There are two types of muscles, voluntary and involuntary. In order to answer this question, you need to know the difference between the two. Voluntary muscles are ones that you can control. For example, by doing a push up or waving your arms around you are using your muscles voluntarily. In contrast, involuntary muscles are ones that you cannot control. You heart contains muscle tissue that cannot be controlled voluntarily.
One example that illustrates the involuntary control of cardiac muscle tissue is the shortening in the bands of muscle in your heart, resulting in a decrease in chamber size, which then ejects blood to the pulmonary and systemic vessels.
