Our meta analysis of a homogeneous set of studies is the first to provide valuable LLNs for fiber CSA according to fiber type and gender .
Skeletal muscle atrophy is a major systemic impairment in chronic diseases .
Yet its determinants have been hard to identify because a clear research definition has not been agreed upon .
The reduction in muscle fiber cross-sectional area ( CSA ) is a widely acknowledged marker of muscle atrophy , but no reference values for the muscle fiber CSA at the age of the onset of chronic disease have ever been published .
Muscle fiber characteristics in postmenopausal women with normal or impaired glucose tolerance.
OBJECTIVE Muscle fiber characteristics are altered in type 2 diabetes . We studied whether these alterations also exist in impaired glucose tolerance ( IGT ) and whether they are determinants of insulin sensitivity and glucose tolerance in postmenopausal women . RESEARCH DESIGN AND METHODS Percutaneous muscle biopsies from the vastus lateralis muscle were obtained from 77 postmenopausal women aged 57 - 59 years : 50 women with normal glucose tolerance ( NGT ) and 27 with IGT .  The IGT group had a reduced insulin sensitivity compared with the NGT group ( euglycemic-hyperinsulinemic clamp ) ( P = 0.003 ) . RESULTS The groups did not differ in muscle fiber composition , as judged by the percentage of type I , IIa , or IIx fibers . In contrast , the IGT group had increased size of the IIa ( mean + /-SD 3,776+/-987 vs. 3,078+/-862 microm2 , P = 0.002 ) and IIx fibers ( 2,730+/-1,037 vs. 2,253+/-672 microm2 , P = 0.017 ) . There was a trend for the capillary diffusion areas ( the muscle area supplied by each capillary ) to be larger in the IGT group for the IIa ( 1,132+/-286 vs. 1,013+/-240 microm2 , P = 0.061 ) and IIx fibers ( 1,020+/-246 vs. 906+/-240 microm2 , P = 0.058 ) . In the entire group , insulin sensitivity correlated with the size of the type IIa fibers ( r = -0.28 , P = 0.013 ) , but not with the percentages of muscle fiber types . In a multiple regression , insulin sensitivity was determined by body fat content and HDL cholesterol level , while the size of the IIa fibers was not included in the model . Glucose tolerance was independently predicted by the number of capillaries/type I fiber , as well as by insulin sensitivity and triglyceride levels . CONCLUSIONS We conclude that although muscle fiber composition is not altered , women with IGT have larger type IIa and IIx muscle fibers and a trend for increased capillary diffusion areas for these fibers , compared with women with NGT . In the entire group , insulin sensitivity was determined mainly by body fat content , while muscle fiber capillarization may be of importance for glucose tolerance
Our meta analysis of a homogeneous set of studies is the first to provide valuable LLNs for fiber CSA according to fiber type and gender .
Skeletal muscle atrophy is a major systemic impairment in chronic diseases .
Yet its determinants have been hard to identify because a clear research definition has not been agreed upon .
The reduction in muscle fiber cross-sectional area ( CSA ) is a widely acknowledged marker of muscle atrophy , but no reference values for the muscle fiber CSA at the age of the onset of chronic disease have ever been published .