This randomized crossover trial will examine the acute effects of pre-exercise coherence breathing on cardiopulmonary exercise responses in recreationally active adults. Participants will complete two experimental conditions in randomized order: 5 minutes of guided coherence breathing and 5 minutes of quiet seated spontaneous breathing. Following each condition, participants will perform a standardized treadmill warm-up and a maximal cardiopulmonary exercise test. Outcomes will include oxygen consumption, heart rate, heart rate recovery, perceived exertion, time to completion, and heart rate variability. The findings may help determine whether coherence breathing can serve as an effective autonomic priming strategy before a bout of maximal exercise

Slow-paced breathing performed at approximately six breaths per minute has been shown to influence autonomic nervous system activity and heart rate variability. Coherence breathing may improve physiological regulation by enhancing cardiorespiratory synchronization and vagal modulation. However, little is known about whether a brief bout of coherence breathing performed immediately before exercise can influence cardiopulmonary exercise performance. The purpose of this study is to investigate the acute effects of pre-exercise coherence breathing on cardiopulmonary exercise performance and autonomic responses in recreationally active adults. This study will utilize a randomized, counterbalanced crossover design. Recreationally active adults aged 19 to 45 years will complete two experimental conditions in random order separated by a minimum of 48 hours (maximum of 7 days). In one condition, participants will perform 5 minutes of guided coherence breathing using a visual breathing pacer at approximately 6 breaths per minute while seated. In the comparison condition, participants will sit quietly for 5 minutes with spontaneous breathing. Following each condition, participants will complete a standardized treadmill warm-up and a maximal cardiopulmonary exercise test (CPET). Heart rate variability will be assessed during baseline seated rest and during the breathing intervention. Cardiopulmonary variables collected during CPET will include oxygen consumption, heart rate, respiratory responses, and ratings of perceived exertion. Recovery responses over 5 minutes seated include heart rate and blood pressure will also be assessed following exercise.

Findings from this study may improve our understanding of breathing strategies for athletic performance. Specifically, whether slow paced breathing through coherence breathing can serve as a practical autonomic priming strategy before maximal exercise. Moreover, insights from this study may provide insight into the acute interaction between breathing regulation, autonomic function, and exercise responses.

Inclusion Criteria:

• Adults aged 19 to 45 years.
• Any biological sex.
• Recreationally active, defined as accumulating at least 3 hours per week of moderate-to-vigorous physical activity.
• Able to perform maximal cardiopulmonary exercise testing on a treadmill.
• Able to provide informed consent.
• Cleared for moderate-to-vigorous physical activity based on the PAR-Q+ (or PAR-Q 2023).

Exclusion Criteria:

• Accumulate less than 3 hours per week of moderate-to-vigorous physical activity.
• Presence of a health condition that contraindicates maximal exercise testing, including:

Cardiovascular disease. Pulmonary disease. Metabolic disorders. Neuromuscular disorders. Orthopedic limitations that impair exercise performance.

• Acute illness that would interfere with participation or exercise testing.
• Inability or unwillingness to complete study procedures.
• Inability or unwillingness to provide informed consent.
• Not cleared for moderate-to-vigorous physical activity based on the PAR-Q+ (or PAR-Q+ 2023).