Examination of controlled frequency breathing under conditions of changing walk cadence

Abstract

The present study was performed to examine controlled frequency breathing (CFB) under conditions of changing walk cadence. Nine healthy male subjects participated in this study. The subjects walked on a treadmill with a cadence of 80 steps/min, and the cadence was changed over 1 min every 4 min to 100, 120, and 140 steps/min. The subjects performed both normal breathing (NB) and CFB with a breathing rate of 20 times/min controlled using a metronome. Respiratory and circulatory responses were compared between CFB and NB. There were no significant differences in heart rate (HR) or minute volume of oxygen uptake (VO_2) suggesting that CFB was equivalent to NB in load. More tidal volume (VT) and fewer respiratory frequency (Rf) were observed in CFB as compared with NB. In NB, minute volume of ventilation (VE) increased by increases in VT and Rf, while VE increased only with VT in CFB. Minute volume of carbon dioxide output (VCO_2), end tidal CO_2 (ETCO_2), VE were lower in CFB as compared with NB. The lower ETCO_2 in CFB led a the gap in partial pressure of carbon dioxide between arterial and venous blood into increase. This improved lactate buffering by bicarbonic acid in active muscle, and a decrease in VCO_2. The lower VCO_2 led to a reduction in VE. In conclusion, CFB could lead to a decrease in VE. This result could be applied to physical therapy in patients with respiratory disease.