Item #1 of 10

Dynamic contraction of muscles _____________________.

is caused by the shortening of extrafusal muscle fibers;
is caused by the shortening of intrafusal muscle fibers;
may cause either flexion or extension;
both alternatives a and c are correct;
both alternatives b and c are correct;

INCORRECT - Intrafusal muscle fibers are involved in maintaining muscle tone, not in causing dynamic contraction.

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