This study investigates whether respiratory muscle training (RMT) and dietary nitrate supplementation can improve exercise tolerance under simulated moderate altitude conditions. Exposure to reduced oxygen availability at altitude places additional strain on the cardiovascular and respiratory systems, which may limit endurance performance. By combining RMT-designed to strengthen the muscles involved in breathing-with nitrate therapy, which enhances nitric oxide availability and vascular function, this study aims to determine whether these interventions independently or synergistically improve oxygen delivery, reduce physiological strain, and enhance exercise performance. The findings will help identify non-pharmacological strategies to improve physical performance and tolerance to hypoxia in both clinical and operational environments.
This study is designed to test whether two non-drug interventions-respiratory muscle training (RMT) and dietary nitrate supplementation-can improve exercise performance and tolerance when oxygen levels are lower than normal, such as at moderate altitude. When people exercise in low-oxygen environments, the body must work harder to deliver enough oxygen to the muscles. This can lead to faster fatigue and reduced endurance. Strengthening the breathing muscles and improving blood vessel function may help the body adapt better to these conditions. This study will explore how RMT and nitrate supplementation, either alone or together, affect breathing, blood flow, and exercise capacity. Why This Study Is Being Done: Researchers want to find out whether strengthening the breathing muscles through RMT, and increasing nitric oxide in the body through nitrate (found naturally in beetroot juice), can make it easier to exercise when oxygen is limited. Nitric oxide helps widen blood vessels and improve oxygen delivery to muscles. The goal is to learn if these approaches can help healthy adults perform better in low-oxygen conditions and whether combining them produces a greater benefit than using either one alone. Who Will Participate: Healthy, recreationally active adults will take part in this study. Participants will not have any known heart, lung, or metabolic disease. They will be randomly assigned to one of four groups: Breathing training plus nitrate supplement Breathing training plus placebo Sham (fake) breathing training plus nitrate supplement Sham (fake) breathing training plus placebo What Participants Will Do: Each participant will complete testing before and after a 4- to 6-week intervention period. During the intervention: Participants in the RMT group will use a handheld breathing trainer several times per week to strengthen their breathing muscles. Participants in the nitrate group will drink a small amount of concentrated beetroot juice daily. Those in the sham groups will use a very low-resistance breathing device or a placebo drink that looks and tastes the same but contains no nitrate. Before and after training, participants will perform exercise tests on a stationary bicycle both at normal oxygen levels and at simulated altitude inside a controlled environmental chamber. Testing will measure: How long participants can exercise before becoming fatigued. Oxygen use (VO₂), heart rate, breathing, and blood pressure during exercise. Breathing muscle strength and endurance. Oxygen levels in the blood and muscles. Study Goals and Measurements: Researchers will compare how exercise performance and physiological responses change with each treatment. The main goal is to see whether RMT and nitrate supplementation increase exercise tolerance at simulated altitude. Secondary goals include understanding how these interventions affect breathing patterns, oxygen use efficiency, and cardiovascular function during exercise. Why This Study Matters: This research will help scientists and health professionals understand how to improve physical performance and resilience when oxygen is limited. The findings could be useful for: Pilots, military personnel, and athletes who train or work at altitude. Patients with conditions that make breathing or exercise difficult, such as heart or lung disease. Future spaceflight or aerospace medicine applications, where oxygen availability can vary. Safety and Ethics: All participants will give written informed consent before joining the study. The study has been reviewed and approved by the Institutional Review Board for the Protection of Human Subjects in Research at Embry-Riddle Aeronautical University. All research procedures will follow the ethical principles outlined in the Declaration of Helsinki. Expected Impact: The results will show whether combining breathing training with nitrate supplementation can serve as a simple, non-pharmacological strategy to improve tolerance to low-oxygen environments. This could lead to better performance strategies for athletes, aviators, and others who face hypoxic or high-altitude conditions, as well as inform clinical approaches for patients who struggle with exercise intolerance.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
QUADRUPLE
Enrollment
80
Participants perform supervised respiratory muscle training (RMT) using a handheld resistive breathing device designed to strengthen the inspiratory and expiratory muscles. Training sessions are conducted 5 days per week for approximately 4-6 weeks. Each session includes a series of resisted breathing maneuvers with progressively increased load as tolerated. The device is calibrated to maintain a constant pressure threshold to ensure consistent training intensity.
Participants use an identical handheld breathing device with minimal resistance, providing no meaningful training stimulus. The training schedule and session duration match those of the active RMT group to maintain participant blinding.
Participants consume a standardized dose of concentrated beetroot juice daily for the duration of the training period (approximately 4-6 weeks). The supplement provides a fixed quantity of dietary nitrate known to enhance nitric oxide availability and support vascular and metabolic function during exercise.
Participants consume a placebo beverage identical in color, taste, and appearance to the nitrate supplement but containing no active nitrate. The beverage is consumed daily following the same schedule as the active supplement.
Embry-Riddle Aeronautical University
Daytona Beach, Florida, United States
RECRUITINGChange in Exercise Tolerance at Simulated Altitude
Exercise tolerance will be measured as the time to exhaustion during a graded cycling exercise test performed under simulated moderate altitude conditions (\~2,500-3,000 meters). Tests will be conducted before and after the 4-6 week intervention period. The measure reflects overall improvements in aerobic performance and fatigue resistance following respiratory muscle training, nitrate supplementation, or their combination.
Time frame: Baseline to Post-Intervention (approximately 4-6 weeks)
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