Chronic Hypertension is a medical condition also known as high blood pressure, where the pressure exerted on the arterial walls is significantly increased, specifically to ≥140 mm Hg systolic blood pressure or ≥90 mm Hg diastolic blood pressure1. This causes the heart to work harder and increase the effort of its contraction to pump the blood out of the ventricles and to circulate the rest of the body. Hypertension is divided into two categories, either Primary or Secondary hypertension. Primary hypertension is the most common form of high blood pressure and accounts for 90-95% of cases, although the causes for this type are not fully understood. The other form is known as secondary hypertension and can be caused by one or a combination of factors, such as genetic predisposition, environmental factors and diet, but these can be improved by adopting certain lifestyle changes in diet and exercise.
The higher blood pressure is, the greater the chance of heart attack, heart failure, stroke, and complications with the pressure within the eye and kidney diseases.
= Who does it affect? =
Hypertension is an extremely common cardiovascular disease with more than 1 billion individuals worldwide living with the disease and approximately 7.1 million deaths per year may be the result of chronic hypertension. The prevalence of hypertension increases with advancing age to the point where more than half of people aged 60 to 69 years old and approximately three quarters of those aged 70 years and older are affected. According to longitudinal data obtained from the Framingham Heart Study, people with blood pressure values in the range of; systolic 130 to 135/85 to 90 mmHg diastolic were at double the risk of a serious cardiovascular disease, compared to those with normal blood pressure of 120/80 mmHg.
= Prescription of resistance training =
The lowering of blood pressure and prevention of hypertension is in first instance preferable by lifestyle changes, before the administration of any drugs / medication. Such lifestyle changes may include weight loss, reduction of alcohol intake, a diet with increased fresh fruit and vegetables, reduced saturated fat, reduced salt intake, and, finally, increased physical activity. In regard to the last option of lifestyle changes, physical activity through endurance training has proved to reduce resting heart rate, increase stroke volume, and decrease the peripheral resistance on vessels. Although endurance training is beneficial, a few studies show evidence that Resistance Training (RT) can also have an influence on reducing the effects of hypertension over long duration. The methods of RT prescribed to prehypertension and hypertensive patients are divided into 2 subgroups; dynamic and isometric (static) training.
Dynamic RT involves the change in length of the muscle as well as constant tension with each concentric and eccentric contraction. Static movements are those where the muscle length does not change, although constant force is being produced.
When Cornelissen. V, et al conducted their 28 trials, participants were involved in three RT sessions per week for a period of 52 weeks for dynamic RT and separate participants were involved in 10 weeks for isometric RT. The intensity of each of the RT sessions ranged between 30%-100% of one repetition maximum (1RM) for dynamic training, and 30%-40% of 1 maximal volitional contraction against an immovable object. Most of the exercises were performed on free weights or machines and some were performed using resistance bands.
These particular RT methods propose to yield a decrease of 3.9 systolic /3.9 diastolic mm Hg in prehypertensive participants and 4.1 systolic / 1.5 diastolic mm Hg in hypertensives.
= How does RT improve the quality of life for someone with hypertension? =
Depending on the intensity and the duration of each exercise session, dynamic RT may yield considerable benefits in lowering an individual’s cardiovascular risk factors. These may include an increase in peak VO2 and a reduction in body fat and plasma triglycerides.
It is also estimated from large group trials such as the trials conducted by Cornelissen. V, et al that reductions in systolic pressure and diastolic pressure as small 3 mmHg can decrease the risk of coronary heart disease (CHD) by 5% and Stroke by 8%. These statistics indicate that RT may only reduce SBP and DBP by minute amounts but it still has a considerable impact on decreasing the risk of life threatening cardiovascular diseases.
= Limitations and Recommendations =
The exercise trials conducted by Cornelissen. V.A, et al and Mortensen. S.P et al shows a glimpse into the possible benefits that come with prescribed resistance training for prehypertension and hypertensive individuals. This however is limited by the scarcity of documented journals and data from past trials and is hard to relate to the entire hypertensive population. Despite some limitations, such as the lack of research into this area, the few studies provide evidence for the potential of dynamic resistance exercise training over long duration to decrease risk of various cardiovascular diseases, and therefore reduce blood pressure. Only a few groups in the research trials completed involved hypertensive patients; therefore, more research on the effect of RT is definitively needed in hypertensive populations, stressing the need for large, randomized, controlled trials investigating the effect of dynamic and isometric RT on BP and other cardiovascular risk factors and BP-regulating mechanisms that can help us to understand their BP-lowering effect. Until then, some caution is warranted when prescribing RT for hypertensive individuals.
= References =