Effects of prolonged expiration breathing on cardiopulmonary responses during incremental exercise

This study was designed to clarify the effects of breathing with prolonged expiration on cardiopulmonary responses and autonomic nervous activity during incremental exercise. Eleven healthy men were randomly assigned to breathing mode: a prolonged expiration breathing with a 2-s inspired time and 4-s expired time and a spontaneous breathing without any constraints. Oxygen uptake (V˙O2), ventilation efficiency (V˙E/V˙CO2) and rate pressure product were measured. Low- (LF) and high-frequency (HF) components of blood pressure and heart rate variability were analyzed to assess sympathetic and parasympathetic nervous activities, respectively. V˙E/V˙CO2, rate pressure product and LF were significantly lower, and V˙O2 and HF were significantly higher during exercise with prolonged expiration than with spontaneous breathing. Striking effects of prolonged expiration breathing included the improvement of ventilation efficiency, the suppression of sympathetic nervous activity and the activation of parasympathetic one during incremental exercise. Furthermore, prolonged expiration breathing may have suppressed the exercise-induced increase in myocardial V˙O2.