Exercise Prescription for Hypertension

The importance of physical exercise in preventing, treating and controlling hypertension has been the subject of enormous attention during the past several decades. Nearly one third of American adults have been diagnosed with high blood pressure and millions more have pre-hypertension. Cardiorespiratory fitness (CRF) has an important non-pharmacologic role in hypertension treatment and prevention, yet one in three Americans does not engage in leisure-time physical activity.


Introduction
As early as 1925 elevated blood pressure was associated with higher mortality [1].Hypertension is a major risk factor for cardiovascular death in every region of the world [2] and is the most common, costly, but preventable cardiovascular risk factor [3].
The American Heart Association estimates that about 103 million US adults (45.6%) have high blood pressure as defined as equal to or greater than 130/80 mmHg [4].Another 87 million have prehypertension ≥ 120-130 systolic and/or diastolic ≥ 80-< 90.
Continuous improvements in cardio-respiratory fitness provide the lowest risk of hypertension [5].High levels of muscular strength appear to protect hypertensive men against all-cause mortality, and this is in addition to the benefit provided by cardiorespiratory fitness [6].
In 18 years of follow-up of 2,346 men without hypertension initially, both physical activity and CRF were associated with lower risk of developing hypertension [7].The principal finding of this report is that both higher CRF and participating in sport or walking/jogging/running decrease the risk of developing hypertension in comparison with low fitness

Evaluation of the Hypertensive Patient Prior To Initiating an Exercise Program
Cardiovascular risk and attendant comorbidities must be assessed to safely begin an exercise program.The presence or absence of target organ damage including peripheral vascular disease and risk factors such as smoking, dyslipidemia, and diabetes must be considered.Since many patients will be found to have comorbidities, a carefully tailored program must be developed for each patient.

Exercise Prescription Design
Using the physician prescription approach as a guide for the "dose" of exercises one must consider in most patients beginning an aerobic exercise program the mode, intensity, pattern, duration and frequency of exercise.

Aerobic
Mode: Exercise that involves large muscle groups (legs, arms, trunk) that is continuous and rhythmic in nature (e.g., brisk walking, jogging, running cycling, swimming, rowing, cross-country skiing, climbing stairs, active dancing).
Intensity: Moderate and/or vigorous intensity relative to the person's capacity recommended for most healthy adults: 55/65%-90% of HR max (maximum heart rate determined or predicted).Light to moderateintensity exercise is of benefit in deconditioned or older people.Higher percent effort may be needed in highly fit people to improve cardiorespiratory fitness (CRF).
Pattern: Exercise may be performed in one (continuous) session per day or in multiple sessions per day of ≥ 10 min each to accumulate the desired amount of exercise per day.Exercise bouts of ≤ 10 min may yield favorable adaptations in deconditioned individuals.High-intensity interval training can be effective in adults with good exercise tolerance.
Duration: 30-60 min of continuous or intermittent (10 min bouts) throughout the day with a combination of moderate and vigorous exercise for most active adults.Moderate intensity activity of longer duration is recommended for adults with comorbidities.observed that "in the general population, arterial pressure rises with age".

Co-Morbidities
Hypertension is associated with several co-morbidities of which the most prevalent are obesity, dyslipidemia, and impaired fasting glucose.

Sequela of Hypertension
As described by Schiffrin [12], hypertensive vascular disease involves both large and small arteries as well as arterioles and is characterized by thickening of the intima and media with luminal narrowing.Moreover, hypertension appears to increase the susceptibility of the small and large arteries to atherosclerosis.Thus, hypertension is a major risk factor for all clinical manifestations of atherosclerosis e.g., heart failure, coronary artery disease, stroke, renal disease and peripheral vascular disease.
According to the CDC [14] coronary artery heart disease accounts for 1 in 7 deaths in the U.S. annually.Further, stroke is a leading cause of long-term disability and accounts for 1 of 19 deaths in the U. S. CHD can cause LVH and vice versa.With CHD, the heart must work harder to eject blood and may compress the coronary arteries.According to the CDC [14], about 7 of every 10 people having their first heart attack have high blood pressure and 8 of every 10 people having their first stroke have high blood pressure.Further, about seven of those with chronic heart failure have high blood pressure and approximately 50% of deaths are a result of high blood pressure.

History of Exercise and Hypertension Research
Ebers papyrus, an Egyptian compilation of medical texts dated about 1550 BC, is one of the oldest known medical works.It was acquired by George Maurice Ebers a German Egyptologist and novelist, in 1873 [15].The 110-page scroll contains 700 magical formulas and folk remedies meant to cure afflictions ranging from crocodile bite to toenail pain and to rid the house of such pests as flies, rats, and scorpions.It also includes a surprisingly accurate description of the circulatory system, noting the existence of blood vessels throughout the body and the heart as center of the blood supply.

Patient Assessment
The diagnosis of hypertension is commonly made from at least three separate visits where the readings are averaged.Some have suggested readings over five separate visits with average SBP of 140 or greater and the DBP 90 or greater [16].Ambulatory Home blood pressure is recommended to confirm office-based measurements which may be falsely elevated (white coat hypertension) [17].
Frequency: A combination of moderate and vigorous exercise on 3-5 d/wk.Progression: A gradual progression of exercise volume by adjusting exercise duration, frequency, and/ or intensity is reasonable until the desired exercise goal (maintenance) is achieved.Gradual progression may reduce risks of musculoskeletal injury and adverse CVD events.
As supervised aerobic exercise is begun, blood pressure response should be periodically measured to ascertain the effect during and post-exercise.It is not unusual to observe dramatic increases or decreases in blood pressure measurements -a finding which may require additional cardiovascular evaluation.

Resistance Training
While possibly counter intuitive, resistance (strength) training is recommended as an additional component to aerobic exercise in primary and secondary cardiovascular disease prevention programs.While resistance training does cause and increase in both systolic and diastolic blood pressure while lifting, researchers have reported a decrease in resting blood pressure for up to 10 hours following low-intensity resistance training in hypertensive patients (40% of 1 repetition maximum 3 × 20.However, persons with resting blood pressure of 180/110 or higher should not perform resistance training without physician clearance [19].

Summary
Hypertension is a major risk factor for death throughout the world.In the United States, approximately 70% of heart attack victims have hypertension.Hypertension has been listed on nearly 50% of death certificates as the primary cause of death.Death rates per 1,000 people are 42% higher in those with high blood pressure compared to those with normal blood pressure according to the NHANES III study [20].Cardiorespiratory fitness (CRF) is demonstratively associated with prevention and/ or control of hypertension.Unfortunately, as noted, fewer than one in three Americans engage in leisuretime physical activity and only 24% of adults fully meet physical activity guidelines for aerobic and muscle strengthening activities according to the CDC [8].