Influence of Graded Hypercapnia on Endurance Exercise Performance
- Conditions
- Hypercapnia
- Interventions
- Other: Inspired gas
- Registration Number
- NCT05116397
- Lead Sponsor
- United States Army Research Institute of Environmental Medicine
- 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.
- 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.
Recruitment & Eligibility
- Status
- COMPLETED
- Sex
- All
- Target Recruitment
- 15
- Male or female, age 18-45
- In good health as determined by medical screening
- 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)
- Willing to not participate in any exercise or drink alcoholic beverages for 24 hours before each study visit.
- Willing to not take part in any strenuous exercise in the 36 hours before each visit.
- Willing not to drink caffeine or eat food until after testing on familiarization and performance testing visits (visits 2-6).
- Willing to maintain a similar dietary pattern in the 2 days before each familiarization and performance visits.
- Have supervisor approval if permanent party military or a federal employee at U.S. Army Natick Soldier System Center
- Able to speak and read English fluently
- Females who are pregnant or planning to become pregnant during the study
- Taking dietary supplements, prescriptions, or over the counter medication, other than a contraceptive (unless approved by medical staff & PI)
- Musculoskeletal injuries that compromise ability to run on a treadmill
- Abnormal blood count, presence of abnormal blood chemicals (hemoglobin S or sickle cell traits)
- Smokers or tobacco/nicotine users (unless have quit > 1 month prior)
- Any history of asthma
- Current or recent respiratory tract or sinus infections (< 1 month prior)
- Allergy to skin adhesive
- Any history of migraine or recurrent headaches
- Any history of panic disorder
- Blood donation in the previous 8 weeks
- Positive Covid-19 test within the last month
Study & Design
- Study Type
- INTERVENTIONAL
- Study Design
- CROSSOVER
- Arm && Interventions
Group Intervention Description 2% CO2 Inspired gas Inspired gas containing 2% CO2, 21% O2, balance N2 4% CO2 Inspired gas Inspired gas containing 4% CO2, 21% O2, balance N2 0% CO2 Inspired gas Inspired gas containing 0% CO2, 21% O2, balance N2
- Primary Outcome Measures
Name Time Method 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
Name Time Method 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 \[mmHg\]
Rating of perceived exertion 30 minutes Rating of perceived exertion will be assessed using Borg's 6-20 scale \[AU\]
Ventilation rate 30 minutes Ventilation rate will be assessed using a pneumotachometer \[L/min\]
Dyspnea 30 minutes Rating of perceived dyspnea 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) \[unitless\]
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 HCO3 30 minutes Arterialized capillary HCO3 will be assessed using a blood gas analyzer \[mEq/L\]
Leg discomfort 30 minutes Rating of perceived leg discomfort will be assessed using Borg's 0-10 scale \[AU\]
Trial Locations
- Locations (1)
USARIEM
🇺🇸Natick, Massachusetts, United States