For years, cardiovascular fitness was considered the epitome of what it meant to be healthy. Someone who could walk - or run - for miles was someone with a strong heart and lungs. That strong heart and lungs would help that person live a long and healthy life. “The heart is the most important muscle of the body” is something that exercise and medical professionals have extolled for years—but what about all the other muscles in the body? Aren’t they important as well? That answer is a resounding YES, and its causing exercise and medical professionals to rethink their paradigm around cardiovascular fitness being the most critical indicator of human health and functioning. Dependence of Cardiovascular System on Muscular Fitness At its most fundamental level, in order for the heart and the lungs to be stressed adequately to make functional improvement, muscles have to contract to move the body. The better those muscles are able to contract (that is, the better “fitness” the...