Which of these bands or lines narrows when a skeletal muscle contracts?

There are three major types of muscles in human body namely; skeletal muscles, cardiac muscles and smooth muscles. Skeletal muscles is a form of striated muscle tissue which is under the voluntary control of the somatic nervous system. Most skeletal muscles are attached to bones by bundles of collagen fibers known as tendons. Their contractions pull on tendons attached to bones and if contraction of the muscle causes the muscle to shorten, the bone and thus the body part will move. During contraction band A does not narrow while I band narrows during contraction.

When a skeletal muscle contracts, the band H, and the band I narrow. In this process, the band H disappears and the band I compressed. In the band, I of the sarcomere the actin filaments that are born from the discs of Z are distinguished, where there is alpha-actinin, which is the protein that binds actin and titin.