Exercise and resting BP

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Exercise and Resting Blood Pressure
Len Kravitz, Ph.D.

Article Reviewed
Kelley, G. A., and Kelley, K. S. (2000). Progressive resistance exercise and resting blood pressure: A meta-analysis of randomized controlled trials. Hypertension, 35, 838-843.

Introduction
High blood pressure, or hypertension is a major health problem affecting 43 million Americans, which is approximately 24% of the national population (Kelley & Kelly, 2000). It is defined as resting systolic and/or diastolic blood pressure greater than 140/90 mmHg. There are two million new cases of hypertension each year, and it is estimated that two-thirds of American will have high blood pressure some time in old age (Neiman 1998). This article will examine the impact of aerobic exercise and hypertension and review recent research on the affect of progressive resistance exercise on resting systolic and diastolic blood pressure in adults.

Hypertension the Health Problem
High blood pressure kills more than 37,000 Americans each year and contributes to the deaths of 700,000 individuals (Neiman 1998). When undetected and untreated, hypertension may lead to a number of abnormal problems. The heart sometimes begins to increase in size, which eventually can cause heart failure. The blood vessels in the kidneys often begin to narrow, which may lead to kidney failure. The brain’s blood vessels can develop small wall defects, known as aneurisms, which oftentimes leads to a stroke. Finally, hypertension will sometimes lead to a hardening of the arteries throughout the body, which can provoke a heart attack, stroke, or kidney failure. In population areas and societies where physical inactivity and obesity are present, and salt and alcohol intake are high, hypertension is common (Neiman 1998).

Aerobic Exercise Prescription for Lowering High Blood Pressure
The aerobic exercise prescription for lowering resting blood pressure includes moderately intense aerobic exercise at 40% to 60% of VO2max, for 30 to 45 minutes, on most days of the week. Aerobic exercise is a potent intervention in lowering and preventing the incidence of hypertension. Those with high normal and Stage 1 hypertension (See Table 1) may expect a drop of up to 8 – 10 mmHg and 6 – 10 mmHg in systolic and diastolic blood pressure, respectively, due to the independent effect of aerobic exercise (Neiman 1998). It is interesting to note that most of the lowering of systolic and diastolic blood pressure in those with hypertension occurs within a few weeks of consistent aerobic training. The exact mechanism how aerobic exercise helps to lower high blood pressure is unclear, however it is theorized that biochemical, neural and hormonal changes in the blood vessel walls induce an acute and long-term blood vessel relaxation.

How effective is Resistance Exercise in Lowering Blood Pressure?
The research has been unclear as to the relationship of progressive resistance exercise and those individuals with hypertension. Studies in this area have been criticized for having small sample populations and inadequate research designs. However, Kelley and Kelley (2000) recently employed a powerful quantitative research technique known as meta-analysis, to better ascertain what is truly known about the use of resistance exercise as a nonpharmacological intervention in lowering resting blood pressure in adults. Using this sophisticated statistical design, these researchers concluded that participation in resistance exercise results in decreases of approximately 2% and 4% in systolic and diastolic blood pressure, respectively. The length of training in all the studies was from 6 to 30 weeks, with a mean training period of 14 weeks. Frequency ranged from 2 to 5 times per week, with an average of 3 times per week. The intensity ranged from 30% to 90% 1-RM, with a mean of 35% 1-RM. The duration per session varied from 20 to 60 minutes, with a mean session length of 38 minutes. The number of sets per exercise ranged from 1 to 4, with an average being 2 sets. The number of exercises ranged from 6 to 14 with the mean being 10 exercises. Means for the actual number of repetitions and rest between sets were not reported in all investigations, so this information can only be reported in ranges. The number of repetitions ranged from 5 to 50 repetitions, and the rest between sets ranged from 15 to 120 seconds.

The meta-analysis suggests that progressive resistance exercise has modest reductions in resting systolic and diastolic blood pressure. It is important to note that even small reductions in blood pressure have a beneficial effect in reducing cardiovascular disease morbidity and mortality (Kelley and Kelley 2000). An interesting finding of this investigation was that circuit training protocols result in similar blood pressure changes as do traditional % 1-RM designs. The researchers suggest uttermost caution in prescribing high intensity resistance exercise for those with high blood pressure, as peak systolic and diastolic values of 320 and 250 mmHG have been observed with this type of training.

Final Thoughts
Previously, individuals with hypertension have been counseled not to engage in resistance exercise programs because of fears of an unusually high blood pressure response. However, from this research review, it appears that moderate intensity weight training and circuit training may be recommended as part of an all-around exercise program that will help improve quality of life and reduce cardiovascular disease risk.

Side Bar 1. Blood Pressure Response to Aerobic Exercise
During upright exercise, the normal blood pressure response is to observe a progressive increase in systolic blood pressure with no change or even a slight decrease in diastolic blood pressure. The slight decrease in diastolic blood pressure is due primarily to the vasodilation of the arteries from the exercise bout. Thus, the expansion in artery size may lower blood pressure during the diastolic phase. A failure of the systolic blood pressure to rise with an increase in intensity (called exertional hypotension) is considered abnormal, and may occur in patients with a number of cardiovascular problems. Contrariwise, an increase in diastolic blood pressure of more than 10 mmHg during or after exercise represents an unstable form of hypertension, and may be associated with coronary artery disease. Following exercise, systolic blood pressure progressively declines during an active recovery. With a passive (such as seated) recovery, systolic blood pressure may drop abruptly due to the pooling of blood in the peripheral areas of the body. There may also be a drop in diastolic blood pressure, during the recovery phase of exercise due to the vasodilation. Persons on medications will have variable responses to exercise. Therefore it is prudent to contact their health practitioners to be aware of what would be considered normative under these circumstances.

Table 1. Classification of Blood Pressure for Adults Aged 18 Years and Older*

From the Sixth Report of the Joint Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNCVI), Public Health Service, National Institutes of Health, National Heart, Lung and Blood Institute, NIH Publication No. 98-4080, November 1997.

*Based on the average of two or more readings taken at each of two or more times. When diastolic and systolic blood pressure falls into different categories, the higher category should be selected for classification.

Additional References:
Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. (1997). The sixth report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Archives of Internal Medicine. 157: 2413-2444.

Nieman, D. C. The Exercise-Health Connection. (1998). Human Kinetics.

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