Introduction: Wim-Hof breathing (WHB) combines periods of hyperventilation (HV) followed by voluntary breath holding (BH) at low lung volumes until one can hold it. It is increasingly used by recreational and professional athletes to improve physical performance. Purpose: We compared the acute metabolic, cardiovascular, and respiratory response to the maximal aerobic capacity test (MACT) after WHB with the response to the MAPT after spontaneous breathing. Methods: Fourteen healthy recreational athletes participated in our crossover study. After baseline measurements, the MAPT was performed with a randomly selected breathing pattern applied immediately prior to exercise: spontaneous breathing (control) or WHB. For WHB, participants followed the breathing instructions of the mobile application of the WHB method: HV (30 deep breaths), BH, and deep inhalation held for 15 seconds, repeated three times. The Cosmed Quark PFT system was used to measure various cardiac, respiratory, and metabolic parameters before and during MAPT: heart rate, end-tidal partial pressure of carbon dioxide and oxygen (PetCO2 and PetO2), oxygen consumption (V ̇O2), carbon dioxide production (V ̇CO2), pulmonary ventilation (VE), workload and derived parameters such as the ratio of V ̇O2 to workload before reaching the anaerobic threshold (V ̇O2/WR slope), ventilatory equivalents, oxygen pulse. Participants rated their perception of exertion (RPE) during MAPT. ANOVA for repeated measures was performed and p < 0.05 was considered evident for significant differences between the two trials. Results: Analysis showed positive effects of WHB practice prior to MAPT on V ̇O2/WR slope and RPE. We found lower V ̇O2/WR slope during WHB trial compared to control (p = 0.016) and lower RPE after WHB compared to control (p = 0.015). Discussion and Conclusion: Our results suggest that athletes may benefit from performing WHB pre- exercise as less physical exertion is perceived compared to no WHB. A lower V ̇O2/WR slope after WHB may be either a positive or negative adaptation to WHB: it may represent better oxygen uptake efficiency or lower oxygen availability in active muscles. A limitation of our study was the small number of participants. In physical therapy, WHB could be a key strategy to keep patients with cardiovascular and respiratory diseases who usually stop physical activity due to the great RPE. Therefore, we would like to extend the study to patients with cardiovascular and respiratory diseases.
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