Influence of Graded Hypercapnia on Endurance Exercise Performance
Study Details
Study Description
Brief Summary
The aim of this randomized, single-blind, placebo-controlled crossover trial is to determine the effects of graded hypercapnia (0, 2, and 4% inspired CO2) on endurance performance. Twelve healthy and fit young adults (men and women) will complete this study. Participants will perform experimental trials on 3 separate days (one each breathing 0%, 2%, and 4% inspired CO2-all with normal 21% oxygen). During each trial, they will perform 10 minutes of submaximal treadmill walking exercise and then complete a self-paced 2-mile treadmill run time-trial.
| Condition or Disease | Intervention/Treatment | Phase |
|---|---|---|
|
N/A |
Detailed Description
Participants will undergo baseline measurements of pulmonary function and maximal oxygen uptake (VO2max). They will then complete two familiarization trials, with 10 minutes of submaximal exercise (~40%VO2max) followed by a self-paced 2-mile treadmill time trial. Lastly, they will complete three experimental trials, repeating the same submaximal and time-trial exercise procedures while breathing the test gas (0%, 2%, or 4% CO2-all with normal 21% oxygen). During the experimental trials, arterialized capillary blood samples will be collected at rest breathing room air, at rest breathing the test gas, and during submaximal exercise at 40% VO2max breathing the test gas. The primary outcome is 2-mile treadmill time-trial performance. Secondary outcomes include ventilation, metabolic rate, heart rate, arterialized capillary pH/PCO2/HCO3, perceived exertion, dyspnea, leg discomfort, breathing descriptors, and headache ratings.
Study Design
Arms and Interventions
| Arm | Intervention/Treatment |
|---|---|
| Experimental: 4% CO2 Inspired gas containing 4% CO2, 21% O2, balance N2 |
Other: Inspired gas
Inspired gas content
|
| Experimental: 2% CO2 Inspired gas containing 2% CO2, 21% O2, balance N2 |
Other: Inspired gas
Inspired gas content
|
| Sham Comparator: 0% CO2 Inspired gas containing 0% CO2, 21% O2, balance N2 |
Other: Inspired gas
Inspired gas content
|
Outcome Measures
Primary Outcome Measures
- 2 mile self-paced treadmill time trial performance [30 minutes]
Time to complete self-paced 2 mile treadmill time trial (min:sec)
Secondary Outcome Measures
- Ventilation rate [30 minutes]
Ventilation rate will be assessed using a pneumotachometer [L/min]
- Oxygen consumption [30 minutes]
Oxygen consumption will be assessed using computerized indirect calorimetry [ml/kg/min]
- Heart rate [30 minutes]
Heart rate will be assessed using telemetry [beats per min]
- Arterialized capillary pH [30 minutes]
Arterialized capillary pH will be assessed using a blood gas analyzer [Unitless]
- Arterialized capillary pCO2 [30 minutes]
Arterialized capillary pCO2 will be assessed using a blood gas analyzer [mmHg]
- Arterialized capillary HCO3 [30 minutes]
Arterialized capillary HCO3 will be assessed using a blood gas analyzer [mEq/L]
- Rating of perceived exertion [30 minutes]
Rating of perceived exertion will be assessed using Borg's 6-20 scale [AU]
- Dyspnea [30 minutes]
Rating of perceived dyspnea will be assessed using Borg's 0-10 scale [AU]
- Leg discomfort [30 minutes]
Rating of perceived leg discomfort will be assessed using Borg's 0-10 scale [AU]
- Headache [30 minutes]
Headache will be assessed using a visual analog scale [AU]
- Breathing descriptors [30 minutes]
Breathing descriptors will be assessed by having participants check statements that apply to their breathing (e.g., breathing out requires more effort) [unitless]
Eligibility Criteria
Criteria
Inclusion Criteria:
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Male or female, age 18-45
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In good health as determined by medical screening
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Passed his/her most recent Army Combat Fitness Test (ACFT) (Military Volunteers Only) or performs aerobic exercise at least 2 times per week and able to complete two mile run in ≤ 21 minutes (Civilian Volunteers)
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Willing to not participate in any exercise or drink alcoholic beverages for 24 hours before each study visit.
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Willing to not take part in any strenuous exercise in the 36 hours before each visit.
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Willing not to drink caffeine or eat food until after testing on familiarization and performance testing visits (visits 2-6).
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Willing to maintain a similar dietary pattern in the 2 days before each familiarization and performance visits.
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Have supervisor approval if permanent party military or a federal employee at U.S. Army Natick Soldier System Center
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Able to speak and read English fluently
Exclusion Criteria:
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Females who are pregnant or planning to become pregnant during the study
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Taking dietary supplements, prescriptions, or over the counter medication, other than a contraceptive (unless approved by medical staff & PI)
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Musculoskeletal injuries that compromise ability to run on a treadmill
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Abnormal blood count, presence of abnormal blood chemicals (hemoglobin S or sickle cell traits)
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Smokers or tobacco/nicotine users (unless have quit > 1 month prior)
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Any history of asthma
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Current or recent respiratory tract or sinus infections (< 1 month prior)
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Allergy to skin adhesive
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Any history of migraine or recurrent headaches
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Any history of panic disorder
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Blood donation in the previous 8 weeks
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Positive Covid-19 test within the last month
Contacts and Locations
Locations
| Site | City | State | Country | Postal Code | |
|---|---|---|---|---|---|
| 1 | USARIEM | Natick | Massachusetts | United States | 01760 |
Sponsors and Collaborators
- United States Army Research Institute of Environmental Medicine
Investigators
- Principal Investigator: Benjamin J Ryan, Ph.D., United States Army Research Institute of Environmental Medicine
Study Documents (Full-Text)
More Information
Publications
None provided.- USARIEM