Exercise is the performance of physical exertion for improvement of health or for the correction of physical deformity.

Voluntary muscular movement or exercise is a cortical phenomenon and is under the "feed back" control of cerebellum. During muscular exercise, the energy needs of the muscle are increased tremendously and these energies are met with increased metabolism, and these requirements are met with by causing oxygen rich RBC more available to the active sites. This happens by increasing heart rate, cardiac output, increasing venous return, increasing vascular resistance in the inactive muscle, redistribution of blood and increasing pulmonary ventilation.

Exercise is defined as intentional increased muscular activities, planned, structured and basically repetitive contraction and relaxation of groups of muscles. Exercise is a purposeful increased physical activity with great health benefits. Health benefits include prevention of certain diseases, promotion of physical fitness and improvement in the performance in the sports field. The study of exercise physiology deals with the physiochemical processes of various body systems. their adaptation in handling increased conversion of chemical energy to mechanical work.

Classification of exercise

Types of exercise are two - Isotonic and Isometric.

Exercise demands a great amount of energy. The metabolic rate increases during exercise, chemical energy is converted to mechanical work. The major sources of energy are 1. ATP 2. Phosphocreatinine 3. Fatty acids 4. Glucose and glycogen 5. Lactic acid. The immediate source of energy for muscular activities is derived by the breakdown of ATP and regeneration of ATP by phosphocreatinine. During aerobic exercise sufficient oxygen is made available. During this period ATP is regenerated by the oxidation of glucose, fatty acids and ketone bodies.

During anaerobic conditions glycolysis and phsphocreatinine can generate ATP to some extent. During the prolonged exercise stored energy is derived from triglycerides and tree fatty acids. Greater availability of fatty acids also made by the actions of growth hormone and catecholamines.large amount of fatty acids are available for breakdown, it decreases the demand on breakdown of muscle glycogen and glucose for energy. During anerobic exercise glucose breakdown produce lactate. From the muscles lactate is collected and carried to liver by the blood. In the liver lactate is converted to glucose by gluconeogenesis. This forms the Cori's cycle. Later glucose is released from liver to be carried to the muscles. 

Physiological changes during exercise. Exercise generates a great metabolic stress on the body. It is faced by adaptations by different organs and systems.