What role does calcium play in skeletal muscle contraction?
It triggers myosin actin interaction
Myosin is molecular motor protein that interacts with actin. The short version is that the basic movement of muscle contraction is the head on a myosin filament being activated by ATP and interacting with a binding site on an actin filament, which will use this movement to slide. In the absence of calcium, the myosin sites are blocked and the myosin actin interaction cannot happen, so neither can the power-stroke and neither can muscle contraction.