Exercise Cardiac Output — FRCA Primary MCQ

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ModeratePhysiology - CardiovascularExercise Cardiac OutputFRCA Primary

During exercise cardiac output may increase from 5 L/min to 25 L/min. Which mechanism contributes most to this increase?

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Correct answer: A — Increased heart rate with increased stroke volume via increased contractility and preload

Exercise increases CO via: increased HR (sympathetic stimulation / reduced vagal tone up to ~200 bpm) and increased SV (increased preload from muscle pump and venoconstriction / increased contractility from sympathetic stimulation / decreased afterload from skeletal muscle vasodilation). Both HR and SV contribute but HR is the greater contributor at maximal exercise.

Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist