The structural explanation of how a muscle fiber contracts is called the
The skeletal muscle fibers contract when the sarcomere in the myofibrils contract. The contraction of the sarcomeres is explained by the sliding filament theory. (The word theory is used here in its scientific sense as meaning generally accepted laws and principles, as in the theory of evolution.).he plasma membrane of the skeletal muscle fiber is called a sarcolemma. The muscle fiber contains long cylindrical structures, the myofibrils. The myofibrils almost entirely fill the cell and push the nuclei to the outer edges of the cell under the sarcolemma.