Effects Of Exercise On Respiration

Effects Of Exercise On Respiration Introduction

• Muscular exercise brings about a lot of changes in various systems of the body.
• The degree of change depends upon the severity of exercise.

Effects Of Exercise On Respiration

1. Pulmonary Ventilation:

• Pulmonary ventilation is the amount of air that enters and leaves the lungs in one minute.
• It is the product of tidal volume and respiratory rate. It is about 6 liters/ minute with a normal tidal volume of 500 mL and a respiratory rate of 12/minute.

Read And Learn More: Medical Physiology Notes

• During exercise, hyperventilation, which includes an increase in the rate and force of respiration occurs.
• In moderate exercise, the respiratory rate increases to about 30/minute, and tidal volume increases to about 2000 mL.
• Thus, pulmonary ventilation increases to about 60 liters/minute during moderate exercise. In severe muscular exercise, it rises still further up to 100 liters/ minute.

Various factors are involved in increasing pulmonary ventilation during exercise:

1. Higher centers
2. Chemoreceptors
3. Proprioceptors
4. Body temperature
5. Acidosis

1. Higher Centers:

• The rate and depth of respiration increase during the onset of exercise.
• Sometimes, before starting the exercise, the thought or anticipation of exercise itself increases the rate and force of respiration.
• It is a psychic phenomenon due to the activation of higher centers like the Sylvian cortex and motor cortex of brain.
• The higher centers in turn accelerate the respiratory processes by stimulating respiratory centers.

2. Chemoreceptors:

• The chemoreceptors, which are stimulated by exercise-induced hypoxia and hypercapnia, send impulses to the respiratory centers.
• The respiratory centers in turn increase the rate and force of respiration. The chemo-receptors are described in detail.

3. Proprioceptors:

• Proprioceptors, which are activated during exercise, send impulses to the cerebral cortex through the somatic afferent nerves.
• The cerebral cortex in turn causes hyperventilation by sending impulses to the medullary respiratory centers.

4. Body Temperature: Body temperature, which increases by muscular activity, increases ventilation by stimulating the respiratory centers.

5. Acidosis: Acidosis developed during exercise also stimulates the respiratory centers resulting in hyperventilation.

2. Diffusing Capacity For Oxygen:

• During exercise, blood flow through the pulmonary capillaries is increased.
• Because of this, the diffusing capacity of alveoli for oxygen is increased.
• The diffusing capacity for oxygen is about 21 mL/minute at resting conditions.
• It rises to 45-50 mL/minute during moderate exercise.

3. Consumption Of Oxygen:

• The oxygen consumed by the tissues, particularly the skeletal muscles is greatly enhanced during exercise.
• Because of vasodilatation in muscles during exercise, more amount of blood flows through the muscles.
• So, more amount of oxygen diffuses into the muscles from blood.
• And, the amount of oxygen utilized by the muscles is directly proportional to the amount of oxygen available.

4. Oxygen Debt:

Oxygen debt is the extra amount oxygen required by the muscles during recovery from severe muscular exercise.

• After a period of severe muscular exercise,
  the amount of oxygen consumed is greatly increased.
• The oxygen required is more than the quantity available to the muscle.
• This much oxygen is required not only for the activity of the muscle but also for the reversal of some metabolic processes such as:
• Reformation of glucose from lactic acid accumulated during exercise
• Resynthesis of ATP and creatine phosphate
• Restoration of the amount of oxygen dissociated from hemoglobin and myoglobin.
• Thus, for the above reversal phenomena, an extra amount of oxygen must be made available in the body after severe muscular exercise.
• The oxygen debt is about six times more than the amount of oxygen consumed under resting conditions.

5. V_O2 Max:

• V_O2 Max is the amount of oxygen consumed under maximal aerobic metabolism.
• It is the product of maximal cardiac output and the maximal amount of oxygen consumed by the muscle.
• In a normal active and healthy male, the V02 Max is 35-40 mL/kg body weight/minute.
• In females, it is 30-35 mL/kg/minute.
• There is an increase of V_O2 Max by 50% during exercise.

6. Respiratory Quotient:

• The respiratory quotient is the molar ratio of carbon dioxide production to oxygen consumption.
• The respiratory quotient in resting condition is 1.0 and during exercise, it increases to 1.5-2.
• However, at the end of the exercise, the respiratory quotient reduces to 0.5.