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Results of a systematic review and network analysis of the relationship between exercise and blood pressure were recently published in BMJ. The final analysis included data from 270 randomized and controlled trials, including nearly 16,000 total participants over a 33-year period of review. This analysis was conducted to update existing guidelines that primarily promote only traditional aerobic exercise to manage resting blood pressure, lacking insight into types of exercise with more recent trial data, including high-intensity interval training (HIIT), isometric exercise training (IET), and independent dynamic resistance training (RT). The trials included in this analysis were limited only to those with exercise as the only intervention, i.e., any trials that also had dietary changes, supplements, or medications as part of the treatment were excluded.
The categories of exercise broadly included aerobic exercise training (subcategories: walking, cycling, running), dynamic RT, combined training, HIIT (aerobic vs. sprinting intervals), and IET (isometric handgrip, isometric leg extension, isometric wall squat). Comparing the effect of each type of exercise on systolic blood pressure (via pair-wise analysis) found that each type of exercise was associated with a significant reduction, with the exception of high-intensity aerobic interval training, which was associated with a small but non-significant reduction.
The mode of exercise associated with the largest decrease in systolic blood pressure was IET, associated with a mean decrease of 8.24 mmHg, with the individual subtypes of isometric leg extension and wall squat having the greatest impact (-10.05 and -10.47 mmHg, respectively). In comparison, traditional aerobic exercise was associated with an overall decrease of 4.49 mmHg, ranging from reductions of 2.85 (walking) to 6.88 (cycling) mmHg in systolic blood pressure. The effect of each type of exercise on diastolic pressure was very similar; again, only high-intensity aerobic interval training did not have a significant effect on diastolic pressure, and the type with the largest reduction was also IET (-4.0 mmHg). However, the subtype with the greatest overall effect on diastolic pressure was running, associated with a 5.67 mmHg decrease.
Results were also stratified by the baseline blood pressure of participants, e.g. normotension, prehypertension, and hypertension, with effects on systolic blood pressure only determined for the broader categories of exercise (not enough information was available to examine the effects on diastolic pressure). For each type of exercise, the reductions in blood pressure were the greatest among participants with hypertension, with the greatest decrease (-11.14 mmHg) among hypertensives in response to combined training (a combination of aerobic and RT), and the largest drop among prehypertensives in response to IET (-10.93 mmHg). IET (-9.22 mmHg), HIIT (-6.59 mmHg), RT (-6.32 mmHg), and aerobic exercise (-7.74 mmHg) all were associated with significant reductions in blood pressure among people with hypertension.
The rank order of effectiveness of each exercise type on systolic pressure (based on the surface under the cumulative ranking curve (SUCRA)) was also calculated, with the most effective calculated to be IET (SUCRA 98.3%, indicating it is likely to be superior to 98.3% of all interventions (exercise-based)), followed by combined training (75.7%), dynamic RT (46.1%), aerobic training (40.5%), and HIIT (39.4%). Isometric wall squats were determined to be the most effective for reducing both systolic and diastolic pressures.
There are a number of takeaways from this analysis. It’s clear that multiple types of exercise are suitable as interventions to lower blood pressure, including RT and combined exercise, and clinicians should not be limited to prescribing only aerobic activity to help reduce blood pressure, as each type of activity was associated with a meaningful decrease among people with hypertension. Among these, the exercise with the greatest efficacy (for reducing both systolic and diastolic pressures) appears to be isometric wall squats, though when analysis is restricted to those with hypertension, combined training may be slightly more effective. Also, when recommending aerobic exercise, there may be quite an advantage to running and cycling compared to walking, with a nearly 2.5-fold difference in their effects on systolic pressure. Similarly, the superiority of sprint vs. aerobic HIIT suggests that higher-intensity exercises may be of greater benefit in this type of exercise as well.
Regarding isometric wall squats, results of a randomized crossover trial recently published in Physiology Reports provide some insight into the mechanism by which they lower blood pressure. A small group of physically inactive men had either a 4-week IET intervention or control period, with a 3-week washout period in between. Hemodynamic data (including continuous systolic and diastolic pressure, resting stroke volume, resting heart rate, pulse pressure, and total peripheral resistance were captured, and the augmentation index was calculated (a measure of systemic arterial stiffness). This study indicates that arterial stiffness was reduced by isometric wall squats, and peripheral vascular resistance was also decreased. Previous work (cited within this study) suggests that a reduction in inflammation and improvement in endothelial function accompany the drop in blood pressure. Wall squats are generally prescribed as 4 sets of 2-minute bouts with 2 minutes of rest in between, with an intensity based either on heart rate (95% heart rate peak method) or the rate of perceived exertion (building from an RPE of 4 to 8.5 over the 4 sets).
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