Effectiveness and mechanisms of isometric resistance exercise to reduce blood pressure in a Chinese population: study protocol for a randomized-controlled trial

Background Isometric resistance exercise training (IRT) involves sustained muscle contractions without changes in muscle length and joint angle, such as wall squats. Patients with hypertension may prefer IRT because they are easy to learn, require no equipment, are convenient, time-efficient, and can be performed anywhere. However, IRT have not shown to reduce blood pressure (BP) as detected by ambulatory BP measurements (ABPM), the reference standard for BP measurement. This study aims to examine the effectiveness of an IRT program in reducing BP. Methods This randomized controlled trial (RCT) will involve 390 patients with a suboptimal daytime systolic BP of > 135–160 mmHg on a 24-h ABPM, who do not meet the current World Health Organization recommendations for physical activity. Participants will be randomly assigned to either the IRT (wall squat) group or stretching exercise (active control) group (1:1), using stratified and blocked randomization according to age (< 45, 45– < 60, and ≥ 60 years old), sex, and anti-hypertensive drug use (users versus non-users). Investigators will be blinded to randomization sequence and allocation. IRT group will receive a well-structured, widely accepted, and validated 24-week wall squat program (2 min per exercise, 2 min of rest between sets, and 3 sessions per week). Adherence will be monitored by regular patient communication via social media. The control group will receive the same treatment, with the exercise replaced by frequency-matched and time-matched stretching exercise. The primary outcome measure will be systolic daytime ABPM at 24 weeks. Secondary outcome measures will include other BP and ABPM parameters at 12 weeks, 24 weeks, and 12 months, carotid-femoral pulse wave velocity at 24 weeks and 12 months, and flow-mediated dilation at 24 weeks and 12 months. Safety data will be collected and reported. Discussion This trial will be the first adequately powered RCT to determine whether IRT can be recommended as a treatment for hypertension, involving a Chinese population. It will also contribute new knowledge regarding the mechanisms of IRT. This research has the potential to influence clinical practices. If positive results are obtained, this research could potentially alleviate the substantial burden on healthcare systems caused by poor BP control. Trial registration ClinicalTrials.gov NCT06510998. Registered on July19, 2024.