Cardiac output

[lala1911]

Why is cardiac output unchanged at rest and submaximal activity?
Is it because of the decreased heart rate and the increase in SV?

[Dantini]

Hey lala, I assume you are referring to the Chronic adaptation of increased left ventricle size (Cardiac Hypertrophy) due to aerobic exercise. This adaptation increases the stroke volume due to increased contractility of the left ventricleand given that the body generally requires the same amount of oxygen at rest whether you are trained or untrained. Given the equation from units 1+2 Physical Education, Cardiac output (Q) = Stroke volume (SV) x Heart Rate (HR), an increased SV would allow HR to decrease to give the same Q. This benefits performance as there is more room for Heart Rate to increase from resting levels, allowing for a greater capacity to transport oxygen through the blood at higher intensities, allowing the body to more effectively oxidize metabolic byproducts.
I hope this answers your question.