Abstract des Autors

The purpose of this investigation was to compare the ventilatory threshold (Tvent) with the lactate threshold (Tlact) during 60 min of steady-state exercise at the calculated thresholds. Eight trained, male cyclists (mean age 23.3+/-3.0 years, body mass 70.0+/-7.1 kg, VO2max 61.02+/-4.15 ml/kg/min) performed a progressive intensity cycling test (23 W/min) for determining Tlact and Tvent. Tvent was determined by the non-linear increase in excess CO2 (ExCO2) while Tlact was calculated by the "individual anaerobic threshold" (IAT) method. Subsequently, subjects performed an up to 60 min steady-state exercise at the threshold workloads the results at Tlact being significantly higher from those at Tvent at P<0.01 in VO2, ExCO2, HR, blood lactate concentration (BLa) and workload, as calculated by Hotelling's T**2-test. During the steady state exercise at each specified workload, VO2, BLa, heart rate and ExCO2 were measured at 15 min intervals. All subjects completed the steady-state exercise at Tvent (VSS) while the steady-state exercise at Tlact (LSS) - only 2 subjects (mean time 48.4 min). Comparison of metabolic variables using MANOVA and multiple comparisons revealed significant differences between VSS and LSS for HR and VO2 at all time intervals, for BLa at 30 and 45 min intervals and for ExCO2 at the 30 min interval. Furthermore, examination of BLa over time using trend analysis revealed a stabilization during VSS (3.05 mmol/l) whereas BLa continuously increased over time during LSS. Our findings indicate that Tlact (IAT method) overestimates the ability to perform prolonged work over 45 min while Tvent (ExCO2) allows for steady-state exercise longer than 60 min. Verf.-Referat