OVERVIEW OF HYPERTENSION
Hypertension (HTN) is defined as blood pressure (BP) that is greater than the normal range (see Sidebar). It is a chronic medical condition that increases risk of stroke, coronary artery disease, heart attack, heart failure, peripheral artery disease, and kidney disease (4). Guidelines are based on the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure and are outlined in the Sidebar at right. HTN is a disease that often lacks symptoms and is called “The Silent Killer.” The diagnosis of HTN is usually simple and requires no more than a regular checkup with a physician.
Pre-HTN is not considered a disease category (4). It is a category that identifies persons at high risk of developing HTN. The goal for persons with pre-HTN is to lower BP with lifestyle changes (e.g., weight loss if needed, increased physical activity) and prevent the progression to HTN (4). Drug therapy may be initiated in persons with pre-HTN if other medical conditions are present (e.g., diabetes), and lifestyle modifications are unsuccessful at reducing BP to 130/80 mmHg or lower (4). For persons with stages 1 and 2 HTN, the treatment is a combination of medication(s) and lifestyle modifications (4).
EPIDEMIOLOGY OF HTN
Among the U.S. adult population, the combined prevalence of HTN and pre-HTN is estimated to be approximately 57%, with 29% having HTN and 28% having pre-HTN (26). Approximately half of the first and third leading causes of death in the U.S. (heart disease and strokes, respectively) are associated with this malady. According to the World Health Organization, deaths associated with HTN were much more prevalent than deaths associated with other traditional cardiovascular disease (CVD) risk factors such as tobacco use, dyslipidemia, and overweight/obesity (7). In addition to these traditional risk factors, demographic variables also must be considered as they too may play a key role in health outcomes.
There is a positive association between BP and age (BP increases as people get older) (5,28). There also are some interesting differences between men and women. According to the Framingham Heart Study (12), men demonstrate a sharper rise in BP as they get older when compared with premenopausal women; however, postmenopausal women demonstrate this sharper increase with age. When considering race, it is well established that African Americans have the highest prevalence of HTN in the United States (10). Additionally, a family history (genetic phenotype) of HTN may increase the risk of certain individuals developing HTN (14). Independent of demographics, leading a healthy lifestyle, which includes regular exercise, including resistance training (RT) (e.g., lifting weights, Nautilus), and greater levels of daily physical activity can help ameliorate many chronic maladies including the lowering of BP.
A review by Hagberg et al. (9) illustrated that regular exercise and physical activity can lower systolic and diastolic BP by approximately 11 and 8 mmHg, respectively. A meta-analysis by Kelley and Kelly (13) showed that both resting systolic and diastolic BP were attenuated by approximately 2% and 4%, respectively, after participation in progressive resistance exercise programs. Stewart et al. (29) reported a significant decrease in diastolic BP among older adults (aged 55 to 75 years) after 6 months of combined aerobic and resistance exercise. However, in this study, reductions in BP also were associated with favorable changes in body composition. In a study using individuals with type 2 diabetes, resistance exercise resulted in a greater reduction in BP during the 24-hour postexercise period when compared with aerobic exercise (25). Additionally, in a group of persons with pre-HTN or HTN, Harris and Holly (11) reported that after 9 weeks of circuit-type resistance exercise training, systolic BP was unchanged, and diastolic BP was reduced by approximately 5% (95.8 to 91.3 mmHg). Continued research in this area is needed, but professional medical societies (e.g., American College of Sports Medicine (ACSM), American Heart Association) now recognize the importance of resistance exercise and its favorable impact on health.
The ACSM’s position stand on exercise and HTN recommends individuals with HTN engage in 30 minutes or greater of continuous or accumulated physical activity on most, if not all, days of the week, primarily of the endurance type (28). They additionally recommend RT or muscular strengthening activities, for which there is a paucity of information in the literature when contrasted to aerobic or endurance type activities. Exercise professionals can play a major role in properly managing persons with HTN by stressing the benefits of lifestyle modifications, which include regular structured exercise and increased daily physical activity (e.g., taking the stairs, walking more).
The U.S. Department of Health and Human Services (DHHS) physical activity guidelines for Americans (30) recommend that all Americans engage in at least 150 minutes of moderate-intensity physical activity or 75 minutes of vigorous-intensity physical activity per week, or an aggregate of both. In addition, the guidelines recommend including two or more days per week of resistance or muscular strengthening activities. Currently, adults in the United States who report having HTN have been found to be 15% less likely to meet the new DHHS physical activity recommendation (5). When examining total physical activity volume (minutes), the new DHHS recommendations for all Americans are similar to the ACSM position for persons with HTN or pre-HTN.
RT BENEFITS AND RISKS FOR INDIVIDUALS WITH HTN
There is broad support from major health organizations for the inclusion of RT as a component of lifestyle modifications directed at improving health and fitness of both healthy people and patients with chronic disease (1,2,27,31,33). The majority of this support arises from the recognition that participation in regular RT exercise is the most effective method of improving musculoskeletal function (muscle size, strength, endurance, and power). Although the impact on musculoskeletal function may be reason enough for the inclusion of a properly designed RT program in the exercise prescription provided to persons with HTN, there is sufficient evidence that RT also may favorably impact the prevention and/or progression of this CVD risk factor (11,13,25,29,32).
A meta-analysis examining the effects of chronic dynamic RT on resting BP, which included 320 male and female adults with normal BP and HTN, found statistically significant decreases in both systolic and diastolic BP of approximately 3 mmHg (13). The acute effect of RT on ambulatory BP has not been investigated extensively. Melo et al. (23) found a significant decrease in ambulatory BP for 10 hours after exercise in women with HTN receiving captopril (angiotensin-converting enzyme [ACE] inhibitor), who completed 18 sets of low-intensity RT (40% 1-rep maximum [1-RM]). Although the contribution of RT to cardiovascular health is not as clear as with aerobic exercise, the chronic adaptations seem to be positive (11,13,25,29,32).
The reason for concern with incorporating RT into the exercise prescription in persons with HTN relates to the BP response during the activity itself (acute BP response). To fully appreciate this concern, one must first understand the BP response to aerobic and isometric exercise. During aerobic exercise, there is a “volume load” on the heart and cardiovascular system, with an increase in cardiac output (increase in both stroke volume and heart rate) and a decrease in peripheral vascular resistance (17). This volume load results in a progressive rise in systolic BP with no change or a slight decrease in diastolic BP. During isometric exercise, there is a “pressure load” on the heart and cardiovascular system, with a slight increase in cardiac output (slight increase in heart rate with no change in stroke volume) and an increase in peripheral vascular resistance (17,24). This pressure load results in an increase in both systolic and diastolic BP that is proportional to the relative force exerted during the isometric contraction (24). During dynamic RT, the BP response is a combination of the volume load response of aerobic exercise and the pressure load response of isometric exercise. Braith and Stewart (3) characterized the severity of the pressure load as being dependent on three factors: magnitude of relative resistance (percent of one repetition maximum [%1-RM]), size of the working muscle mass, and duration of the muscle contraction relative to the intervening rest between repetitions and sets.
MacDougall and colleagues (19) generated attention to the BP response in RT exercise when they reported extremely high systolic and diastolic BP responses to maximal and near maximal lifts in young RT bodybuilders. Maximal values reached 480 mmHg for systolic BP and 350 mmHg for diastolic BP on the leg press exercise with lifts continued to maximal volitional fatigue (19). Additionally, the BP response to leg press exercise with one leg was less than that with two legs, and the BP response to one arm was less than the BP response to one leg highlighting the importance of the quantity of muscle mass being contracted on the RT BP response (19).
In a review on RT safety, McCartney (22) also includes number of repetitions and joint angle as factors that affect the severity of pressure load. A recent study of hypertensive older adults revealed a higher BP response when subjects performed 15 repetitions with 50% 1-RM than when they performed a single 1-RM lift (18). Additionally, in a group of cardiac patients, Lamotte and colleagues (16) found a higher BP response to high repetitions with light loads (17 repetitions with 40% 1-RM) than moderate repetitions with moderate loads (10 repetitions with 70% 1-RM). This highlights previous findings among young healthy adults that BP increases progressively as effort increases from submaximal toward maximal effort. Furthermore, even with lighter loads, there is an additive effect on BP with each successive submaximal repetition and set (17). There also is evidence that the BP response during RT varies based on the effort needed to overcome an unfavorable joint position (20). BP response to the leg press was found to be the highest when the knee joint angle was at 90% (leg extensors at their weakest point on the strength curve, requiring a greater relative effort to move the weight) and continually decreased as the legs began to straighten toward full extension (moving through the strongest point on the strength curve).
The speed of movement during the repetition, rest between sets, and number of sets completed with the same exercise have all been shown to affect the BP response to RT in cardiac patients (15,16). The lowest BP response was observed at relatively fast but controlled repetition speeds (one second concentric and one second eccentric) (15). Additionally, the BP response during the third set of the same activity was significantly higher than the first set when rest periods between sets was 30 and 60 seconds but not when rest between sets was 90 seconds or higher (15,16). Therefore, it is becoming clear that safe and effective exercise programming for persons with HTN must address all of the following RT exercise variables: load, repetitions, repetition speed, rest, number of sets, and size of muscle mass recruited.
BASIC PHARMACOLOGY FOR HTN
There are a number of different classes of medications used for the treatment of HTN, which work differently (varying mechanisms) to lower BP. These medications also can affect the exercise response in various ways. See Table 1 for a summary of the more common antihypertensive medications (often referred to as the A, B, C and Ds of HTN), their actions and potential side effects/exercise effects.
RT RECOMMENDATIONS FOR INDIVIDUALS WITH HTN
It is prudent that anyone with HTN check with their physician and be medically cleared to exercise independently before starting an RT program. As discussed earlier, people with HTN may be taking a number of medications for HTN and possibly other health conditions, which may affect RT and overall exercise performance. Also, individuals may have concomitant health conditions (e.g., uncontrolled heart arrhythmia) that will preclude safe participation in an RT program. There are specific RT guidelines for persons with HTN (Table 2) (1,2,33).
These recommendations are general and may need modifying, based on the person’s abilities, health condition, time constraints, goals, and so on. For example, if an individual’s goal is to increase muscular strength, gradually progressing to heavier loads (e.g., 70% to 75% 1-RM) may be appropriate as long as resting and exercise BP remain within the recommended limits. Manipulation of chronic RT variables (e.g., periodization) should be considered for long-term progression and the avoidance of training boredom.
RT in people with HTN can be performed in a circuit-training format (lighter resistance, shorter rest periods) or in a more conventional format (e.g., light-moderate resistance 40% to 60% 1-RM, longer rest periods). Data indicate no significant difference with changes in resting BP when these two styles of RT were compared (6,13). However, longer rest periods (Table 2) may be needed to allow BP to return to baseline levels after each RT exercise/set (15,16). This is an important consideration in people with HTN or pre-HTN.
Initial strength testing (e.g., 1-RM) may not be appropriate in this population because of its high-intensity nature. However, after an initial adaptation period (e.g., 4 to 8 weeks), 1-RM testing may be appropriate and effective. A safer initial method for determining appropriate loads is to use a rating of perceived exertion (RPE) scale, keeping the subjective effort within the recommended ranges throughout the set (Table 2). What is most important is that the load/resistance used allow the person to complete the desired number of repetitions (8–10) in a submaximal manner.
To ensure BP is controlled in people with HTN, measuring resting BP preexercise and postexercise should be performed at each RT session. A preexercise measurement will help determine compliance with medication protocol and ensure BP is not too high for RT. A postexercise measurement can show reductions in BP, which will likely motivate the individual to continue with their exercise program. Exercise BP measurements should periodically be performed during an RT exercise, to ensure that excessive rises in BP do not occur during RT. This is most easily accomplished during a seated lower body exercise, such as a leg press or leg extension machine. Take the BP measurement near the completion of the set to obtain a peak or near-peak exercise BP. ACSM recommends maintaining BP ≤220/≤105 mm Hg during exercise (2).
HTN affects millions of Americans and is a significant contributor to premature morbidity and mortality. An exercise program designed to help manage HTN should emphasize aerobic activities. However, RT can play an important role in the lifestyle management of HTN and should be a component of a comprehensive exercise program designed to address the broader health and fitness goals of people with HTN. Given the increased risks associated with RT for persons with HTN, it is prudent that the exercise professional take a conservative approach (especially initially) when implementing and monitoring a RT program for someone with controlled HTN. Recommendations presented in the article will help promote safe and effective RT programs in people with controlled HTN.
Disclosure: The authors declare no conflicts of interest and do not have any financial disclosures.
CONDENSED VERSION AND BOTTOM LINE
HTN is a common CVD affecting more than 25% of the U.S. adult population. Lifestyle intervention plays an important role in the management and prevention of HTN. Part of the lifestyle intervention should be performing regular RT. When the proper guidelines are followed, RT performed in a submaximal manner has been shown to be safe and beneficial for persons with controlled HTN.
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