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Intensive exercise training suppresses testosterone during bed restSpaceflight and prolonged bed rest (BR) alter plasma hormone levels inconsistently. This may be due, in part, to prescription of heavy exercise as a countermeasure for ameliorating the adverse effects of disuse. The initial project was to assess exercise programs to maintain aerobic performance and leg strength during BR. The present study evaluates the effect of BR and the performance of the prescribed exercise countermeasures on plasma steroid levels. In a 30-day BR study of male subjects, the efficacy of isotonic (ITE, n = 7) or isokinetic exercise (IKE, n = 7) training was evaluated in contrast to no exercise (n = 5). These exercise countermeasures protected aerobic performance and leg strength successfully. BR alone (no-exercise group) did not change steroidogenesis, as assessed by the plasma concentrations of cortisol, progesterone, aldosterone, and free (FT) and total testosterone (TT). In the exercise groups, both FT and TT were decreased (P < 0.05): FT during IKE from 24 +/- 1.7 to 18 +/- 2.0 pg/ml and during ITE from 21 +/- 1.5 to 18 +/- 1 pg/ml, and TT during IKE from 748 +/- 68 to 534 +/- 46 ng/dl and during ITE from 565 +/- 36 to 496 +/- 38 ng/dl. The effect of intensive exercise countermeasures on plasma testosterone was not associated with indexes of overtraining. The reduction in plasma testosterone associated with both the IKE and ITE countermeasures during BR supports our hypothesis that intensive exercise countermeasures may, in part, contribute to changes in plasma steroid concentrations during spaceflight.
Document ID
20050219368
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Wade, C. E.
(NASA Ames Research Center Moffett Field, CA United States)
Stanford, K. I.
Stein, T. P.
Greenleaf, J. E.
Date Acquired
August 23, 2013
Publication Date
July 1, 2005
Publication Information
Publication: Journal of applied physiology (Bethesda, Md. : 1985)
Volume: 99
Issue: 1
ISSN: 8750-7587
Subject Category
Aerospace Medicine
Distribution Limits
Public
Copyright
Other
Keywords
Clinical Trial
Controlled Clinical Trial

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