The purpose of the study was to investigate the influence of training with reduced breathing frequency (RBF) on tidal volume during incremental exercise where breathing frequency was restricted and on ventilatory response during exercise when breathing a 3% CO₂ mixture. Twelve male participants were divided into two groups: experimental (Group E) and control (Group C). Both groups participated three cycle ergometry interval training sessions per week for six weeks. Group E performed it with RBF i.e. 10 breaths per minute and group C with spontaneous breathing. After training Group E showed a higher vital capacity (+8 ± 8%; p = 0.02) and lower ventilatory response during exercise when breathing a 3% CO₂ mixture (-45 ± 27%; p = 0.03) compared with pre-training. These parameters were unchanged in Group C. Post-training peak power output with RBF (PPO_RBF) was increased in both groups. The improvement was greater in Group E (+42 ± 11%; p < 0.01) than in Group C (+11 ± 9%; p = 0.03). Tidal volume at PPO_RBF was higher post-training in Group E (+41 ± 19%; p = 0.01). The results of the present study indicate that RBF training during cycle ergometry exercise increased tidal volume during incremental exercise where breathing frequency was restricted and decreased ventilatory sensitivity during exercise when breathing a 3% CO₂ mixture.

• Training with a reduced breathing frequency during exercise decreased ventilator sensitivity to carbon dioxide. In addition, it increased minute ventilation during exercise with imposed reduced breathing frequency.

• Training with reduced breathing frequency could not be realized at higher intensity of exercise due to the additional stress caused by such a breathing pattern. Therefore the improvement in aerobic endurance (considering peak oxygen uptake) could not be expected after this kind of training.