A champion weight lifter picks up a pencil. A minute later she picks up a sixty-pound object using the same muscles. What was different about the two movements?
Also, what are the differences (at the cellular and molecular levels) in her arm muscles as compared to those of a weaker, untrained person?
What will be an ideal response?
The movement of the heavier object involved recruitment of more motor units. Those units were able to do the job because her resistance training exercise stimulated the hypertrophy of skeletal muscle cells; that is, individual cells contain more myofibrils and are capable of generating more tension during contraction. (One might also discuss the possibility that she has more powerful fast-twitch fibers and perhaps a few more muscle cells than nonathletic peers.)
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Answer the following statement true (T) or false (F)