ABSTRACT
The main physiological adaptive feature of resistance exercise training (RET) is increased muscle mass, which manifests as an increase in the dimensions of whole muscle groups as a result of growth of individual muscles. These gross physiological changes in skeletal muscle mass are most commonly determined using imaging techniques such as dual-energy X-ray absorptiometry (DXA), computed tomography (CT), magnetic resistance imaging (MRI), or ultrasonography (43). Muscle hypertrophy can also be measured on a single-fiber level by estimation of individual myofiber cross-sectional area in biopsy samples using histological techniques coupled to imaging software analysis to determine hypertrophy on a cell-by-cell level (20). It is believed that postnatal growth of skeletal muscle occurs via the process of hypertrophy, which represents an increase in cross-sectional area of existing post-mitotic muscle cells, rather than through fiber splitting or hyperplasia (61).
