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This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 103/4/1242    most recent 00560.2007v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Trappe, S. Articles by Trappe, T. Search for Related Content PubMed PubMed Citation Articles by Trappe, S. Articles by Trappe, T.

Single muscle fiber function with concurrent exercise or nutrition countermeasures during 60 days of bed rest in women

Human Performance Laboratory, Ball State University, Muncie, Indiana

Submitted 23 May 2007 ; accepted in final form 16 July 2007

There is limited information on skeletal muscle properties in women with unloading and countermeasure programs to protect the unloading-induced atrophy. The current investigation tested the hypothesis that a concurrent aerobic and resistance exercise training program would preserve size and contractile function of slow- and fast-twitch muscle fibers. A secondary objective was to test the hypothesis that a leucine-enriched high-protein diet would partially attenuate single fiber characteristics. Vastus lateralis muscle biopsies were obtained before and on day 59 of bed rest from a control (BR; n = 8), nutrition (BRN; n = 8), or exercise (BRE; n = 8) group. Single muscle fibers were studied for diameter, peak force (P_o), contractile velocity, and power. Those in the BR group had a decrease (P < 0.05) in myosin heavy chain (MHC) I diameter (–14%), P_o (–35%), and power (–42%) and MHC IIa diameter (–16%) and P_o (–31%; P = 0.06) and an increase (P < 0.05) in MHC hybrid fibers. Changes in size and function of MHC I (–19 to –44%) and IIa (–21% to –30%) fibers and MHC distribution in BRN individuals were similar to results in the BR group. In BRE conditions, MHC I and IIa size and contractile function were preserved during bed rest. These data show that the concurrent exercise program preserved the myocellular profile of the vastus lateralis muscle during 60-day bed rest. To combat muscle atrophy and function with long-term unloading, the exercise prescription program used in this study should be considered as a viable training program for the upper leg muscles, whereas the nutritional intervention used cannot be recommended as a countermeasure for skeletal muscle.

skeletal muscle; contractile properties; microgravity; spaceflight; WISE-2005 study

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