Characteristics of muscle fiber type are predictive of skeletal muscle mass and strength in elderly men.
OBJECTIVE
To investigate the relationship between skeletal muscle fiber type-specific characteristics, circulating hormone concentrations, and skeletal muscle mass and strength in older men.


METHODS
Cross-sectional analyses.


METHODS
University research center.


METHODS
Forty-one community dwelling elderly men (≥ 65).


METHODS
Leg strength (1-repetition maximum, 1RM) and whole-body and limb muscle mass were determined, and muscle fiber type composition, cross-sectional area (CSA), myonuclear content, and satellite cell (SC) content were assessed in skeletal muscle biopsy samples. In addition, blood samples were collected to determine serum testosterone, sex hormone-binding globulin, insulinlike growth factor (IGF)-1, and IGF binding protein-3 concentrations.


RESULTS
Muscle mass correlated with muscle strength (0.41 ≤ correlation coefficient (r) ≤ 0.72; P < .01). Muscle fiber CSA, myonuclear content, and SC content were significantly lower in type II than in type I muscle fibers. Myonuclear and SC content were positively correlated with muscle fiber CSA. Furthermore, greater muscle fiber CSA (type I and II) was associated with greater thigh muscle area and muscle strength (0.30 ≤ r ≤ 0.45; P < .05). Testosterone concentration was positively correlated with muscle mass and muscle fiber CSA. Regression analysis showed that SC content, myonuclear content, and testosterone concentration are predictive of muscle fiber CSA. Furthermore, muscle mass and type II muscle fiber CSA are predictive of muscle strength.


CONCLUSIONS
Skeletal muscle mass and strength in elderly men are positively correlated with muscle fiber type-specific CSA, myonuclear content, and SC content. These findings support the assumption that a decline in SC content plays an important role in age-related decline in muscle mass and strength.
Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands. Lex.Verdijk@bw.unimaas.nl
Lex B
LB
Verdijk
Tim
T
Snijders
Milou
M
Beelen
Hans H C M
HH
Savelberg
Kenneth
K
Meijer
Harm
H
Kuipers
Luc J C
LJ
Van Loon
D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D006728:Hormones / Q000097:blood; D006801:Humans; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000473:pathology*; D053580:Muscle Strength; D011379:Prognosis; D055948:Sarcopenia / Q000097:blood / Q000473:pathology* / Q000503:physiopathology
D006728:Hormones