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Posts Tagged ‘blood volume’

Heart and circulation

  • When you are pregnant sudden demands are placed on your body’s heart and circulatory system – a growing baby and your increased body weight, and now you are exercising – that’s another demand.
  • Slowly the volume of blood circulating in your body increases, so much so that by the end of your pregnancy you may have 40 % more circulating blood.
  • Although there is an increase in red blood cells to carry more oxygen round the body, hormones from the heart and adrenal glad cause the body to hold onto more salt and water.
  • This leads to an increase blood volume (but from blood plasma rather than red blood cell mass).  At times this can increase feelings of fatigue during the day, and play a part in pregnancy anaemia, known as physiological anaemia.

Heart Rate

  • To accommodate the extra demands your overall blood volume will increase.  Your heart chambers expand, the amount of blood your heart pumps during each beat increases (by up to 15 bpm).  This means that your resting heart rate will be increased and exercise will elevate your heart rate quicker (even if you were pretty fit before pregnancy).
  • Because of this duration and intensity of any exercise class needs to be modified, so to the warm up and cooldown.

Respiration 

  • We cannot live without breathing (in fact Pilates said “Above all, learn how to breathe correctly”).
  • The air we breathe ultimately makes its way to baby, via the placenta  and umbilical cord.
  • Carbon dioxide sensitivity is increase by the hormone progesterone (see here for more details) which makes simple tasks like walking up and down stairs more breathless.
  • It means you are working harder and responding to changes in your respiratory system – not that your are not fit.
  • During the end of your pregnancy there is a demand for up to 20% more oxygen than pre-pregnancy; combine this with the increased carbon dioxide sensitivity your breathing will become faster and you are more likely to become breathless as the body tries to expel the increased levels of carbon dioxide.
  • As baby grows the diaphragmatic movement becomes restricted, which means the diaphragm cannot move as freely as it once did, and reduces your ability to inhale a full breath.  This too can make you feel breathless.
  • Hormones accommodate this by allowing the ribcage to flair outward, thereby allowing the same volume of air into the lungs, but by another mechanism.
  • This flaring can cause some pain or discomfort around the ribs or mid back.  However, once baby’s head is ‘engaged’ this usually goes and your might feel a huge release – allowing you to breathe better!
  • Breathe at your own rate and tempo – don’t work too hard – make sure you can hold a conversation whilst exercising.
  • Don’t breathe too deeply or rapidly as this may cause you to hyperventilate – you will know as you will feel very dizzy , clammy and look pale.  If this happens, cup your hands over your mouth and nose and breathe normally until you recover.

Initial vascular under-fill

  • In the very early stages of pregnancy hormones initiate reduced response and relaxation in blood vessels and muscle cells.
  • This means that the heart, arteries and veins increase their elasticity and volume almost immediately.
  • The effect of these changes means that for a short rime there is not enough blood to circulate; blood pressure will fall – (called vascular under under-fill).
  • You may feel light-headed if you stand still for a long while or on standing if you have been seated for a while.
  • It would be sensible to avoid either of these positions, and also consideration needs to be given when getting up/down from the floor.
  • Seated or all-four positions may be more comfortable and reduce the effects of low blood pressure.
  • If you feel unwell you must consult your health care professionals.
  • Symptoms often disappear by week 20, but some may persist during the pregnancy.
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