The length of a sarcomere determines the degree of tension produced. For optimal contraction, the ideal range of sarcomere length is 75 percent to 130 percent of its normal length. This is because at this range, there is a maximal number of that can be formed during contraction.

Cross-bridges

Explanation:

A Sarcomere is the functional unit of the muscle which is composed of the myofilaments called the actin and myosin.

The actin and myosin filaments when form cross bridge that is a structure formed when the myosin binds the actin is responsible for the muscle contraction and relaxation. The muscle contracts when a power stroke is experienced after the cross-bridge formation.

The sarcomere length shortens up to 75 to 130 per cent of its normal length during contraction as the maximum number of the cross-bridges are formed between this range and cause the repeated power stroke.

Thus, cross-bridge is the correct answer.

an organism's phenotype is the  form of a trait  that it  displays. for  flowercolor, a pea  plant  can  display  a phenotype of purple or white flowers. an organism's  genotype  is the alleles of a gene it contains. based on his data, mendel concluded that a phenotype can be  determined  by more than one  genotype.