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.
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 Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
SINGLE
Enrollment
15
Inspired gas content
USARIEM
Natick, Massachusetts, United States
2 mile self-paced treadmill time trial performance
Time to complete self-paced 2 mile treadmill time trial (min:sec)
Time frame: 30 minutes
Ventilation rate
Ventilation rate will be assessed using a pneumotachometer \[L/min\]
Time frame: 30 minutes
Oxygen consumption
Oxygen consumption will be assessed using computerized indirect calorimetry \[ml/kg/min\]
Time frame: 30 minutes
Heart rate
Heart rate will be assessed using telemetry \[beats per min\]
Time frame: 30 minutes
Arterialized capillary pH
Arterialized capillary pH will be assessed using a blood gas analyzer \[Unitless\]
Time frame: 30 minutes
Arterialized capillary pCO2
Arterialized capillary pCO2 will be assessed using a blood gas analyzer \[mmHg\]
Time frame: 30 minutes
Arterialized capillary HCO3
Arterialized capillary HCO3 will be assessed using a blood gas analyzer \[mEq/L\]
Time frame: 30 minutes
Rating of perceived exertion
Rating of perceived exertion will be assessed using Borg's 6-20 scale \[AU\]
Time frame: 30 minutes
This platform is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional.
Dyspnea
Rating of perceived dyspnea will be assessed using Borg's 0-10 scale \[AU\]
Time frame: 30 minutes
Leg discomfort
Rating of perceived leg discomfort will be assessed using Borg's 0-10 scale \[AU\]
Time frame: 30 minutes
Headache
Headache will be assessed using a visual analog scale \[AU\]
Time frame: 30 minutes
Breathing descriptors
Breathing descriptors will be assessed by having participants check statements that apply to their breathing (e.g., breathing out requires more effort) \[unitless\]
Time frame: 30 minutes