How do our bodies work during sport?

To stay alive, every one of our cells needs oxygen and glucose for respiration. The glucose and oxygen are used by mitochondria in our cells to produce energy, carbon dioxide and water.

The cells get the oxygen and the glucose from the bloodstream and get rid of carbon dioxide and water to the bloodstream. Oxygen comes from breathing and this is also how carbon dioxide is got rid of. Glucose comes from the products of digestion. Water is eliminated from the body through sweat, breathing and urine.

The Heart and Circulation

The heart works like a double pump.

• The journey starts in the right atrium.
• The blood is pumped by a contraction of the right atrium and moves into the right ventricle.
• The right ventricle contracts.
• This pushes the blood into the pulmonary artery.
• The pulmonary artery carries the blood to the lungs.
• The artery splits up into lots of tiny capillaries that go all the way through the lungs.
• The red blood cells pick up oxygen from the lungs.
• The lung capillaries join up and form the pulmonary vein.
• This goes back to the heart.
• The pulmonary vein empties into the left atrium.
• The left atrium contracts and pushes blood down and into the left ventricle.
• The left ventricle contracts and pushes blood into the aorta, the main artery to the body.
• The aorta splits up and carries blood all over the body through a network of smaller arteries, which end in capillaries.
• Some of the blood arrives at the gut where it picks up glucose.
• The oxygen and glucose are delivered to the cells.
• The capillaries join up and form into the vena cava, the main vein from the body.
• The vena cava empties into the right atrium.

During exercise, cells need to do more work. This means they need to have more energy. They get their energy from respiration, which they need more oxygen and glucose for. The blood supply to all cells therefore needs to be increased. To do this, the pituitary gland in the brain releases adrenaline, which increases the rate at which the heart beats. After exercise, the heart rate recovers as the oxygen/glucose demand decreases to normal. This normally takes a few minutes, and will be less in a fitter person.