Orthostatic reactions during recovery from exhaustive exercise of short duration

Abstract

The responses of 6 healthy volunteers to standard 70.degree. head-up tilt tests before exhaustive exercise of short duration (control) and after 5, 25, 50, 80 and 110 min of recovery (all tests lasting for 6 min except when impending syncope (IS) necessitated premature termination of a test) were studied. Marked impairment of orthostatic tolerance was apparent during the first 1/2-h of recovery as manifested by symptoms of IS in 5 subjects in 1 or both of the first 2 postexercise tilt test. In none of the subjects who developed symptoms of IS did central venous pressure fall to a lower level than it did in the control test. Form the central venous and arterial pressure reactions, when IS developed, declining systematic resistance rather than diminished cardiac filling was the responsible factor. The increased tendency for orthostatic collapse occurred during a period of recovery marked by persistent postexercise acidemia and hyperthermia, suggesting interference of these conditions and associated events with the normal ability to vasoconstrict during orthostasis.