We determined muscle fiber type-specific hypertrophy and changes in satellite 
cell (SC) content following a 12-week resistance training program in 13 healthy, 
elderly men (72 +/- 2 years). Leg strength and body composition (dual-energy 
X-ray absorptiometry and computed tomography) were assessed, and muscle biopsy 
samples were collected. Leg strength increased 25%-30% after training (p < 
.001). Leg lean mass and quadriceps cross-sectional area increased 6%-9% (p < 
.001). At baseline, mean fiber area and SC content were smaller in the Type II 
versus Type I muscle fibers (p < .01). Following training, Type II muscle fiber 
area increased from 5,438 +/- 319 to 6,982 +/- 503 microm(2) (p < .01). Type II 
muscle fiber SC content increased from 0.048 +/- 0.003 to 0.084 +/- 0.008 SCs 
per fiber (p < .001). No changes were observed in the Type I muscle fibers. In 
older adults, skeletal muscle tissue is still capable of inducing SC 
proliferation and differentiation, resulting in Type II muscle fiber 
hypertrophy.