7th February 2024

Exercise physiology and exercise testing

Cardiovascular changes during exercise

During exercise, there is a marked increase in muscle metabolic rate, resulting in increased oxygen demand and the need for an increased rate of CO2 and metabolite clearance. Hence, our cardiovascular system needs to be able to mount a physiological response to meet these demands.

The cardiovascular system undergoes various physiological changes during exercise, and these include:

• Significant increase in cardiac output. At rest, cardiac output for an average individual is around 5L/min. During exercise, this can be increased up to 25L/min to meet the metabolic demand of exercising muscles. The sympathetic system mediates this increase in cardiac output.
• Stimulation of the sympathetic system increases heart rate and increase in myocardial contractility.
• Skeletal muscle activity results in vasoconstriction, increasing venous return, hence increasing preload. An increase in preload contributes to increased cardiac output.
• Skeletal muscle activity also produces metabolites that cause vasodilation, resulting in decreased systemic vascular resistance.

Other changes that occur during exercise include changes to regional blood flow. The most significant increase in blood flow is to the skeletal muscles. Blood flow to other organs is also affected during exercise. Changes include:

• Increase in coronary blood flow
• Increase in blood flow to the skin to aid heat dissipation
• Decrease in splanchnic blood flow
• Decrease in renal blood flow but to a lesser degree than splanchnic blood flow.
• Cerebral blood flow is maintained.

References

Patel, P. N., & Zwibel, H. (2023). Physiology, Exercise. In StatPearls. StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK482280/