Factors That Influence Blood Vessel Regulation During Exercise in Humans

Overview

This study will examine two separate interventions: 1) the effects of ischemic preconditioning or 2) a high fat meal on the capacity of the brachial artery to overcome sympathetic activation and dilate during exercise (also known as functional sympatholysis). Participants will be asked to complete rhythmic handgrip exercise with and without the application of -20 mmHg lower body negative pressure to increase sympathetic activation. Doppler ultrasound will be used to continuously measure brachial artery blood flow. Participants will complete the handgrip exercise and lower body negative pressure before and after the applications of each interventions. Participants may elect to only complete one intervention rather than complete both protocols. Intervention one is active or control ischemic preconditioning. Intervention two is high or low fat meals.

Study Type

  • Study Type: Interventional
  • Study Design
    • Allocation: Randomized
    • Intervention Model: Crossover Assignment
    • Primary Purpose: Basic Science
    • Masking: None (Open Label)
  • Study Primary Completion Date: November 15, 2022

Interventions

  • Procedure: Ischemic preconditioning
    • Four 5-minute cycles of 200 mmHg cuff inflation of the brachial artery, each separated by 5-minutes deflated recovery (i.e. 40 minutes total time)
  • Procedure: Ischemic preconditioning control
    • Four 5-minute cycles of 20 mmHg cuff inflation of the brachial artery, each separated by 5-minutes deflated recovery (i.e. 40 minutes total time)
  • Dietary Supplement: Low fat meal
    • Meal containing 1006 calories, 1 g fat, 0.2 g saturated fat, 0 g trans fat, 20 mg cholesterol, 191 g carbohydrates, 60 g protein, 1560 mg sodium
  • Dietary Supplement: High fat meal
    • Meal containing 1030 calories, 62 g fat, 23 g saturated fat, 0.5 g trans fat, 445 mg cholesterol, 76 g carbohydrates, 41 g protein, 2080 mg sodium.

Arms, Groups and Cohorts

  • Sham Comparator: Ischemic preconditioning control
  • Active Comparator: Ischemic preconditioning
  • Active Comparator: High fat meal
  • Placebo Comparator: Low fat meal

Clinical Trial Outcome Measures

Primary Measures

  • Forearm blood flow
    • Time Frame: Baseline – Immediately before active and control interventions
    • Doppler ultrasound – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Forearm blood flow
    • Time Frame: Immediately after active and control interventions (IPC only)
    • Doppler ultrasound – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Forearm blood flow
    • Time Frame: 1 hour after active and control interventions (Diet intervention only)
    • Doppler ultrasound – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Forearm blood flow
    • Time Frame: 2 hours after active and control interventions (Diet intervention only)
    • Doppler ultrasound – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Forearm blood flow
    • Time Frame: 3 hours after active and control interventions (Diet intervention only)
    • Doppler ultrasound – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Forearm vascular conductance
    • Time Frame: Baseline – Immediately before active and control interventions
    • Blood flow divided by blood pressure – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Forearm vascular conductance
    • Time Frame: Immediately after active and control interventions (IPC only)
    • Blood flow divided by blood pressure – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Forearm vascular conductance
    • Time Frame: 1 hour after active and control interventions (Diet intervention only)
    • Blood flow divided by blood pressure – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Forearm vascular conductance
    • Time Frame: 2 hours after active and control interventions (Diet intervention only)
    • Blood flow divided by blood pressure – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Forearm vascular conductance
    • Time Frame: 3 hours after active and control interventions (Diet intervention only)
    • Blood flow divided by blood pressure – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure

Secondary Measures

  • Blood pressure
    • Time Frame: Baseline – Immediately before active and control interventions
    • Finger plethysmography – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Blood pressure
    • Time Frame: Immediately after active and control interventions (IPC only)
    • Finger plethysmography – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Blood pressure
    • Time Frame: 1 hour after active and control interventions (Diet intervention only)
    • Finger plethysmography – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Blood pressure
    • Time Frame: 2 hours after active and control interventions (Diet intervention only)
    • Finger plethysmography – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Blood pressure
    • Time Frame: 3 hours after active and control interventions (Diet intervention only)
    • Finger plethysmography – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Heart rate
    • Time Frame: Baseline – Immediately before active and control interventions
    • ECG – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Heart rate
    • Time Frame: Immediately after active and control interventions (IPC only)
    • ECG – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Heart rate
    • Time Frame: 1 hour after active and control interventions (Diet intervention only)
    • ECG – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Heart rate
    • Time Frame: 2 hours after active and control interventions (Diet intervention only)
    • ECG – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure
  • Heart rate
    • Time Frame: 3 hours after active and control interventions (Diet intervention only)
    • ECG – tested at rest and during rhythmic handgrip exercise with and without lower body negative pressure

Participating in This Clinical Trial

Inclusion Criteria

  • 18 years or older – Healthy Exclusion Criteria:

  • History of smoking (tobacco or cannabis), defined as any smoking within the past 3 months – Diagnosed cardiovascular or metabolic disease(s) – Recent musculoskeletal injury handgrip exercise – Prescription of chronic medications other than oral contraceptives – History of hypertension or presence of arrhythmia

Gender Eligibility: All

Minimum Age: 18 Years

Maximum Age: 50 Years

Are Healthy Volunteers Accepted: Accepts Healthy Volunteers

Investigator Details

  • Lead Sponsor
    • University of Guelph
  • Provider of Information About this Clinical Study
    • Principal Investigator: Philip Millar, Associate Professor – University of Guelph

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