Answers to Case Study Questions, Chapter 5, Muscular Adaptations to Training
Case Study 5.1
Michael’s muscle growth was most likely attributed to a number of factors. Because of his age,
Michael has higher testosterone concentration, which is a potent anabolic hormone. Testosterone,
and some other anabolic hormones, plays critical roles in muscle growth. The workout was
progressive to allow growth to take place. Michael had to provide consistent and progressive
loading to his exercises beyond his physiologic threshold. The loading/volume (i.e., providing
mechanical and circulatory overload) most likely led to up-regulation of muscle growth factors
and proteins modulating myogenesis to where protein synthesis was elevated, protein
degradation was lower, or some combination occurred. In particular, the ECC muscle actions
most likely provided a means to promote muscle hypertrophy. In examination of muscle fibers,
the majority of hypertrophy most likely occurred in fast-twitch muscle fibers. Diet potentially
played a critical role. Michael had maintained sufficient carbohydrate and protein intake, both of
which stimulate muscle growth. In addition, his vitamin and mineral intake was sufficient to
enhance muscle hypertrophy and allow Michael to train intensely. Lastly, muscle fiber
transitions most likely occurred. Based on the literature, Michael most likely experienced a shift
from type IIx fibers to type IIa and IIax fibers. This fiber transition could have been helpful in
improving Michael’s strength.