In the news: Isometric Exercise for Lowering Blood Pressure; Could Vitamin D Reduce AFib Risk?

Isometric Exercise for Hypertension

Close to half of US adults have hypertension, defined as a systolic blood pressure greater than 130 mmHg or a diastolic blood pressure greater than 80 mmHg, or are taking medication for hypertension. Since the prevalence is high and the potential health effects (heart attack, stroke, retinal vessel damage) are consequential, research into effective ways to control this condition is ongoing.

Regular exercise is one of the pillars of treating hypertension, along with weight reduction, eating the DASH diet, reducing sodium, and lowering stress. Current recommendations call for at least a half an hour of exercise (aerobic) most days of the week. While many forms of exercise can be beneficial, is there a particular mode of exercise that is optimal for reducing high blood pressure?

To address this question, UK researchers conducted a meta-analysis(1) , analyzing data from 270 randomized controlled trials that included more than 15,800 people. Included trial protocols were stratified as aerobic exercise training (AET), resistance training (RT), combined training (CT), high-intensity interval training (HIIT) and isometric exercise training (IET).

These categories were then further stratified into subgroups: AET included walking, running, and cycling, HIIT included sprint interval and aerobic interval training, and IET included isometric leg extension and wall squats.

While the analysis showed that all modes of exercises were effective at reducing both systolic and diastolic blood pressure, the isometric (IET) was the best. IET showed reductions (in mm Hg) of 8.24/4 compared with 4.49/2.253 for aerobic, 4.55/3.04 for resistance, 6.04/2.54 for combined, and 4.08/2.50 for high-intensity interval training.

All exercise modes significantly reduced systolic pressure in normal blood pressure cohorts, while reductions were larger in those with hypertension.

The study authors conclude that these findings should inform future exercise guideline recommendations for the prevention and treatment of arterial hypertension.

Isometric exercise involves increasing tension in a muscle without moving any surrounding joints. Wall squats involve slowly moving into a squat as the back is pushed against a wall, the position held, then coming back up. Examples of other isometric exercises are side planks, calf raises, low squats v-sits, and glute bridges – exercises that can be seen demonstrated on YouTube, for example.

Vitamin D & Risk of New AFib

Epidemiological studies have linked vitamin D deficiency with increased risk of atrial fibrillation (AFib), but very few randomized trials have looked at the effect of supplemental vitamin D on the incidence of this condition in healthy individuals.

Finnish university researchers conducted a post hoc analysis(2) from a study that examined the effects of vitamin D on CVD and cancer incidence in nearly 2.500 healthy older participants who received either 1600 IU or 3,200 IU vitamin D or placebo daily. The participants were, for the most part, vitamin D sufficient.

AFib developed in 190 participants over an average 4-year follow-up period. The group receiving the lower dose vitamin D had a 27% reduction in AFib risk (HR 0.73, p= .03), while those in the higher dose vitamin D had a non-significant risk reduction.

The risk for AFib was reduced by 30% when both vitamin D dose groups combined were compared with the placebo group. (HR 0.70) p=.02)

The authors point out that the findings should be interpreted cautiously as AFib was not a prespecified primary outcome of the Finnish Vitamin D Trial (FIND), that was analyzed post-hoc.

References

1. Edwards J, et al. Exercise training and resting blood pressure: a large-scale pairwise and network meta-analysis of randomised controlled trials. Br J Sports Med, Epub July, 2023.
2. Virtanen J, et al. The effect of vitamin D3 supplementation on atrial fibrillation in generally healthy men and women: The Finnish Vitamin D Trial. Am Heart J. 254:177-182, 2023.