Combined Effects of Prolonged Sitting and Mental Stress on the Cardiovascular System

This study is a multi-visit (three in total) randomized crossover trial. During a single familiarization session, the research team will obtain informed consent, and will describe to participants the purposes and procedures of this study. They will then be exposed to all experimental devices on in a quiet, dimly lit and environmentally controlled room. Participants will return to the same location for two experimental conditions following these pre-assessment guidelines:

• Fasted (> 12 hours), consuming only water.
• No caffeine consumption 12 hours prior to testing.
• No vigorous exercise 24 hours prior to testing.
• No alcohol consumption 24 hours prior to testing.

Participants will arrive to the Applied Physiology Laboratory between 6:00 and 10:00 a.m. fasted (for Visit 3: 2-5 days following the Visit 2). Participants will be fasted and refrain from caffeine intake for at least 12 hours, and alcohol and strenuous physical activity for at least 24 hours prior to arrival. Upon arrival, height and weight will be recorded followed by 10 minutes of quiet rest in the supine position. During these 10 minutes, the subject will be fitted with a Near Infra-Red Spectroscopy probe on the prefrontal cortex and medial gastrocnemius. The non-invasive continuous blood pressure, transcranial doppler, and Vicorder arterial stiffness devices will also be affixed to the participant during this time period during this time. Sitting periods will begin for both conditions once all devices are attached to the participant, the subject is shifted to an upright seated position, and at least 10 minutes of supine rest has been recorded. During the control (CON) visit, subjects will undergo a brief 20 minute sitting period. For the prolonged sitting (PS) condition, subjects will be asked to sit still and quietly for 2 hours while watching a non-stimulating documentary. Each condition will receive the mental stress at the conclusion of the sitting periods in both CON and PS. After exposure to the mental stress in both conditions, data collection procedures for this protocol will be completed. Arterial stiffness measurements will be made immediately after the mental stress, and then every 5 minutes, up to 30 minutes. Brain blood flow will be assessed by ultrasound after completion of the arterial stiffness measures. Finally, a battery of cognitive tests (Verbal Fluency Test and Trails A+B tests) will be administered to the participant.

Inclusion criteria

• Healthy male or female

Exclusion criteria

• Any known cardio-metabolic disorders
• Taking medications known to affect cardiovascular function
• Report drug or alcohol abuse
• Report cigarette smoking
• Pregnant women