Effects of Apnoea versus Normal Breathing on Physiological Responses during High-Intensity Interval Training in Swimming

The 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 3^rd repetition, 3) at finish, and 4) at the 10^th 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.