Dec 15, 2016 · ATP and Muscle Contraction. For thin filaments to continue to slide past thick filaments during muscle contraction, myosin heads must pull the actin at the binding sites, detach, re-cock, attach to more binding sites, pull, detach, re-cock, etc. This repeated movement is known as the cross-bridge cycle. Length of muscle fiber contraction. Because a muscle is attached to bones, muscle contraction is restricted to lengths that are between 60 percent and 175 percent of the length that produces optimal strength. This range of muscle lengths limits myosin cross bridges and actin to positions only where they overlap and thus can generate contractions. Because sarcomeres are joined end to end throughout an entire muscle fiber, their simultaneous contraction shortens the entire muscle. Figure 3-5 An illustration of a single sarcomere showing the cross-bridge structure created by the myosin heads and their attachment to the actin filaments.