High Blood Pressure Pt 2
The medical ill effects of raised BP
Persistently raised blood pressure damages the walls of the arteries and this predisposes the person to atheroma, or hardening of the arteries (see below). This is a narrowing of the blood vessels by patchy plaques, which build up over many years, reducing the internal dimensions – or lumen – of the vessels and sometimes leading to complete blockage. The most damaging results include heart attacks, strokes and, less commonly, gangrene of the legs. Other ill effects of hypertension include kidney failure, heart failure and vascular dementia. Hypertension is the largest of all the risk factors for stroke, responsible for about 54 per cent of cases. It is also an important risk factor for heart attacks, being implicated in about 47 per cent of cases.
Exercise in the prevention of raised blood pressure
Physical activity has a direct effect on blood pressure. A large Harvard alumni study showed that those who engaged in regular vigorous leisure activities had a 33 per cent lower risk of developing hypertension than those who took little exercise.
There is a dose-response relationship between physical fitness and BP – that is to say, the fitter you are, the lower your BP is likely to be. In a study of 5,249 middle-aged males in Copenhagen, every increase in VO2max of 10ml/min/kg (see glossary and previous blogs) was associated with a 2mmHg reduction in both systolic and diastolic BP.
A study that examined exactly which form of sport or exercise was most effective found that running, tennis, team sports, exercise classes and resistance training were best for keeping BP low. More specifically, regular muscle-strengthening lowers the risk of developing hypertension by about 60 per cent.
Exercise in the treatment of raised blood pressure
Whatever your BP may be, you would probably be better off if, by your own efforts, you could bring it down. There are many aspects of lifestyle that contribute to pushing up your BP. The most important are eating too much salt, drinking too much alcohol, being obese and, surprise, surprise, taking too little exercise. So you would probably benefit from cutting down salt and alcohol, losing weight and increasing your exercise level. Exercise as simple as walking reduces BP and the higher your BP, the greater the effect. A single bout of exercise reduces BP for several hours, while exercise training reduces BP both at rest and during exercise. This training effect is reflected in a dose-related lowering of the risk of cardiovascular disease (CVD) and premature death at all degrees of hypertension – in other words, the more exercise that is taken, the lower the rate of both CVD and premature death.
After an extensive appraisal of the evidence, the American College of Cardiology concluded that for adult men and women regular aerobic physical activity decreases systolic and diastolic pressure significantly: “The amount of physical activity recommended for lowering BP is congruent with the amount of physical activity recommended in 2008 by the federal government for overall health. Most health benefits occur with at least 150 minutes a week of moderate intensity physical activity such as brisk walking. Additional benefits occur with more physical activity” [my emphasis].
Exercise versus medication
There is a large variety of blood pressure lowering drugs – diuretics, beta-blockers, ACE inhibitors, ARB blockers. Mostly they work by opening up small arteries and reducing the resistance to blood flow.
No trial has directly compared the effect of exercise with that of medication in reducing BP. However, comparative analysis of many trials of both approaches has indicated that exercise does have a very similar effect on blood pressure as medication. The largest meta-analysis carried out compared the results of medication in 29,000 subjects with exercise in 10,000 subjects and concluded that at an individual patient basis medication was slightly more effective, but in groups the average showed no difference.
The effect of exercise on blood pressure is greatest in those who already have hypertension. It is likely that reducing your BP with exercise and other lifestyle changes, such as losing weight and cutting back on salt and alcohol, are more effective at reducing risk than taking pills. Each lifestyle change has many other benefits. Often these can reduce BP sufficiently to allow the previously hypertensive patient to stop taking medication. The American Heart Association has summarised the benefits of exercise as well as other treatments in the management of high blood pressure, concluding that ‘moderate-intensity dynamic aerobic regimens are capable of significantly lowering BP among most individuals within a few months.’
Finally and importantly, hypertension that is resistant to medication can respond to exercise training.
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