Randomised controlled effectiveness study (RCT) of isometric exercise (IE) in adults with stage 1 and 2 hypertension – ISOFITTER study [version 2; peer review: 2 approved, 1 approved with reservations]

High blood pressure (BP) affects more than one in four adults in England and only one in three patients are being treated effectively. Treatment of high BP includes changes to lifestyle such as more physical activity and/or taking medication. However, low adoption and high attrition rates are common with current large targets for recommended exercise (>150 minutes moderate exercise per week plus 2 strength sessions). Evidence suggests that isometric exercise (IE), holding a fixed body position for a period of time, for example a wall squat, lowers BP a greater amount, with less time and effort, than other recommended exercise. This ISOFITTER study will provide robust effectiveness evidence of IE for hypertension. A multi-centre, randomised, controlled trial of isometric exercise wall squat intervention for hypertension: an effectiveness-implementation hybrid type-1 design. Adults (n=542) with Stage 1 or Stage 2 hypertension, on no more than one antihypertensive, and no other medical contra-indications will be randomised to either a standard care plus IE intervention group or standard care control group. Blood pressure readings, fidelity measurements, medications, adverse events, quality of life, participant satisfaction and health service use will be collected at baseline, week 4, month 3 and month 6 with a subgroup of n=50 invited up to month 12. Qualitative participant focus groups and interviews with wider stakeholders will collect implementation data. The ISOFITTER study will establish effectiveness of a self-administered, home IE intervention in lowering blood pressure in people with uncomplicated stage 1 and 2 hypertension. Implementation evidence will support patient delivery, context for scaling up of the intervention and intervention cost. Lifestyle changes for the treatment of hypertension in the absence of other risk factors should not be overlooked. For long term hypertension management, easily adopted, evidenced exercise interventions are needed. This study will help to address this evidence gap.