Achampion 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?

The heavier object motion requires more motor units being recruited.

Because of their resistance training exercise, these units were capable of doing the job, which enhanced the muscle growth of skeletal muscle cells, the individual cells with more myofibrils and are able to generate more stress during contraction.

The individual may have more quick-twitch fibers and maybe less muscle cells than a non-athletic colleague.

d, i believe because of it's activity level