The primary purposes of the cardiovascular and respiratory systems are to deliver adequate amounts of oxygen and remove waste from working muscles. During exercise, the reason for cardiovascular regulation is to maintain adequate blood flow in order to carry oxygen to working muscles. In addition, the circulatory system transports nutrients, e.g. glucose, and aids in temperature regulation. During exercise, the demand for oxygen to the muscles is 15 to 25 times greater than at rest. The heart cannot accomplish this by itself, and does not work in isolation. The respiratory system and cardiovascular system function together as a ‘coupled unit’, delivering the body’s oxygen and nutrients and taking away carbon dioxide and other waste to maintain homeostasis.

Exercise over a sustained period of time usually more than 8 weeks will bring about some long term adaptations to the body. These adaptations will be determined by the intensity, duration and frequency of the activities in the programme. The physiological changes will impact upon the musculo-skeletal, cardio – vascular/respiratory and the energy systems

Exercise physiology is underpinned by the energy systems. When we exercise our body is constantly working to supply muscles with enough energy to keep going. The way energy is made available to muscles changes depending on the specific intensity and duration of exercise