DIFFERENT RESISTANCE TRAINING PROTOCOLS AND SKELETAL MUSCLE FIBER HYPERTROPHY

Abstract

1180 A study was undertaken to determine which type of progressive training protocol {high resistance and low repetition (LR), moderate resistance and intermediate repetition (IR), or low resistance and high repetition (HR)} produced the greatest muscle fiber hypertrophy, and whether the nucleo-cytoplasmic (n/c) ratio was altered after hypertrophy in human male vastus lateralis muscles. Myofibrillar ATPase histochemistry was used to compare predominant fiber types, and electron microscopy was used to count myonuclei and satellite cells to determine the n/c ratio. The LR group had 18.5% fiber hypertrophy, irrespective of fiber type, while the IR group had 17.6% hypertrophy. However, while both type I and IIA were significantly larger after the LR training, only the type IIA fibers were hypertrophied in the IR group. Although the HR group hypertrophied by 12.2%, the variability between the subjects made this non-significant. The n/c ratio was unchanged in all groups, in spite of the cytoplasmic are becoming significantly larger. Satellite cell numbers and percentages (of total nuclei) did not change in any group. These data show that although type I and IIA fibers both hypertrophy in response to the various resistance programs, the type IIA appears most affected, and the LR and IR programs produce similar hypertrophy. Nuclei appear to be added to the fibers to accommodate the increased cytoplasm, since the n/c ratio remained unchanged.