The Exercise and Blood Pressure Connection
Hypertension, or high blood pressure, is something that affects huge numbers of people. In the USA & UK around 20% of the population has hypertension – and around a quarter of those don’t know they have it!
High blood pressure doesn’t give any warning signs and for this reason, it is known as the ‘silent killer’. Because there are often no symptoms, the only sure way you can know if you have hypertension is by having your blood pressure checked. Many people think they will feel dizzy, have headaches, suffer cramp in the legs, have a puffy face or red nose or just feel irritable when they have high blood pressure. Unfortunately, unless it is extremely high, none of these things happens – and many thousands of us are walking around with high blood pressure feeling fit and healthy. Very sadly, a stroke or heart attack is the first thing they know about it.
Blood pressure (BP) is complicated to put it mildly and trying to work what can make it go wrong still puzzles medical scientists. Think of a central heating system. Water is pumped through pipes to radiators all over the house. In the human body, the pump is your heart, the pipes are your arteries and veins, the radiators are your liver, kidneys, intestines, brain, skeleton, hands and feet. The central heating pump has to work hard to push water around the house. Likewise your heart has to work hard to push blood around your body. The amount of “push” the heart has to give with every beat is your blood pressure.
Just as the water pump has to work harder if your pipes and radiators get furred up, so it is with your heart if there is resistance to blood flowing through your arteries, veins and organs. This results in an increase in your BP and might be caused by stress, smoking, being overweight, drinking too much alcohol, eating too much salt and lack of exercise. Family history and taking the contraceptive pill are also factors known to be associated with elevated blood pressure.
The UK Coronary Prevention Group suggests that every adult over 25 years should have BP checked at least once every 5 years. Generally, women have their BP checked more often than this during routine visits to the doctor. However, far fewer men have regular BP checks.
The instrument used to check blood pressure is just an inflatable cuff with a gauge attached to it. The cuff is wrapped around your upper arm and pumped up in order to stop the flow of blood into your lower arm. The pressure cuff is slowly released and doctor or nurse will listen through a stethoscope, placed on your brachial artery near your elbow, for the sound of blood flow returning. When the first sound is heard this is the highest pressure (called ‘systolic’ BP) and is normally around 110-140mmsHg (the units are ‘millimetres of mercury’). This then is the pressure of blood being pumped by the heart into your arteries. The last point where the sound is heard is the lowest pressure (called ‘diastolic’ BP) and is normally around 60-90mmsHg. This gives a good indication of the elasticity of your arteries and the resistance to blood flow.
So, if you have a BP of 120/80, the 120 is the highest pressure, when the heart contracts and the 80 is the lowest pressure between the heartbeats.
If your BP is below 140/90 this is usually considered normal. If it is over 160/100 this is generally considered too high and may need medical treatment. However, there is really no hard and fast rule because there is no definite point between high and low. Your doctor must decide what is best for you. For example, many doctors wouldn’t treat a BP of 160/100 in a 75-year old, but likely would for a 35-year old.
Sometimes, blood pressure can be too low (less than 100/60). This is termed hypotension. Low BP is often accompanied by dizziness, lightheadedness or proneness to fainting when moving from lying or sitting to a standing position, particularly in a hot environment (e.g. sauna) or when emerging from a swimming pool. Whilst it is more common in elderly individuals low BP can occur in younger people. Both high and low blood pressure should always be checked out with your GP who will interpret the readings for any clinical significance.
The Exercise and Blood Pressure Connection
A brisk walk, cycle or swim will cause your systolic BP to rise from a resting level of around 120 to 150 or even 200. The harder you exercise, the higher it goes. Interestingly your diastolic BP remains roughly the same at rest as in exercise (around 80-90). But after exercise blood pressure falls – often below normal levels – and this effect can last up to several hours. Over time, regular exercise will help ‘loosen up’ your blood vessels thereby lowering your resting BP – rather like widening a water pipe lowers water pressure. This is one reason why you feel relaxed after physical activity.
Resistance training doesn’t appear to be as effective as aerobic training in helping control blood pressure – and moderate aerobic exercise appears better than higher-intensity strenuous exercise. Many studies have shown that regular moderate exercise can help both prevent high blood pressure and help to cure it. In people with hypertension, research shows that moderate aerobic exercise can have a highly beneficial effect – and this can take place within the first few weeks. However, those with severe hypertension should first consult with their doctor before embarking on an exercise programme.
Also, when a person stops taking exercise, BP will return to its initial level. In other words, the BP-lowering effect of exercise depends on a regular (3 to 5 times a week) schedule of moderate physical activities.
So, to help keep your blood pressure normal, watch your weight, cut down on alcohol and salt – and keep active!