Breaking Sitting with High-intensity Interval Training for Brain Health

The investigators are conducting an acute, single site randomized crossover trial testing two conditions lasting 3.5 hours each with a one to four-weeks washout period: (1) Interrupting sitting with 6 min of high-intensity interval training (HIIT) every 30 min, and (2) interrupting sitting with 6-min light-intensity interval training (LIIT) every 30 min. Investigators will administer the conditions in a counterbalanced order to 54 older adults (40-75 years). Brain function will be assessed using event-related brain potentials and measures of functional connectivity derived from electroencephalography. Cognitive functions will be assessed using a modified Eriksen flanker task and an antisaccade task. Investigators will measure episodic memory using a mnemonic discrimination task.

Inclusion criteria

• Age 40-75 years
• BMI <40 kg/m2
• Sedentary (≥ 6 h/day sitting by a survey question)
• Physically inactive adults based on the CSEP-PATH: Physical Activity and Sedentayr Behaviour Questionnaire (PASB-Q) Adult (low or medium physical activity range equivalent to less than 300 min of moderate intensity physical activity per week)
• Capable of exercising vigorously based on the Physical Activity Readiness Questionnaire (PARQ+)
• Has a medical clearance for maximal exercise and HIIT from a physician
• Normotensive or participant's blood pressure is controlled
• Intelligence quotient (IQ) ≥85
• Fasting plasma glucose <126 mg/dL
• Good or corrected vision and hearing
• Right-handed
• No significant abnormalities on the ECG during the maximal exercise test
• No signs and symptoms that suggest an underlying cardiovascular disease as recorded during the maximal exercise test by a study physician.
• No indications to prematurely stop the maximal exercise test as outlined by the ACSM's Guidelines for Exercise Testing and Prescription
• Concussion if more than 12 months before the study screening.
• History of cancer but in full remission for at least 12 months and no history of chemotherapy, signed off by the physician or an oncologist

Exclusion criteria

• Physical disability or musculoskeletal disease prohibitive to vigorous exercise
• Learning disabilities
• Cognitive impairment (MoCA <26)
• Type 1 or 2 diabetes
• Neurological condition (e.g., Multiple Sclerosis, Parkinson, Dementia, Mild Cognitive Impairment)
• Color blindness
• Brain injury (e.g., traumatic brain injury, stroke, concussion)
• Migraine headaches
• Presence of other health conditions that may be exacerbated by exercise
• History of heart disease
• High cholesterol not controlled by medication
• Signs and symptoms indicative of underlying cardiovascular disease
• A chronic pulmonary disease
• Emphysema
• Pulmonary embolus
• Asthma
• History of renal disease
• History of seizures
• A neuropsychiatric disorder
• Osteoporosis if it interferes with an individual's ability to exercise
• Severe back problems
• Severe arthritis if it interferes with an individual's ability to exercise
• Thyroid disorder not controlled by medication
• Polyneuropathy
• Sleep disorders
• Acquired immunodeficiency syndrome (AIDS)
• Hepatitis C
• History of long Coronavirus Disease 2019 (COVID-19)
• History of cancer if not in full remission for at least 12 months and if a participant had the history of chemotherapy
• Current or past smoking <12 months
• Corticosteroid intake < 31 days before screening
• Opioids taken < 6 months from screening
• Anabolic androgens taken < 31 days before screening
• A serious illness or hospitalization in the last six months
• Currently taking medications that can affect the central nervous system (except for anxiolytics)
• Current participation in an ongoing trial likely to influence exercise ability or cognitive function