Acute Effects of Coherence Breathing on cardiopulmonary and autonomic responses: a randomized crossover study protocol.

Background. Cardiopulmonary exercise testing (CPET) is a gold-standard test used to evaluate cardiopulmonary fitness and overall health by measuring physiological responses such as oxygen consumption during exercise. While traditional CPET warm-ups are typically low-intensity aerobic activities, alternative methods like coherence breathing may also prepare the body by influencing autonomic regulation. Breathing-based interventions have shown potential to improve heart rate recovery and performance, and heart rate variability (HRV) serves as a useful non-invasive indicator of autonomic nervous system activity. However, there is limited research on how brief breathing exercises before CPET affect outcomes. This study aims to investigate the effects of coherence breathing on oxygen uptake, HRV, and post-exercise heart rate recovery Objective. This study will aim to compare the acute cardiopulmonary and autonomic responses of coherence breathing versus spontaneous breathing immediately preceding cardiopulmonary exercise testing (CPET) in recreationally active healthy adults. Methods. This study will be a randomized counterbalanced crossover design. Healthy adults aged between 19 and 45 years of age will complete two separate CPETs over two non-consecutive test days (between 48 hours and 7days). During each visit, participants will complete five minutes of slow-paced coherence breathing (6 breaths per minute) or spontaneous breathing at normal breathing rate, followed by an incremental treadmill CPET protocol up to maximal exertion. HRV will be assessed at baseline, during the breathing interventions, and during cool-down for 5 minutes using the Emwave Pro Plus software. Gas exchange during the CPET protocol will be measured continuously using the VO2 Master Pro system. immediately after, and after 5 minutes of resting. The primary outcomes will be peak oxygen consumption and heart rate variability indices. Secondary outcomes will include heart rate recovery, peak heart rate, time to exhaustion, rate of perceived exertion and readiness, blood pressure, tidal volume, peak ventilation, and respiration rate. Analyses will use linear mixed-effects models and paired comparisons. Discussion. This protocol will determine whether pre-exercise coherence breathing can improve cardiopulmonary and autonomic nervous system responses to maximal performance. Findings may have practical implications for exercise testing and performance procedures as well as improving our understanding of pre-exercise breathing strategies for priming the autonomic and cardiopulmonary systems.