RecruitingBehavioural interventionBreaking Sitting with High-intensity Interval Training for Brain HealthThis trial will examine whether interrupting 3.5 hours of sitting every 30 min with 6 min high intensity interval training (HIIT) breaks compared to light intensity interval training (LIIT) will improve brain health in cognitively normal older adults. This trial will test the feasibility of HIIT breaks to sitting. It will also address several important but unanswered questions: (1) Does interrupting sitting with short HIIT breaks improve frontoparietal function? (2) Can interrupting sitting with HIIT breaks improve cognitive functions?