RESPIRATORY RESPONSE TO EXERCISES

Effects of maximal exercises:

• A 25-fold increased oxygen consumption & carbon dioxide production.

• Alveolar & arterial PO₂ & PCO₂ maintained equal at rest & during exercise by,

– Increased pulmonary ventilation.

– Increased pulmonary perfusion.

• Due to increased cardiac output. 

– Increased pulmonary diffusion.

• Due to increased perfusion

Pulmonary ventilation:

At onset of exercise:

• Increases abruptly → Brief pause → Gradually increase.

• Abrupt increase due to,

– Psychic stimuli.

– Afferent impulses from proprioceptors in muscles, tendons, & joints.

During moderate exercise:

• Increased due to increased respiratory depth.

• Arterial pH, PCO, & PO, remain constant.

During strenuous exercise:

• Increased respiratory rate. 

• Increased body temperature→ Increased heat production

– Result of increased oxygen utilization.

• Increased plasma K+ (Hyperkalemia) 

– Stimulates peripheral chemoreceptors.

– K+ released from skeletal muscle.

• Increased neuronal sensitivity to CO.

• In severe & sustained exercise, lactic acidosis occurs.

– Ie., Lactic acid accumulation in blood & pH drops as low as 7.2.

– Acidosis further increases pulmonary ventilation out of proportion to O₂ consumption.

– During this period arterial PCO₂ may drop significantly.

• Oxygen-hemoglobindissociation curve is shifted to right.

– Due to Local PCO_2.

– Temperature.

– Increased H+ concentration.

• Increased O₂ extraction by tissues.

• Exercise increases endogenous opioids release.

– Associated with mood enhancement.

• Exercise is also stressful.

– Increases stress hormone levels,

• GH.
• Glucagon
• ACTH.
• Cortisol.
• Catecholamines.

– Decreased insulin level.

• Lactic acid accumulation causes muscle soreness.