Fitness and respiration
Blood is under pressure in the arteries so that it can reach all parts of the body. Respiration releases energy for cells from glucose. This can be aerobic respiration, which needs oxygen, or anaerobic respiration, which does not. During exercise, the breathing rate and heart rate increase. During hard exercise an oxygen debt may build up.
Arteries carry blood away from the heart.
The blood in the arteries is under pressure because of the contractions of the heart muscles. This allows the blood to reach all parts of the body. You can see how the heart pumps the blood to the lungs and rest of the body by studying this animation:
Blood pressure is measured in millimetres of mercury, mmHg. There are two measurements:
A young, fit person may have a blood pressure of about 120 over 70, which means their systolic pressure is 120 mmHg, and their diastolic pressure 70 mmHg.
Blood pressure varies with age. It also varies with lifestyle factors such as: