Exercise can control your blood pressure

It is a well-known fact that exercise is good for physical and mental well-being. Exercise is considered a ‘medicine’ (Exercise is Medicine Australia, 2014), and is highly recommended for the management of hypertension (high blood pressure) (Weber et al., 2014; Whelton et al., 2018; Williams et al., 2018).

However, you may wonder how exercise helps in optimizing blood pressure? How performing regular exercise or physical activity can reduce high blood pressure? Answering these questions is the focus of this blog post, so stay with me!

What is blood pressure?

Blood pressure is the pressure exerted on the walls of the blood vessels by the pumping effect of the heart. To give you an overview: the heart has four chambers, named atriums (left and right) and ventricles (left and right). The big tubes through which blood is transported to, and away from, the heart are called the pulmonary artery and aorta. The smaller tubes which distribute blood from aorta are called arteries.

The left ventricle’s contraction pumps blood into aorta and arteries, and that force exerts pressure on the walls of the arteries. This is recorded as two figures called ‘systolic’ and ‘diastolic’ pressure. The first figure (systolic) is the pressure developed by contraction of the left ventricle, and the second (diastolic) is the pressure that remained after the relaxation of the left ventricle.

The normal values for blood pressure are below 120 mmHg and 80 mmHg for ‘systolic’ and ‘diastolic’ respectively [mmHg: Mercury millimeters, the units of blood pressure] (Whelton et al., 2018; Williams et al., 2018).

Different ranges of blood pressure are categorized into normal, elevated, and high blood pressure by the American College of Cardiology Guideline and other guidelines (Whelton et al., 2018). You can see blood pressure values for each category in the table below (Table 1).

Category	Value [mmHg]	Status
Normal	below 120/80	Normal blood pressure Exercise is beneficial to keep this level or to lower it Very low heart disease risk
Elevated	120 – 129/80	Elevated or above-normal blood pressure Need exercise to lower High risk of high blood pressure or heart disease or stroke in future
Stage I	above 130/80	High blood pressure Need lifestyle modifications ± medications Heart disease risk is moderately high
Stage II	above 140/90	High blood pressure: Need medication + lifestyle modifications, Heart disease risk is high

Mathematical expression for blood pressure

There are approximately 5 liters of blood in a human body. This volume of blood is constantly being pumped around by heart. The amount pumped over one minute is called cardiac output (CO). The wall of the left ventricle contracts and pushes the blood to the main artery which distributes around the body through the arterial system.

The volume of blood pumped out by one stroke is known as stroke volume. (Hall J.E., 2016). The heart makes 72 strokes or ‘beats’ per minute which is called heart rate. Therefore, the product of Stroke volume (SV) and Heart rate (HR) is the volume of blood pumped out of the heart per minute. This is called Cardiac Output (CO). Cardiac output can be mathematically expressed as the product of HR and SV (CO = HR * SV) (Hall J.E., 2016).

Let’s go back to physics for a minute. When a fluid is moving through a tube there is a resistance to the flow posed by the walls of the tube. If the inner surface of the tube is smooth and the lumen (or diameter), is large, it is easy to move the fluid through the tube.

You might have had an experience of drinking something using a straw with a larger diameter, it is easier than drinking through a straw with a smaller diameter. Thus, the resistance to a flow of a fluid is based on the diameter and thereby the cross-sectional area of the tube and the texture of the inner surface of the tube. If the diameter of a tube is the large and the inner surface of the tube is smooth, the resistance to move the fluid through the tube is low.

This physical principle can be applied to the blood flow also through the arteries because arteries are tubes and blood is a fluid! In accordance, the resistant to blood flow by the arteries in the body is called Peripheral Resistance (PR).

The above two paragraphs described what the Cardiac Output and the Peripheral Resistance is. So, the Blood Pressure (BP) can be expressed as the product of Cardiac Output and the Peripheral Resistance. (Hall J.E., 2016)

How does exercise can reduce blood pressure?

When someone does exercises, the body, especially the muscles, needs more blood. To supply more blood to muscles, heart increases its rate which means that the left ventricle contracts harder to pump more blood out of the heart. Thus, cardiac output increases and subsequently blood pressure increases, at the time of the exercise.

Following the same equation again:

Being subjected to rapid and strong contractions, the muscles of the ventricles become more elastic and stronger (Exercise is Medicine Australia Factsheet Full version, 2014). This results in more volume (more room) in the left ventricle to maintain the Cardiac Output in a smaller number of strokes (in a lower Heart Rate).

As a result, the volume of blood needed to be transported around the body can be turned over by a smaller number of beats per minute. This will lead to reduced blood pressure.

At the same time, during exercising the water in the body is removed as sweat which leads to a reduction of the total blood volume (Pescatello et al., 2004). It will reduce the excess work that the heart needs to do to pump the excess blood out as the blood volume decrease.

Additionally, exercise increases the contraction of the left ventricle and thereby the pressure on the walls of the arteries caused by the strong and rhythmical pumping. This helps to increase the elasticity of the walls of the arteries (Pescatello et al., 2004). The increased elasticity and the bigger lumen (diameter) of the arteries reduce Peripheral Resistance.

Thus, the heart will not need to pump blood that hard because of the less resistance to the blood flow in the arteries.

How much exercise is enough?

Though the blood pressure increases during the exercises, it falls below the normal level after the exercise (Cao et al., 2019). This blood pressure-lowering effect stays up to 24 hours and if the exercise is done at regular intervals, daily or once in two days, the lower or normal level of blood pressure can be maintained.

The recent recommendations of the duration of exercise is 150 – 300 minutes per week in regular intervals (ACSM, 2019). Not 150 min in one day or two. Therefore 30 – 60 minutes of exercise in five days of the week would be more beneficial than two hours of exercise on the weekend (ACSM, 2019).

Which exercise should be done?

For overall health, any activity that raises heart rate and makes you breathe harder is great, for example, aerobics (Ministry of Health New Zaland, 2015). Cycling, jogging, walking, running, swimming are all options for aerobic exercise. Roughly, walking 3-4 km, jogging 2 km, cycling 6-8 km will be able to be covered in the time range of 30-60 minutes is where you can start.

Further, lifting weights generally called strength training is also beneficial and is advised at least twice a week (ACSM, 2019; Ministry of Health New Zaland, 2015). Strength training is not only going to the gym but also simply doing push-ups carrying shopping or walking up the hill. Strength training becomes crucial especially for the elderly.

The most important aspect, however, is to do exercise within your limits: start slow and progress as you get better at it.

In summary, the exercise will reduce Heart Rate, Stroke volume, and thereby Cardiac Output and the Peripheral Resistance, all of which positively influence Blood Pressure. Thus, exercise can be used as a therapy to treat blood pressure and to prevent developing it.

Stay active!

Academic readings

ACSM. (2019). ACSM Physical Activity Guideline Executive Summary.

Cao, L., Li, X., Yan, P., Wang, X., Li, M., Li, R., . . . Yang, K. (2019). The effectiveness of aerobic exercise for hypertensive population: A systematic review and meta-analysis. Journal of Clinical Hypertension. doi: 10.1111/jch.13583

Exercise is Medicine Australia Factsheet Full version. (2014). Hypertension and Exercise.

Exercise is Medicine Australia, H. f. s. (2014). Hypertension and exercise Australia: Exercise is Medicine Australia.

Hall J.E. (2016). Pocket companion to Guyton and Hall textbook of medical physiology,   Retrieved from http://www.otago.ac.nz.ezproxy.otago.ac.nz/library/primo/

Ministry of Health New Zaland. (2015). Eating and activity guidelines for New Zealand adults. HP6271,Ministry of Health,PO Box 5013,Welington 6154, NZ,.

Pescatello, L. S., Franklin, B. A., Fagard, R., Farquhar, W. B., Kelley, G. A., & Ray, C. A. (2004). Exercise and Hypertension. Medicine & Science in Sports & Exercise, 36(3), 533-553. doi: 10.1249/01.mss.0000115224.88514.3a

Weber, M. A., Schiffrin, E. L., White, W. B., Mann, S., Lindholm, L. H., Kenerson, J. G., . . . Harrap, S. B. (2014). Clinical practice guidelines for the management of hypertension in the community a statement by the American Society of Hypertension and the International Society of Hypertension. Journal of Hypertension, 32(1), 3-15. doi: 10.1097/HJH.0000000000000065

Whelton, P. K., Carey, R. M., Aronow, W. S., Casey, D. E., Jr.,, Collins, K. J., Dennison Himmelfarb, C., . . . Wright, J. T., Jr.,. (2018). 2017ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines,. Journal of American College of Cardiology,, 71(19), 2199-2269. doi: 10.1016/j.jacc.2017.11.005

Williams, B., Mancia, G., Spiering, W., Agabiti Rosei, E., Azizi, M., Burnier, M., . . . Group, E. S. C. S. D. (2018). 2018 ESC/ESH Guidelines for the management of arterial hypertension. European Heart Journal,, 39(33), 3021-3104. doi: 10.1093/eurheartj/ehy339