title: Comparing the effects of two in-flight aerobic exercise protocols on standing heart rates and VO(2peak) before and after space flight.
abstract: The effects of regular aerobic exercise on orthostatic tolerance have been the subject of a long-standing controversy that will influence the use of exercise during space flight. To examine these effects, astronauts performed continuous (CE) aerobic exercise (n = 8), interval (IE) aerobic exercise (n = 4), or no (NE) exercise (n = 5) during flights of 7 to 11 days. Heart rate (HR) responses to an orthostatic challenge (stand test) were measured 10 days before flight and on landing day. VO(2peak) (graded treadmill exercise) was measured 7 to 21 days before and 2 days after flight. No significant differences across the groups were observed in standing HRs before or after flight. However, the within-group mean HRs significantly increased in the NE (71-89 beats/min) and CE (60-85 beats/min) groups after space flight. The HRs for the IE group did not significantly increase (75-86 beats/min) after space flight. VO(2peak) decreased (P < .05) in the NE (-9.5%) group, but did not change in the CE (-2.4%) and IE (1%) groups. The relationship (r = 0.237) between the delta HR and delta VO(2peak) was not significant. These preliminary results indicate that: (1) continuous exercise does not affect the orthostatic HR response after space flight; (2) interval exercise may minimize an increase in the postflight orthostatic HR; and (3) both exercise protocols can maintain VO(2peak).
authors.affiliation: Space Biomedical Research Institute, NASA Johnson Space Center, Houston, Texas.
authors.forename: S F
authors.initials: SF
authors.lastname: Siconolfi
authors.forename: J B
authors.initials: JB
authors.lastname: Charles
authors.forename: A D
authors.initials: AD
authors.lastname: Moore
authors.forename: L H
authors.initials: LH
authors.lastname: Barrows
mesh_terms: D000328:Adult; D004562:Electrocardiography; D015444:Exercise; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006400:Hematocrit; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology / Q000517:prevention & control; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010806:Physical Education and Training; D013026:Space Flight