The correct answer is<span> shortening of the muscles. If a person doesn't move and just keeps lying down, then muscles can lose mass and eventually function. People need to be moving all the time to prevent muscle loss and shortening of muscles because things like muscle atrophy can develop and you can lose control of muscles completely.</span>
Three layers of tissue form the heart wall. The outer layer of the heart wall is the epicardium, the middle layer is the myocardium, and the inner layer is the endocardium.
