The purpose of this study is to clarify the effects of different ventilatory rate, which was 1:1 or 1:2 ventilation/pedal ratio with a 1:1 inspiratory/expiratory ratio, on dyspnea and ventilatory parameters under the constant pedal exercise with a bicycle ergometer.
Twenty-one healthy young individuals (age: 19.7±0.6 y, male=13) were included in the study.
Participants were asked to pedal a bicycle ergometer at 50 beats/min and a ventilation threshold intensity for 20 minutes while wearing an exhaled gas analyzer (AE-100i; MINATO MEDICAL SCIENCE Co., ltd. JP) mask. The conditions were (1) 25 breaths/min (inhale/exhale at a half cycle respectively; 25BPM) and (2) 50 breaths/min (inhale/exhale at a single cycle respectively; 50BPM), and the participants were instructed to synchronize a pedal and breathing. The rest period between the two conditions was at least one hour.
The indices measured were subjective exercise intensity of dyspnea and leg fatigue (RPE_D, RPE_L), minute oxygen uptake (VO2), ratio of dead space to tidal volume (VD/VT), and minute ventilation/carbon dioxide output ratio (VE/VCO2), at 10 and 20 minutes after the start of exercise.
The indices were compared between conditions by t-test or Wilcoxon test at a significance level of 5%.
RPE_L in the 50BPM condition was significantly higher than that in the 25BPM condition only at 20 minutes (p=0.004). VO2 was not different between conditions at 10 and 20 minutes. Both of VD/VT and VE/VCO2 in the 50BPM condition were higher than that in the 25BPM condition at both 10 and 20 minutes (all p0.001).
The higher VE/VCO2 in the 50BPM condition suggests that, in general, exercise was easier in the 50BPM than in the 25BPM condition. However, this is not consistent with the fact that RPE_L was higher in the 50BPM condition after 20 minutes; VO2 comparisons showed no differences between conditions, and VD/VT was lower in the 50BPM condition, suggesting that the 50BPM condition was addressed by a decrease in VT. Participants commented that it was difficult to match ventilation to a pedal in the 50BPM condition, suggesting that the psychological burden associated with ventilation/pedal adjustments may have contributed to the fatigue of the exercise.
The results suggest that, in healthy individuals, the 25BPM condition is sufficient ventilation to obtain an oxygen uptake, which was needed for exercise at a ventilatory threshold intensity.
ventilatory rates
dyspnea
