Ventilation and gas exchange on-kinetics during rest to work transition inresponse to pedal frequency

The purpose of these experiments was to determine the effects of different pedal rates, at a constant power output, on the kinetics of expired ventila tion (V-E), oxygen uptake (VO2) and carbon dioxide output (VCO2) during the transition from rest to exercise. Six healthy male volunteers underwent si x submaximal constant-load cycle tests at approximately 85% of the ventilat ory threshold. The tests consisted of three trials each at 30 and 100 revol utions per minute (rpm), the order being counterbalanced and the data avera ged over the three trials for each treatment. V-E, VO2 and VCO2 were monito red every 15 s for 6 min. Ventilation and gas exchange were measured using a computerized open-circuit technique and the data fit by a non-linear Gaus s-Newton regression using a single exponential model incorporating a time d elay. Despite the constant power output during both treatments, steady-stat e values for all variables were significantly higher (P < 0.05) at 100 rpm (V-E = 21.2%; VO2 = 12.6%; VCO2 = 15.2%; HR = 7.4%). Kinetic analysis of VO 2 revealed no significant difference in the mean response time (MRT) betwee n treatments. In contrast, the MRT for VCO2 and V-E were greater (P < 0.05) for the 30 rpm trial (VCO2 = 15%; V-E = 15.4%). These data suggest that hi gher rate of muscle contraction decreases the MRT of both VCO2 and V-E in t he transition from rest to work. However, VO2 on-kinetics were not altered by pedal frequency at these submaximal levels. Med Sci Res 27:379-383 (C) 1 999 Lippincott Williams & Wilkins.