Factors That Influence Blood Vessel Regulation During Exercise in Humans

Overview

This study will examine the effects of ischemic preconditioning or 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. Near infrared spectroscopy will assess forearm oxygenation and deoxygenation. Participants will complete the handgrip exercise and lower body negative pressure before and after the applications of two interventions. 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: April 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: High fat meal
    • Meal containing 1000 calories, 6 g fat, 1.5 g saturated fat, 0 g trans fat, 0 mg cholesterol, 187 g carbohydrates, 47 g protein, 450 mg sodium
  • Dietary Supplement: Low fat meal
    • Meal containing 1030 calories, 60 g fat, 23 g saturated fat, 0.5 g trans fat, 450 mg cholesterol, 79 g carbohydrates, 41 g protein, 2,050 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
  • Forearm blood flow
    • Time Frame: 30 minutes after active and control interventions
    • Doppler ultrasound
  • Forearm vascular conductance
    • Time Frame: Baseline – Immediately before active and control interventions
    • Blood flow divided by blood pressure
  • Forearm vascular conductance
    • Time Frame: 30 minutes after active and control interventions
    • Blood flow divided by blood pressure

Secondary Measures

  • Oxygenated hemoglobin
    • Time Frame: Baseline – Immediately before active and control interventions
    • Near infrared spectroscopy
  • Oxygenated hemoglobin
    • Time Frame: 30 minutes after active and control interventions
    • Near infrared spectroscopy
  • Deoxygenated hemoglobin
    • Time Frame: Baseline – Immediately before active and control interventions
    • Near infrared spectroscopy
  • Deoxygenated hemoglobin
    • Time Frame: 30 minutes after active and control interventions
    • Near infrared spectroscopy
  • Tissue saturation index
    • Time Frame: Baseline – Immediately before active and control interventions
    • Near infrared spectroscopy
  • Tissue saturation index
    • Time Frame: 30 minutes after active and control interventions
    • Near infrared spectroscopy
  • Blood pressure
    • Time Frame: Baseline – Immediately before active and control interventions
    • Finger plethysmography
  • Blood pressure
    • Time Frame: 30 minutes after active and control interventions
    • Finger plethysmography
  • Heart rate
    • Time Frame: Baseline – Immediately before active and control interventions
    • ECG
  • Heart rate
    • Time Frame: 30 minutes after active and control interventions
    • ECG

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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