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 .
Quantitative measurement of muscle fiber composition in a normal population.
To obtain normative muscle morphology data on a healthy population recruited from a population survey , we examined  vastus lateralis biopsies from 58 men and 33 women , aged 26 - 67 years .  Biopsies were measured with automated , computer-aided techniques . Data were analyzed according to gender and age , and the influence of blood pressure , body mass index ( BMI ) , and smoking habits was also examined . Men had larger muscle fibers ( fiber area approximately 5400 microm(2 ) ) than women ( approximately 4000 microm(2 ) , P = 0.003 ) . No gender differences were seen in fiber composition , fiber roundness , percentage of connective tissue , or capillary density . Blood pressure did not influence fiber size or composition , but was correlated with fiber roundness in men . BMI was associated with fiber area in men , but not in women . Variations in age , smoking habits , and physical activity did not influence muscle morphology data substantially . Thus , in a normal population , men have larger muscle fibers than women , but similar fiber composition . Variation in gender , BMI , blood pressure , and physical activity may influence morphological features to a minor degree
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 .