Calcium is important in skeletal muscle contraction because it

Calcium is important in skeletal muscle contraction because it binds to troponin to remove the masking of active sites on actin for myosin. At the onset of muscle contraction, the sarcoplasmic reticulum releases calcium ions ($C{a}^{++}$) into the sarcoplasm. There, they bind to troponin. Troponin then moves tropomyosin away from the myosin-binding sites on actin. Once the binding sites are “free,” the contraction cycle—the repeating sequence of events that causes the filaments to slide—begins.