Feasibility randomised controlled trial to assess the delivery of a novel isometric exercise intervention for people diagnosed with uncomplicated stage 1 hypertension in the National Health Service: key quantitative findings

OBJECTIVES: The aim of this study was to determine the feasibility of delivering personalised isometric exercise (IE) for people with stage 1 hypertension. Is it feasible to deliver an isometric wall squat intervention in the National Health Service and what sample size is required to conduct an appropriately powered effectiveness randomised controlled trial (RCT)? DESIGN: Randomised controlled open-label multicentre feasibility study of IE compared with standard care in unmedicated people with stage 1 hypertension. SETTING: Initially, the study aimed to recruit through primary care, but this process coincided with the advent of the COVID-19 pandemic. Therefore, we shifted focus to direct-to-public advertising and delivery in secondary care. PARTICIPANTS: People with unmedicated stage 1 hypertension aged over 18 able to perform IE were included. Patients were excluded if average home systolic blood pressure (sBP) <135 mm Hg; were unable to undertake the study intervention; had a previous history of diabetes mellitus, ischaemic heart disease, moderate-severe valvular heart disease, arrhythmia, stroke or transient ischaemic attack, aortic aneurysm, peripheral arterial disease and uncorrected congenital heart condition; stage 3b chronic kidney disease or worse; heart failure; enrolled in another clinical trial; pregnant or breastfeeding. 41 participants (57±15 years), 59% women, were randomised.Intervention participants were randomised (1:1) to either standard lifestyle advice or an individualised isometric wall squat prescription, performed 4×2-min bouts three times a week for 6 months. PRIMARY AND SECONDARY OUTCOME MEASURES: We assessed deliverability, attrition, adherence and variance in blood pressure (BP) change. RESULTS: IE was found to be easily deliverable to all participants. At 6 months, 34% had withdrawn. Of those who completed IE, 85% of their sessions were at the correct intensity, meeting our retention criterion for success. Variance in BP change was 14.4 mm Hg. The study was not powered to show a difference in BP between groups; however, BP reductions were seen in the intervention group at all study time points compared with baseline. There were no adverse events related to study participation. CONCLUSIONS: We met our a priori recruitment criteria which allowed us to calculate a sample size (n=542) for a full RCT. The results demonstrate good acceptability and adherence rates to the treatment protocol. Our results show a signal towards a consistent sBP reduction in the IE group compared with baseline. TRIAL REGISTRATION NUMBER: NCT04936022 (https://classic. CLINICALTRIALS: gov/ct2/show/NCT04936022?cond=isometric+exercise&draw=2&rank=7); registry identifier: ISRCTN 13472393.