Key result
Eight weeks of training resulted in 7 to 11 actin fibers orbiting each myosin fiber, increased glycogen and fats, greater mitochondria length, decreased myosin density, and increased myosin diameter.
Why the study?
Do different methods of physical training alter the ultrastructure of human striated muscle in normal college males?
Do different methods of physical training alter the ultrastructure of human striated muscle in normal college males?
Eight weeks of physical training induces specific ultrastructural adaptations in human skeletal muscle, including increased mitochondria length and glycogen content.
Answers are grounded in this paper and cite their sources.
Training may induce ultrastructural remodeling in young adult skeletal muscle; leaves open functional benefits and generalizability beyond this cohort.
Skeletal muscle tissue was obtained from the vastus lateralis of six normal college male students. Two biopsies were obtained prior to, and one following the training period. Two subjects performed isotonic leg extensions, two performed isometric leg extensions, and two ran up and down stadium bleachers. All training periods lasted 8 weeks. Muscle tissue was processed immediately for electron microscope examination. The following parameters were measured from micrographs of longitudinal sections: sarcomere length, sarcomere width, A band length, I band length, intracellular fat globule quantity and diameter, mitochondria length, mitochondria quantity, and Z band width. The following parameters were measured from micrographs of cross sections: myosin fiber concentration, distance between myosin filaments, myosin filament diameter, and actin filament diameters. Observations were also made on the geometric arrangement of the filaments, glycogen, and gross myofibrillar structure. Major findings were: there are between 7 and 11 actin fibers in “orbit” around each myosin fiber, increased glycogen and intracellular fats, greater mitochondria length, decreased myosin density, and an increase in myosin fiber diameter.
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Kenneth A. Penman (1969) studied Healthy (n=6). Three methods of training (isotonic leg extensions, isometric leg extensions, running stadium bleachers) vs. Baseline (pre-training) was evaluated on Ultrastructural changes in skeletal muscle. Eight weeks of training resulted in 7 to 11 actin fibers orbiting each myosin fiber, increased glycogen and fats, greater mitochondria length, decreased myosin density, and increased myosin diameter.
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