Abstract des Autors

This study investigated the effect of 10 W/min (Slow ramp, SR), 30 W/min (Medium ramp, MR) and 50 W/min (Fast ramp, FR) exercise protocols on assessments of the first (VT1) and second (VT2) ventilation thresholds and peak oxygen uptake (VO2peak) in 12 highly-trained male cyclists (mean ± SD age = 26 ± 6 yr). Expired gas sampled from a mixing chamber was analyzed online and VT1 and VT2 were defined as two break-points in 20-s-average plots of pulmonary ventilation (VE), ventilatory equivalents for O2 (VE/VO2) and CO2 (VE/VCO2), and fractions of expired O2 (FEO2) and CO2 (FECO2). Arterialized-venous blood samples were analyzed for blood-gas and acid-base status. VO2peak was significantly lower (p<0.05) for SR (4.65 ± 0.53 l/min) compared to MR (4.89 ± 0.56 l/min) and FR (4.88 ± 0.57 l/min) protocols. CO2 output and blood PCO2 were lower (p<0.05), and VE/VCO2 was higher (p<0.05), above VT1 for SR compared to MR and FR protocols. No significant differences were observed among the protocols for VO2, % VO2peak, VE, plasma lactate ([La-]) and blood hydrogen ion concentration ([H+]), and heart rate (HR) values at VT1 or VT2. The work rate (WR) measured at VT1, VT2 and VO2peak increased (p<0.05) with steeper ramp slopes. It was concluded that, in highly-trained cyclists, assessments of VT1 and VT2 are independent of ramp rate (10, 30, 50 W/min) when expressed as VO2, % VO2peak, VE, plasma [La-], blood [H+] and HR values, whereas VO2peak is lower during 10 W/min compared to 30 and 50 W/min ramp protocols. In addition, the WR measured at VT1, VT2 and VO2peak varies with the ramp slope and should be utilized cautiously when prescribing training or evaluating performance. Verf.-Referat