ABSTRACT
People participate in physical exercise to improve general health, to improve performance-related fitness for a particular sport, and/or for recreation and relaxation. Improved fitness results from adaptation and improvement of cardiovascular, respiratory, and metabolic function as well as local responses in the muscle groups engaged. The nature and magnitude of any training effect are influenced by the frequency, duration, and intensity of exercise. The process of determining and controlling appropriate exercise intensity presents a challenge, which has implications related to both physiological changes and to individual compliance within an exercise programme.
