by muscular activity. The second phase of gradual increase in the ventilation occurs due to an increase in the temperature, and chemical changes in the arterial blood produced by muscular activity. Pulmonary diffusing capacity: The rate of diffusion of gas between the alveoli of the lungs and the blood of the lung capillaries is called pulmonary diffusing capacity. During exercise the pulmonary diffusing capacity for oxygen increases.
Hyperventilation: An increased breathing due to an increased tidal volume or increasing respiratory rate or both is referred to as hyperventilation. Total lung capacity: The volume of air in the lungs at the end of maximal inspiration is termed as total lung capacity. During exercise the total lung capacity slightly decreases. Vital capacity: The maximal volume of air which is forcefully expired after maximal inspiration is called vital capacity.
Effects of Exercise on Muscular System Muscle is a tissue which has the power of contraction. Skeletal muscles are the main muscles for physical activities and exercises. Several changes take place in the skeletal muscles depending upon the type of training which an individual is undergoing. The effects of exercise on muscular system are summarised as follows.
Muscular hypertrophy: Due to regular exercise, training muscles become enlarged. Muscle fibers, diameter and length increases. The total amount of protein, glycogen and enzymes are increased. Aerobic changes: By training, the amount of myoglobin increases which helps for better supply of O to the working muscles of the body.
By training, muscles produce energy by increased oxidation of glycogen. A trained muscle uses more fat to supply more energy. Anaerobic changes: These are the changes which help in supply of energy in the absence of O . •• Increased lactic acid tolerance •• Change in blood flow of the muscles •• Change in red and white fibres of the muscles Training and capillary supply: Endurance training increases the capillary ratio (expressed as capillaries per fiber).
Training increases capillary density as well. Influence on performance: As muscles become stronger, they contract with less exertion during a maximum voluntary force. A greater perfusion occurs, and the