What is Blood pressure?

Blood pressure can be defined as the measure of the force that is applied to the walls of the arteries as the blood runs though them. We measure blood pressure in millilitres of mercury (mmHg). A blood pressure reading has two numbers. The first number represents the systolic blood pressure (BP when the heart is contracting) and the second number represents the diastolic blood pressure (BP when the heart is relaxing).

Blood pressure classifications

Optimal blood pressure 120/80 mmHg or lower. A reading such as this can suggest a low risk of cardiovascular disease. If blood pressure increases until there is a reading of 140/90 mmHg a doctor can classify this as stage hypertension which can suggest the onset of cardiovascular disease. A blood pressure reading of 180/110 mmHg would represent stage 3 hypertension which is considered an absolute contraindication to exercise. Hypotension is the term used to describe low blood pressure such as 100/60mmHg although this is not considered to increase the risk of cardiovascular disease.

Classification Systolic (mmHg) Diastolic (mmHg)
Low <100 <60
Optimal <120 <80
Normal <130 <85
High normal/Pre-hypertension 130-139 85-89
Stage 1 hypertension 140-159 90-99
Stage 2 hypertension 160-179 100-109
Stage 3 hypertension >180 >110

Cardiac output

The volume of blood pumped out of the heart in one minute is called cardiac output. The higher the cardiac output the higher the blood pressure. When we exercise our cardiac output increases which intern increases our blood pressure. However, this is just a short term effect as regular aerobic exercise overtime can reduced resting blood pressure.

Total peripheral resistance

The resistance the blood vessels offer to blood flow is called total peripheral resistance. The greater the total peripheral resistance the greater the blood pressure.

Blood pressure = cardiac output x total peripheral resistance

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