title: Single muscle fiber function with concurrent exercise or nutrition countermeasures during 60 days of bed rest in women.
abstract: 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.
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, IN 47306, USA. strappe@bsu.edu
authors.forename: Scott
authors.initials: S
authors.lastname: Trappe
authors.forename: Andrew
authors.initials: A
authors.lastname: Creer
authors.forename: Dustin
authors.initials: D
authors.lastname: Slivka
authors.forename: Kiril
authors.initials: K
authors.lastname: Minchev
authors.forename: Todd
authors.initials: T
authors.lastname: Trappe
mesh_terms: D000328:Adult; D001510:Bed Rest; D001706:Biopsy; D004044:Dietary Proteins / Q000008:administration & dosage*; D015444:Exercise / Q000502:physiology; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D009119:Muscle Contraction; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000737:chemistry / Q000502:physiology*; D009133:Muscular Atrophy / Q000178:diet therapy / Q000517:prevention & control; D018995:Myosin Heavy Chains / Q000032:analysis; D052097:Quadriceps Muscle / Q000737:chemistry / Q000502:physiology; D013026:Space Flight
chemical_list: D004044:Dietary Proteins; D018995:Myosin Heavy Chains