Lower-body negative-pressure exercise and bed-rest-mediated orthostatic intolerance

被引:31
作者
Schneider, SM
Watenpaugh, DE
Lee, SMC
Ertl, AC
Williams, WJ
Ballard, RE
Hargens, AR
机构
[1] Univ New Mexico, Dept Human Performance & Dev, Johnson Ctr, Albuquerque, NM 87131 USA
[2] USN, Submarine Med Res Lab, Groton, CT USA
[3] Wyle Life Sci Inc, Houston, TX USA
[4] Vanderbilt Univ, Nashville, TN 37240 USA
[5] NASA, Ames Res Ctr, Moffett Field, CA 94035 USA
[6] Univ Calif San Diego, San Diego, CA 92103 USA
关键词
blood pressure; catecholamines; microgravity; epinephrine;
D O I
10.1097/00005768-200209000-00008
中图分类号
G8 [体育];
学科分类号
04 ; 0403 ;
摘要
Purpose: Supine, moderate exercise is ineffective in maintaining orthostatic tolerance after bed rest (BR). Our purpose was to test the hypothesis that adding an orthostatic stress during exercise would maintain orthostatic function after BR. Methods: Seven healthy men completed duplicate 15-d 6degrees head-down tilt BR using a crossover design. During one BR, subjects did not exercise (CON). During another BR, subjects exercised for 40 min(.)d(-1) on a supine treadmill against 50-60 mm Hg LBNP (EX). Exercise training consisted of an interval exercise protocol of 2- to 3-min intervals alternating between 41 and 65% VO2max. Before and after BR, an LBNP tolerance test was performed in which the LBNP chamber was decompressed in 10-mm Hg stages every 3 min until presyncope. Results: LBNP tolerance, as assessed by the cumulative stress index (CSI) decreased after BR in both the CON (830 +/- 144, pre-BR vs 524 +/- 56 mm Hg-min, post-BR) and the EX (949 +/- 118 pre-BR vs 560 +/- 44 mm Hg.min, post-BR) conditions. However, subtolerance (0 to -50 mm Hg LBNP) heart rates were lower and systolic blood pressures were better maintained after BR in the EX condition compared with CON. Conclusion: Moderate exercise performed against LBNP simulating an upright 1-g environment failed to protect orthostatic tolerance after 15 d of BR.
引用
收藏
页码:1446 / 1453
页数:8
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