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

Scott Trappe, Andrew Creer, Dustin Slivka, Kiril Minchev, Todd Trappe

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There is limited information on skeletal muscle properties in women with unloading and counter-measure 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 (Po), contractile velocity, and power. Those in the BR group had a decrease (P < 0.05) in myosin heavy chain (MHC) I diameter (-14%), Po (-35%), and power (-42%) and MHC IIa diameter (-16%) and Po (-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.

Original languageEnglish
Pages (from-to)1242-1250
Number of pages9
JournalJournal of Applied Physiology
Issue number4
StatePublished - Oct 2007


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