Combined Effects of Prolonged Sitting and Mental Stress on the Cardiovascular System
Condition: Sedentary Behavior; Cardiovascular Risk Factor; Mental Stress; Cognitive Change; Cerebrovascular Insufficiency
MeSH terms: Cerebrovascular Disorders; Stress, Psychological
Study type: Interventional

Summary: 
      Prolonged sitting may pose a public health risk through its effects on the cardiovascular
      system, and may lead to impaired whole-body cardiovascular health, which includes both
      vascular and cerebrovascular function. These effects may interact with other environmental
      variables, such as stress. However, no study has investigated the combined effect of a mental
      stressor and prolonged sitting on vascular and cerebrovascular function. The combined effect
      of prolonged sitting and mental stress may lead to an exacerbated effect on vascular,
      cerebrovascular, and executive function. The investigators hypothesize that mental stress
      with the addition of prolonged sitting [PS] will result in a greater increase in peripheral,
      central and cerebral arterial stiffness and elicit a decrease in cerebral perfusion, total
      blood flow to the brain, middle cerebral artery velocity and executive function, compared to
      mental stress without prolonged sitting [CON]. The findings from this study may result in a
      public health message regarding sedentary behavior and stress, and will help elucidate the
      mechanisms behind acute vascular, cerebrovascular, and cognitive dysfunction during prolonged
      sitting.
    

Detailed description: 
      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.
    

Intervention name(s): Mental Arithmetic Test
Intervention type(s): Behavioral
Intervention description(s): The researcher will call out a four-digit number and ask the participant to subtract either 7 or 13. Each minute, a new four-digit number will be called out and the participant must subtract the 7 or 13 from the number. The test will last approximately 5 minutes
Other intervention name(s): Mental Stressor
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Participants will be exposed to mental stress following either 20 min or 120 min sitting
Masking: None (Open Label)
Primary purpose: Prevention