intense, interval exercise in upright posture or supine against lower body negative pressure (LBNP) would maintain upright exercise heart rate and respiratory responses after bed rest. Twenty-four men (31 +/- 3 yr) underwent 5 d of 6 degree head-down tilt: eight performed no exercise (CON), eight performed upright treadmill exercise (UPex), and eight performed supine treadmill exercise against LBNP at -51.3 +/- 0.4 mm Hg (LBNPex). Submaximal treadmill exercise responses (56, 74, and 85% of VO2peak) were measured pre- and post-bed rest. In CON, submaximal heart rate, respiratory exchange ratio, and ventilation were significantly greater (P < or = 0.05) after bed rest. In UPex and LBNPex, submaximal exercise responses were similar pre- and post-bed rest. Our results indicate that a daily 30-min bout of intense, interval upright exercise training or supine exercise training against LBNP is sufficient to maintain upright exercise responses after 5 d of bed rest. These results may have important implications for the development of exercise countermeasures during space flight.
authors.affiliation: KRUG Life Sciences, Inc., Houston, TX, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Lee
authors.forename: B S
authors.initials: BS
authors.lastname: Bennett
authors.forename: A R
authors.initials: AR
authors.lastname: Hargens
authors.forename: D E
authors.initials: DE
authors.lastname: Watenpaugh
authors.forename: R E
authors.initials: RE
authors.lastname: Ballard
authors.forename: G
authors.initials: G
authors.lastname: Murthy
authors.forename: S R
authors.initials: SR
authors.lastname: Ford
authors.forename: S M
authors.initials: SM
authors.lastname: Fortney
mesh_terms: D000328:Adult; D001510:Bed Rest; D001696:Biomechanical Phenomena; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006112:Gravitation; D006339:Heart Rate; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D011187:Posture; D012129:Respiratory Function Tests; D013026:Space Flight