Muscles calm the mind: Exercise can lower stress-related blood pressure responses

In a recent study published in the journal Scientific reports, researchers performed a meta-analysis to elucidate the effects of exercise on stress-related blood pressure (BP) reactivity. Their results show that regular aerobic exercise helps reduce systolic BP responses to adult stressors, especially in hypertensive individuals.

Exercise against stress

Daily life is the source of a myriad of physical, mental and emotional stressors, all of which are known to profoundly affect our internal stability (homeostasis). Previous work has studied the effects of stressors on the cardiovascular system. Stress-related changes in blood pressure have been identified as predictors of future hypertension, rapid aging, and cardiovascular trauma.

Stress is a complex and multidimensional set of factors that threaten homeostasis. Research has suggested that physical and mental stressors could trigger an increase in blood pressure via hormonal, neural network or autonomic alterations. Healthcare providers often prescribe exercise as a nonpharmacological intervention against high BP, with previous research showing attenuated peak BP post-exercise reactivity (acute exercise).

The literature, however, remains devoid of work on non-aerobic exercise and the effects of physical fitness (extended exercise training) on ​​BP responses to stressors. The present work aims to fill these knowledge gaps using a meta-analytic approach to investigate whether physical training can have effects similar to acute exercise. Can routine and regular exercise be used not only as post-stress therapy, but also as a preventative measure against the cardiovascular impacts of stressors?

About the study

The researchers first scanned five electronic databases, identifying 5,058 publications that matched their essential requirements for exercise and blood pressure monitoring. These publications were reviewed and, of them, 23 full publications and one conference abstract were chosen to comprise the final dataset.

All documents were reviewed in duplicate by independent researchers. The meta-analyses included 1,121 individuals recommended between six and 52 weeks of moderate to high-intensity exercise. The duration of the exercise was found to average 50 minutes and was repeated three to four times a week. The ratio of male to female patients was 1.65:1. Nearly 22% of participants were classified as hypertensive, over 61% were normotensive, and the remainder were unclassifiable due to study-specific missing data.

The most prescribed exercise modality was aerobic training, with 21 of 23 studies referencing it. This was followed by resistance training (five studies), yoga (two studies), and isometric hand training (one study). The almost ubiquitous conclusion across all studies has been that exercise is good for you: 10 studies found significant reductions in diastolic blood pressure (DBP), nine in systolic blood pressure (SBP), and one in mean blood pressure responsiveness. Only one paper found a negative association between DBP and yoga.

The most frequent stressor used in these papers was the arithmetic task, which the authors caution because it does not accurately reflect everyday stressors.

Study results

Meta-analyses found that 64% of studies showed positive results where exercise training reduced SBP or DBP. Studies that showed SBP clarified exercise-associated peak stress had moderate favorable effects compared with studies that measured and reported change in baseline BP, which had no impact.

This could indicate that exercise, rather than reducing the stress response, lowers resting blood pressure and, given the same magnitude of the stress response, lowers peak blood pressure.

Despite these findings, blood pressure reduction is still critical, given its association with the risk of future cardiovascular harm, including stroke. The results also suggest that exercise may have different anti-stress effects depending on the type of stressor: physical stressors have been shown to act through arteriolar vasoconstriction. Conversely, a mental stressor would result in no change in blood volume but significant changes in heart rate, heart rate, and blood pressure.

Previous studies have shown that the variance in patients’ familiarity with the tests, self-efficacy, and the post-exercise duration in which the readings are noted could introduce significant heterogeneity in the results. Further work on different stressor modalities, non-aerobic exercise investigations, along with standardized testing protocols could help advance this field further.

Unlike previous work, the current research has not found strong associations between age group and gender for the benefits of exercise. While the younger groups showed no effect compared to the moderate impact seen in the older groups, the differences between the older age groups were insignificant. This study also found more significant improvements in female stress response after exercise, compared to previous literature, which suggested that males benefited more.

Finally, despite little research comparing trends in hypersensitive versus normotensive patients, the present research found evidence that the effects of exercise are greatest for these at-risk individuals. Hypertensive individuals have been found to have lower cardiac output and more significant vascularity than their normotensive counterparts. The relative contributions of exercise and antihypertensive drugs need to be investigated in future work.

Conclusions

The present meta-analysis provides evidence suggesting that aerobic exercise may reduce systolic blood pressure responses to laboratory stress tests. These findings are particularly important for individuals with hypertensive histories and for those over the age of 35. While having the limitation of being limited to secondary data, this study forms the basis for future work.

Future studies should consider exploring different aspects of population characteristics, type of stress test, and other modalities of exercise, especially resistance training.