Effects of a short burst of high-intensity exercise versus moderate-intensity exercise combined with restriction to blood flow to the exercising leg muscles on cardiovascular health in people with a combination of risk factors of cardiovascular disease (metabolic syndrome)

Thirty males and females (aged 30 to 65 years) with metabolic syndrome (MetS) will be recruited and randomised to participate in either the: i) reduced exertion high-intensity interval training [REHIT]; ii) moderate-intensity exercise with blood flow restriction (BFR moderate-intensity exercise); and iii) waitlist control. This trial will consist of two phases. The first phase will require the participants to attend one supervised training session to determine the acute effect of the exercise interventions. Assessments will include measures of central arterial stiffness, metabolic syndrome severity, cardiorespiratory fitness, and cardiac autonomic function. Participants will then enter the second phase of the trial and will continue with the same exercise program from Phase 1, but conducted 2-4 times per week (Weeks 1-2 = 2 days; Weeks 3-4 = 3 days; Weeks 5-8 = 4 days) until the 8-week follow-up. Following Phase 2, participants from the waitlist control group will be re-randomised into either of the exercise groups. The participants will be tested at baseline, after a single exercise session, and after 8 weeks follow-up. Written informed consent will be obtained from all participants before inclusion. All participants will receive verbal and written information about their exercise training intervention. Intervention (Exercise Training) The study will consist of 2 exercise intervention groups; 1) REHIT and 2) BFR moderate-intensity exercise. All exercise sessions will be supervised by Accredited Exercise Scientists in groups (maximum of 3 participants per Accredited Exercise Scientist) within the participants' workplace. Exercise heart rate (HR), RPE, and volume (intensity, duration, and frequency) during the trial will be monitored and recorded. HR and RPE will be monitored via a HR monitor (Polar Electro, Kempele, Finland) and the Borg 6-20 RPE scale, respectively. Attendance and compliance with the interventions will also be recorded in a logbook. Exercise Interventions REHIT CAR.O.LTM cycle ergometer units developed by Integrated Health Partners (London, UK; https://carolfitai.com/) will be placed in the workplace environments in order for participants to conveniently perform the exercise intervention. Each REHIT session will utilize the intense 10-min ride option on the cycle ergometer consisting of a 3 min warm-up, 20 s sprint, 3 min active recovery (slow pedal), 20 s sprint, and 3 min cool-down. BFR moderate-intensity exercise Each BFR moderate-intensity exercise session (10 min) will follow the same format as REHIT, which will also consist of a 3 min warm-up, 20 s sprint, 3 min active recovery (slow pedal), 20 s sprint, and 3 min cool-down on a cycle ergometer. The target HR will be established in the following manner: Target HR = HR range of 10-20 bpm (above VT1 and below VT2). Pressure cuffs (~18 cm wide) will be applied on the proximal portion of both thighs as per the current guideline. The cuff belts will be inflated to 140 mmHg during the 20 s sprints of the protocol and deflated during all other periods (warm-up, active recovery, cool-down periods)