Publikationsdatum:
2019-07-19
Beschreibung:
More than 60% of US astronauts participating in Mir and early International Space Station missions (greater than 5 months) were unable to complete a 10min 80 deg headup tilt test on landing day. This high incidence of postspaceflight orthostatic intolerance may be related to limitations of the inflight exercise hardware that prevented high intensity training. PURPOSE: This study sought to determine if a countermeasure program that included intense lowerbody resistive and rowing exercises designed to prevent cardiovascular and musculoskeletal deconditioning during 70 days of 6 deg head-down tilt bed rest (BR), a spaceflight analog, also would protect against post BR orthostatic intolerance. METHODS: Sixteen males participated in this study and performed no exercise (Control, n=10) or performed an intense supine exercise protocol with resistive and aerobic components (Exercise, n=6). On 3 days/week, exercise subjects performed lower body resistive exercise and a 30min continuous bout of rowing (greater than or equal to 75% max heart rate). On 3 other days/week, subjects performed only highintensity, intervalstyle rowing. Orthostatic intolerance was assessed using a 15min 80 deg headup tilt test performed 2 days (BR2) before and on the last day of BR (BR70). Plasma volume was measured using a carbon monoxide rebreathing technique on BR3 and before rising on the first recovery day (BR+0). RESULTS: Following 70 days of BR, tilt tolerance time decreased significantly in both the Control (BR2: 15.0 +/- 0.0, BR70: 9.9 +/- 4.6 min, mean +/- SD) and Exercise (BR2: 12.2 +/- 4.7, BR70: 4.9 +/- 1.9 min) subjects, but the decreased tilt tolerance time was not different between groups (Control: 34 +/- 31, Exercise: 56 +/- 16%). Plasma volume also decreased (Control: 0.56 +/- 0.40, Exercise: 0.48 +/- 0.33 L) from pre to postBR, with no differences between groups (Control: 18 +/- 11%, Exerciser: 15 +/-1 0%). CONCLUSIONS: These findings confirm previous reports in shorter BR studies that the performance of an exercise countermeasure protocol by itself during BR does not prevent orthostatic intolerance or plasma volume loss. This suggests that protection against orthostatic intolerance in astronauts following longduration spaceflight will require an additional intervention, such as periodic orthostatic stress, fluid repletion, and/or lowerbody compression garments.
Schlagwort(e):
Aerospace Medicine
Materialart:
JSC-CN-32335
,
Annual Meeting of the American College of Sports Medicine; May 26, 2015 - May 30, 2015; San Diego, CA; United States
Format:
application/pdf
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