The mechanism of inspiration and expiration is known as respiration. It is controlled by medulla oblongata of the brain. It helps in adequate supply of O2 and elimination of CO2 from the body.
The effects of exercise on respiratory system are summarised as follows:
Tidal volume: It is referred to as the volume of air inspired or expired per breath. During rest, it is around 500 ml; during exercise it increases; during maximal exercise, it increases 5 to 6 times above the resting values.
Respiratory rate (F): It is also known as breathing rate or breathing frequency. It is defined as the number of breaths per minute. At rest, it is 12–20 per minute, during exercise it increases to 2–3 times.
Minute ventilation or Pulmonary ventilation (PV): It is commonly referred to as the breathing process of lungs during inhalation and exhalation.
PV = Tidal volume × Respiratory rate
PV = (TV × RR)
During rest = 8 litres/minute
(PV changes with body size, it is smaller in female and larger in male.)
During exercise: PV increases during exercising. The initial rise in the ventilation is due to the increased stimulation of the inspiratory centres caused 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.
