Background: Isometric resistance exercises (IREs) have great potential to improve blood pressure (BP) control. However, the effectiveness of IREs in reducing HT is still unknown because their hypotensive effects have not been detected using ambulatory BP measurements (ABPM), which are the current standard for BP measurement.

Methods: This first adequately-powered RCT will involve 390 patients with HT who do not meet the current physical activity guidelines defined by the World Health Organization. Participants will be randomly assigned in a 1:1 ratio using stratified and blocked randomization to either the IRE (wall squat) group or stretching exercise (active control) group. A well-structured, widely accepted, and validated 24-week wall squat program (2 minutes per exercise, 2 minutes of rest between sets, and 3 sessions per week) will be implemented, as it has been commonly used in previous research. Adherence to the program will be monitored using smartwatches, and regular contact with patients through social media will help ensure adherence. All patients will be followed up for 1 year to investigate the long-term effects of IREs on BP. Control group will receive exact same treatment except that IRE is replaced by frequency-matched and time-matched stretching exercise. The primary outcome measure will be systolic daytime ABPM BP at 24 weeks. Secondary outcome measures will include other BP and ABPM parameters at 12 weeks, 24weeks and 1year, cfPWV at baseline, 24 weeks and 1year, and FMD at baseline and 24weeks. Safety data will be collected and reported.

Inclusion Criteria:

• a suboptimal daytime SBP of >135-160 mmHg on a 24-h ABPM
• reported no regular physical activity or less than that recommended for adults by the World Health Organization (e.g. <150 minutes of moderate-intensity aerobic exercise per week)
• on stable doses of anti-HT medication(s) for ≥4 weeks if the patient is receiving drug treatments;
• agree for no drug changes during the intervention period (24 weeks);

Exclusion Criteria:

• cannot provide informed consent
• unwillingness to repeat ABPM
• relative contraindications to ABPM (i.e. diagnosed atrial fibrillation, nighttime workers, occupational drivers, or patients with bleeding tendencies)
• severe osteoarthritis pending knee replacement surgery
• known secondary HT
• use of ≥3 anti-HT medications at maximum doses or ≥4 anti-HT medications
• SBP or DBP are >160 mmHg or >100 mmHg, respectively, on ABPM at baseline or at 12 weeks follow-up to ensure safety
• pregnancy/breastfeeding
• active malignancy