I do not see the statement - but the act of muscle contractions has to do with two proteins, the actin and myosin. The contraction takes place at the neuromuscular junction which is where the nerve and the muscle meet. Essentially, the actin moves and calcium comes down which exposes the myosin head and the actin the meets with the myosin head creating a cross bridge and there you have your contraction.
Hope that helps! Let me know if it needs to be more detailed.
