Abstract

The purpose of this study was to determine the effects of bedrest-induced deconditioning on changes in 02 uptake (VO2) kinetics, 02 deficit, steadystate VO2, and recovery VO2 during the performance of constant-load exercise. Five male subjects (36-40 yr) underwent 7 days of continuous bed rest (BR) in the head-down (-6 degrees) position. Two days before (pre) and the day after (post) BR each subject performed one submaximal exercise test in the supine and one in the upright position consisting of 5 min of rest, 5 min of cycle ergometer exercise at 700 kg/m/min, and 10 min recovery from exercise. VO2 was measured continuously in all tests. Following BR steady-state VO2 was unchanged in supine and upright exercise. In the supine position BR did not change total exercise VO2, O2 deficit, or total recovery VO2. However, compared with pre-BR, total exercise VO2 decreased, O2 deficit increased, and total recovery VO2 increased during the post-BR upright test. Bedrest-induced deconditioning resulted in a reduction of total VO2 capacity and an increase in the 02 deficit during submaximal constant-load exercise. This change in VO2 kinetics is found only with exercise in the upright rather than supine position implicating orthostatic mechanism in the delayed response to submaximal exercise. Verf.-Referat