Exercise Induced Plasma Volume Expansion Lowers Cardiovascular Strain

Study Overview
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Brief Summary
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The goal of this observational study was to better understand the impact of increased plasma volume on later exercise in hypoxia. Investigators examined young, healthy, males who regularly participated in aerobic exercise. Investigators first measured participant's response to exercise in hypoxia (simulated  7,500 feet above sea level). The investigators then had participants either 1) undergo 1 bout of high intensity interval exercise or 2) undergo 1 bout of moderate, continuous exercise. 48 hours after the exercise, participants were again examined in hypoxia.

Detailed Description
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A crossover design was utilized to assess the effects of exercise-induced plasma volume expansion on cycling performance in hypoxia. All participants completed a high intensity (HI) bout and control (CON) intervention in a counterbalanced order. The HI bout consisted of 8x4min cycling bouts at 85% of VO2peak with 4 min rest between intervals. CON consisted of cycling at 50% VO2peak. Two 15 km, self-paced cycling time trials (TT) were performed before and after each training intervention. The first TT occurred 5 days before the training intervention (HI or CON) and the second TT occurred 48 hours post intervention. Interventions were separated by 14 days to ensure sufficient washout of any training effect as data have suggested retention of expanded plasma volume may last for 7-14 days. During washout, participants were instructed to continue their normal exercise routine. The investigators hypothesized that a single HI session would increase plasma volume and attenuate cardiovascular strain during exercise in hypoxia, as evidenced by reductions in HR and elevations in SV and Q. Furthermore, the investigators hypothesized that these changes would contribute to a reduced time-to-completion in a 15 km, self-paced cycling TT.

Official Title
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Exercise Induced Plasma Volume Expansion Lowers Cardiovascular Strain and Improves Cycling Time-trial Performance in Acute Normobaric Hypoxia

Conditions
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Cardiac Output, Stroke Volume

Intervention / Treatment
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* Procedure: High Intensity Intervals
* Procedure: Moderate Exercise


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Males age 18-38 Exercise at least 3 times/week for at least 30 minutes/day for the past 3 months. Exclusion Criteria: Frequent hot bath or sauna users Resided at altitude greater than 2,500 meters for >14 days. Cardiovascular or metabolic disease

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 38 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: High Intensity Exercise<br>Vigorous cycling | Procedure: High Intensity Intervals<br>* 8x4 min cycling bouts at 85% of VO2peak<br>|
| Active Comparator: Continuous Moderate Exercise<br>Leisurely cycling | Procedure: Moderate Exercise<br>* 81 minutes of cycling at 50% VO2peak<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Hemoglobin Concentration | measured through spectroscopy | through study completion, an average of 4 weeks | 
| Hematocrit Concentration | measured through hematocrit reader | through study completion, an average of 4 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Time Trial Time | Time to complete 15 km | through study completion, an average of 4 weeks | 
| Cardiac Output | measured via impedance cardiography | through study completion, an average of 4 weeks | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Hypervolemia, high intensity exercise, altitude exposure