Liapaki, PinelopiSoultanakis , HelenKalomenidis, IoannisClemente Suárez, Vicente JavierMourtakos, StamatisZakynthinos, SpyrosClemente Suárez, Vicente Javier2025-09-202025-09-202025Liapaki, P., Soultanakis, H., Kalomenidis, I., Clemente-Suárez, V. J., Mourtakos, S., Zakynthinos, S. (2025). Effects of Apnoea versus Normal Breathing on Physiological Responses during High-Intensity Interval Training in Swimming. Journal of Human Kinetics, 99. https://doi.org/10.5114/jhk/195587https://hdl.handle.net/11268/16144The objective of this research was to examine the impact of conventional breathing versus apnoea technique on acid-base equilibrium, physiological reactions, and performance throughout high-intensity interval training sessions in swimming. Two groups of sixteen athletes completed 6 x 50-m intervals of freestyle swimming with normal breathing and apnoea at maximum intensity, with a 1-min rest interval. Capillary blood gasses (pH, PCO2, PO2, HCO3, Hct, Hb) were collected at four measurement time points: 1) at rest, 2) at rest just after the 3rd repetition, 3) at finish, and 4) at the 10th min of recovery. Measured variables included the heart rate (HR) during swimming, lactate (La) concentration and swimming time (t50). Uncompensated metabolic acidosis, exhibiting greater prominence during apnoea, was attributed to heightened lactic acidosis under both breathing conditions. Despite experiencing bradycardia, swimmers demonstrated faster completion times during apnoea. In conclusion, during repeated high-intensity short-distance swimming, specifically 50 m of freestyle, apnoea enhances sprint performance without compensating for metabolic acidosis.engAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/journal article10.5114/jhk/195587open accessDeporteNataciónFisiología humanaGoal 3: Ensure healthy lives and promote well-being for all at all ages