• Question: What happens to my heart when I excercise?

    Asked by Juan pi to Andrew, Dan, Emilia, Helen, Katy, LauraAnne, Stephanie on 12 Nov 2016.
    • Photo: Dan Gordon

      Dan Gordon answered on 12 Nov 2016:

      The heart is a muscle and its role is to push blood around the circulatory system. Within the heart their are four chambers, two atria which are receiving chambers for incoming blood and two ventricles which are chambers for ejecting blood. As blood enters an atria the pressure starts to rise, this triggers the opening of the valve between the atria and the connected ventricle. The blood now rushes into the ventricle. As this happens the pressure rises until the pressure exceeds that in the atria which is now falling. At this point the valve closes and we get what is termed an isovolumetric contraction. This triggers the opening of the 2nd valve and the muscle of heart contracts, under stimulation from the nervous system. Now the pressure in the ventricle is higher tan in the connecting artery causing the blood to rush from the ventricle. As the pressure falls there will be a point when it is higher in the artery than the ventricle and the vale closes.
      SO when you exercise the heart rate goes up but so to does the stroke volume. This is ten volume of blood per beat of the heart. However we have come to realise that despite an increase in heart rate with exercise intensity that stroke volume doe snot keep rising. This reaches a peak at around 50% of maximal output. SO the way the blood flow and oxygen delivery to the muscles are increased is through the hart rate.

    • Photo: LauraAnne Furlong

      LauraAnne Furlong answered on 12 Nov 2016:

      An interesting thing to add is that when we start exercising, the place in the body that the most blood gets sent to changes, this is called the vascular shunt mechanism. This is where the working muscles get priority so the majority of the blood flow goes to them – the blood flow to other organs like the kidneys or your digestive system (that don’t really need it at that time) gets reduced, to ensure the most oxygen gets sent where it is needed most-at the working muscle. This effect is most obvious when you are exercising.

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