Primary Components of Fitness The four primary components (also known as the components of health related fitness) that are important to improved physical health are as follows: • Cardiorespiratory capacity is the ability of the body to take in oxygen (respiration), deliver it to the cells (circulation), and use it at the cellular level to create energy (bioenergetics) for physical work (activity). In fitness, we also refer to cardiorespiratory capacity as aerobic capacity. This capacity includes aerobic endurance (how long), aerobic strength (how hard), and aerobic power (how fast). Some of the long-term adaptations of cardiorespiratory training are: decreased resting heart rate, decreased risk of cardiovascular disease, improved endurance, increased stroke volume and cardiac output. • Muscular capacity refers to the spectrum of muscular capability. This includes muscular endurance (i.e., the ability to apply force over a long period of time or to complete repeated m