The Effect of Resistance Training on High Blood Pressure

Blood pressure is a key vital sign that describes the force the blood exerts on the walls of the blood vessels. Blood pressure readings are comprised of both the systolic (the “top” number) and diastolic (the “bottom” number) values that correspond to the contraction or relaxation phases of the cardiac cycle, respectively. As of this writing, a normal blood pressure is considered to be < 120 mmHg systolic and < 80 mmHg. A blood pressure of < 90 mmHg systolic and < 60 mmHg diastolic may be considered hypotension (low blood pressure), but this usually requires accompanying symptoms or complications in order to be deemed “abnormal” or to justify treatment.

Prior to 2018, “high blood pressure” was diagnosed when at least two separate readings of ≥ 140/90 mm Hg were measured on at least two separate occasions. All this changed when the American College of Cardiology and American Heart Association’s Task Force on Clinical Practice published their latest guidelines in May 2018.

Current guidelines now describe hypertension as a systolic blood pressure  (SBP) ≥ 130 mm Hg or diastolic blood pressure (DBP) ≥ 80 mm Hg. Additionally, anyone with a SBP ≥ 120 or DBP ≥ 80 is labeled as having elevated blood pressure, though it is still recommended that two or more readings are taken on two or more occasions in order to make this diagnosis. Whelton 2017 Upon publication of these new guidelines, millions of Americans met the new criteria for hypertension or elevated blood pressure … and the 50 billion dollar question is, why? Zhang 2017 

Key Points:

1. Hypertension (high blood pressure) is a significant problem, with roughly 1 in 3 (108 million) adults meeting criteria for the diagnosis. Dorans 2017 Of those with hypertension, less than half are adequately controlled using antihypertensive medications and lifestyle interventions.
2. Exercise, including resistance training, has the potential to improve hypertension across all populations, though individuals with higher blood pressures (who require medications) generally achieved the greatest reductions. 
3. Only a quarter of patients diagnosed with hypertension are counseled to exercise, despite its established efficacy for improving this condition. Mellen 2004

In 2010, hypertension was the leading cause of death and disability-adjusted life years worldwide. In the United States, hypertension accounts for more CVD deaths than any other modifiable CVD risk factor.Lim 2012 Danaei 2009 The authors of the new guidelines have this to say, stressing the importance of obtaining and maintaining optimal blood pressure levels (emphasis ours):

“the risk for CVD increases in a log-linear fashion; from SBP levels of 115 mm Hg to 180 mm Hg, and from DBP levels 75 mm Hg to 105 mm Hg. A 20 mm Hg higher SBP and 10 mm Hg higher DBP are each associated with a doubling in the risk of death from stroke, heart disease, or other vascular disease. In persons greater than 30 years of age, higher SBP and DBP are associated with increased risk for CVD, angina, myocardial infarction (MI), heart failure (HF), stroke, peripheral arterial disease, and abdominal aortic aneurysm.”

Given the large prevalence and risks associated with hypertension, it shouldn’t be surprising that there are many pharmacological and lifestyle interventions available to help prevent, manage, and otherwise treat high blood pressure. For the rest of this piece we’ll focus on how exercise, specifically resistance training, can be used to help manage high blood pressure.

Naci et al. set out to perform the most robust meta-analysis ever performed with respect to the effect of exercise on blood pressure. What’s more, they wanted to compare the effect of exercise on blood pressure to that of antihypertensive medications, which had never been done before. Of the 391 studies the authors included in this review, 197 looked at how various types of exercise influence blood pressure. Prior to this publication the largest meta-analysis on exercise and blood pressure included just 33 separate studies.  The authors had this to say: 

“In this study, we set out to perform a network meta-analysis to compare systematically the SBP-lowering effects of exercise and medications. Our objective was to evaluate how different types and intensities of exercise fared against different classes and doses of antihypertensive medications in terms of lowering baseline SBP levels. In addition, we assessed the comparative SBP-lowering effects of exercise and medications specifically among hypertensive populations.”

Study Design

391 total randomized controlled trials (RCTs) were studied in this meta-analysis. Of those 391 RCTs, 197 were on exercise and 194 were on antihypertensive medications. 

Of the 197 RCTs looking at how exercise affects blood pressure, 115 of them were on aerobic training, 30 were on resistance training, 10 were on isometric training, 12 were on combined aerobic and resistance training, and 30 compared one type of exercise to another.

In these studies the average sample size was 53, with a range of 15-464 subjects. The average age was 50 years old and there were more women (61%) than men. Of note, the average baseline blood pressure was 132 mmHg, which would meet criteria for the diagnosis of hypertension based on current guidelines.

The 194 antihypertensive drug trials included a total of 29281 subjects, with an average age of 55 years and average baseline blood pressure (without treatment) of 150 mmHg. In total there were 39,742 subjects studied in this meta-analysis.

The authors divided exercise interventions into four major categories: 

1. Endurance,
2. Dynamic resistance
3. Isometric resistance
4. Combination of endurance and dynamic resistance

Then, they compared the systolic blood pressure-lowering effects of exercise and antihypertensive medications in three sets of analyses: 

1. All exercise interventions versus all antihypertensive medications
2. Different types of exercise interventions versus different classes of medications
3. Different intensities of exercise interventions versus different doses of medications. 

Finally, they repeated these analyses and compared the antihypertensive drug RCTs to a subset of exercise trials that only included hypertensive populations. This is an important distinction given the higher average baseline systolic blood pressure in the antihypertensive drug RCTs compared to the exercise RCT’s, 150 mmHg compared to 132 mmHg, with many of the individuals in the exercise studies having normal blood pressure.

Therefore, to really tease out how large of an effect exercise can have on blood pressure we would do best to look at how exercise works on patients with hypertension, and compare that to the effect of the antihypertensive medications in a similar population. Fortunately, Naci et al did exactly this in their meta-analysis.

Findings

For all 197 exercise RCTs, which include a large number of people with normal blood pressure, the average decrease in systolic blood pressure was 4.84 mmHg, with the following differences seen between types of exercise:

• Endurance exercise lowered systolic blood pressure by 4.88 mmHg
• Resistance training lowered systolic blood pressure by 3.5mmHg
• Isometric training lowered systolic blood pressure by 5.65mmHg*
• Combined endurance and resistance training lowered systolic blood pressure by 6.49mmHg
• There were no differences in systolic blood pressure lowering effect between medium and high intensity.

*the sample size in the isometric training studies are very small compared to the other sample sizes evaluated here, which may inflate the reported blood pressure lowering effects.

When the authors focused the review of exercise’s effect on blood pressure to only those with systolic blood pressure > 140mmHg, the data showed an average decrease of 8.96mmHg in systolic blood pressure. The following differences were seen between different types of exercise:

• Endurance exercise lowered systolic blood pressure by 8.69 mmHg
• Resistance training lowered systolic blood pressure by 7.83 mmHg
• Combined endurance and resistance training lowered systolic blood pressure by 13.5 mmHg
• There were no differences in systolic blood pressure lowering effect between medium and high intensity. 
• There were no studies done on isometric training in this population.

For all 194 antihypertensive drug RCTs, which included only those with high blood pressure (average SBP of 150 mmHg), systolic blood pressure was lowered by 8.8 mmHg on average. There were no significant differences between types of medications evaluated.

In summary, this meta-analysis suggests that the effect of exercise on systolic blood pressure in those with hypertension is slightly greater than the effect of antihypertensive medications. 

Take-Home Message

Prior to this meta-analysis, the best data we had on resistance training as a form of exercise that could help manage elevated blood pressure were two separate meta-analyses. One by Cornelissen et al reviewed 33 RCTs with 1012 subjects and found that resistance training could lower systolic and diastolic blood pressure by about 3.9 mmHg each. Cornelissen 2011 Zanchetti 2010 The second, a review by de Sousa et al, actually looked at blood pressure changes in those with “prehypertension*” or hypertension.de Sousa 2017 They reviewed 5 RCTs with 201 subjects and it was shown that resistance training lowered systolic and diastolic blood pressures by 8.2mmHg and 4.1mmHg on average, respectively. 

While these data were useful in debunking the idea that strength training increases resting blood pressure, it suffered from relatively small sample sizes (1200 total subjects between the two meta-analyses), and neither directly compared the effect of exercise to the effect of antihypertensive medications.MacDonald 2016 Fortunately, the meta-analysis by Naci et al addresses both of these problems with nearly 40,000 total subjects and a direct comparison of exercise to antihypertensives in patients with elevated blood pressures. We needed this and Naci et al delivered.

Overall, Naci et al’s work strengthens the findings of de Sousa et al as far as how much we think exercise can help when it comes to blood pressure lowering in folks with elevated blood pressures. Furthermore, it provides additional ammunition when it comes to counseling patients, particularly if they do not want to be on multiple medications to control their blood pressure indefinitely. By having a larger evidence base available that suggests exercise – including resistance training – can match antihypertensive medications’ effects on blood pressure, I’m hoping we will see an increase in the frequency exercise is recommended for managing blood pressure. The current rate is 26% and I think we can do better. Mellen 2004

References:

1. Naci H, Salcher-Konrad M, Dias S, et al. How does exercise treatment compare with antihypertensive medications? A network meta-analysis of 391 randomised controlled trials assessing exercise and medication effects on systolic blood pressure. British journal of sports medicine. 2018. 
2. Dorans KS, Mills KT, Liu Y, He J. Trends in Prevalence and Control of Hypertension According to the 2017 American College of Cardiology/American Heart Association (ACC/AHA) Guideline. J Am Heart Assoc. 2018;7(11):e008888. Published 2018 Jun 1. doi:10.1161
3. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults. Paul K. Whelton, Robert M. Carey, Wilbert S. Aronow, Donald E. Casey, Karen J. Collins, Cheryl D
4. MacDonald HV, Johnson BT, Huedo-Medina TB, et al. Dynamic Resistance Training as Stand-Alone Antihypertensive Lifestyle Therapy: A Meta-Analysis. J Am Heart Assoc 2016; 5.
5. Zanchetti A. Looking forward with a grateful heart. J Hypertens 2010; 28:1.
6. Cornelissen VA, Fagard RH, Coeckelberghs E, Vanhees L. Impact of resistance training on blood pressure and other cardiovascular risk factors: a meta-analysis of randomized, controlled trials. Hypertension 2011; 58:950.
7. de Sousa EC, Abrahin O, Ferreira ALL, et al. Resistance training alone reduces systolic and diastolic blood pressure in prehypertensive and hypertensive individuals: meta-analysis. Hypertens Res 2017; 40:927.
8. Mellen PB, Palla SL, Goff DC, Bonds DE. Prevalence of nutrition and exercise counseling for patients with hypertension. United States, 1999 to 2000. J Gen Intern Med. 2004;19(9):917-24.
9. Zhang D, Wang G, Zhang P, Fang J, Ayala C. Medical Expenditures Associated With Hypertension in the U.S., 2000-2013. Am J Prev Med. 2017;53(6S2):S164-S171.
10. Lim S.S., Vos T., Flaxman A.D., et al. (2012) A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 201
11. Danaei G., Ding E.L., Mozaffarian D., et al. (2009) The preventable causes of death in the United States: comparative risk assessment of dietary, lifestyle, and metabolic risk factors. PLoS Med 6. e1000058.