Effects of HIIT and HIIT plus Resistance Training on Cerebral Blood Flow and Other Health Outcomes in Individuals with Coronary Artery Disease: The Heart-Brain Randomized Controlled Trial

Background: Individuals with coronary artery disease (CAD) are at higher risk of cognitive decline and dementia, in which gray matter cerebral blood flow (CBF) plays a critical role. This study investigated the effects of High Intensity Interval Training (HIIT) and HIIT plus resistance training (RT) on CBF and other health outcomes in individuals with CAD. Methods: This trial included 105 participants with CAD (age 62.1 (SD 6.6) years, 21% women) randomly assigned to HIIT+RT (n=37), HIIT (n=35) or usual care (n=33). The primary outcome was the change in global CBF from baseline to 12-week follow-up. Secondary outcomes included: region-specific CBF (hippocampus, precuneus, and anterior/posterior cingulate cortex), cognitive function (general cognition, episodic memory, processing speed, working memory and executive function/attentional control), peak oxygen uptake (VO2peak), muscular fitness (30s sit-to-stand) and body composition [weight, body mass index (BMI), and fat and muscle mass). Data were analyzed using available-case intention-to-treat constrained (baseline-adjusted) linear mixed models. Predefined subgroup analyses were conducted for age, sex, education, and baseline level of the outcome studied. Results: No significant between-group differences were observed in CBF changes in the whole sample. However, participants with lower CBF at baseline showed greater CBF increases in the HIIT group compared to both usual care (+7.1 ml/100g/min, P=0.02) and HIIT+RT (+5.53 ml/100g/min, P=0.04). No effects were observed on regional CBF or cognition. Both exercise groups improved VO2peak compared to usual care (HIIT+RT: +2.6; HIIT: +2.5 mL/kg/min, both P<0.001). Only HIIT+RT increased muscular fitness (vs usual care: +3.3; vs HIIT: +3.1 repetitions, both P<0.001), and only HIIT decreased BMI (vs usual care: -0.47; vs HIIT+RT: -0.44 kg/m2, both P<0.03). No life-threatening events or deaths occurred during 1995 training sessions in the exercise groups, nor in the usual care group. Conclusion: Twelve weeks of HIIT+RT or HIIT did not increase CBF in the whole sample with CAD, but HIIT effectively increased CBF in those who had poorer CBF at baseline. While no cognitive benefits were observed, we found exercise-specific improvements in other clinically relevant outcomes, such as VO2peak, muscular fitness, and BMI.