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Influence of exercise and nutrition countermeasures during 60 d of bedrest in women: Vastus lateralis single muscle fiber function
Author(s) -
Creer Andrew Ryan,
Slivka Dustin,
Minchev Kiril,
Trappe Todd,
Trappe Scott
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.lb33-b
Subject(s) - chemistry , medicine , major histocompatibility complex , fiber , myosin , vastus lateralis muscle , endocrinology , anatomy , skeletal muscle , biochemistry , organic chemistry , gene
Twenty‐four women underwent 60 d of bedrest (BR, n=8) to examine the effect of a concurrent aerobic (27 sessions) and resistance (19 sessions) exercise (BRE, n=8) or a leucine enriched high protein nutrition (BRN, n=8) countermeasure. Muscle biopsies were obtained before and day 59 of bedrest. Slow (MHC I) and fast (MHC IIa) muscle fibers were studied for diameter (Dia), peak force (Po), normalized peak force (Po/CSA), contractile velocity (Vo), and MHC composition. BR had a decrease ( P <0.05) in MHC I Dia (−13%), Po (−36%), and Po/CSA (−17%). A similar trend was observed in BR MHC IIa fibers for Dia (−15%; P =0.09) and Po (−25%; P =0.14). BRN had a decrease ( P <0.05) in MHC I Dia (−18%) and Po (−38%) and MHC IIa Dia (−26%). BRN had a trend for a decrease in MHC IIa Po (−41%; P =0.10). BR and BRN MHC I and IIa Vo was unchanged. BRE MHC I and IIa fiber Dia, Po, Po/CSA, and Vo were unchanged with bedrest. These data show that the MHC I fibers were more affected than the MHC IIa fibers with bedrest. The concurrent exercise‐training program preserved MHC I and IIa diameter and contractile function during bedrest. The nutrition countermeasure did not provide any benefit for myofiber diameter or peak tension. Sponsors: NASA, ESA, CNES