Abstract

To examine the fatigue response during an exhaustive heavy exercise performed under control of oxygen uptake (SS@VO2Δ50) or power output (SS@pΔ50), eleven trained male subjects performed an incremental test to determine the peak of the oxygen uptake value (VO2peak) and lactate threshold and two exhaustive steady-state cycling exercises at the intermediate value between the lactate threshold and VO2peak (SS@VO2Δ50 and SS@pΔ50). The control of VO2 induced an oscillation of the power output, which lowered the average power output (276 ± 47 vs. 315 ± 40 W, p = 0.004) and cancelled the slow component of oxygen kinetics. However, all subjects reached maximal cardiac output (CO) and heart rate (HR) values which were sustained almost two times longer in SS@VO2Δ50 compared to SS@pΔ50 (979 ± 854 vs. 475 ± 236 s, p = 0.046 for CO and 1050 ± 890 vs. 513 ± 288 s, p = 0.037 for HR). Furthermore, SS@pΔ50 elicited VO2peak but not SS@VO2Δ50 (4963 ± 434 vs. 4723 ± 460 mL•min-1, p = 0.026). Finally, the time spent at the maximal CO and HR values is correlated with time to exhaustion at VO2Δ50. In conclusion, the cause of fatigue does not seem to have the same origin during exhaustive supra-lactate threshold exercise under control of VO2 (VO2Δ50) compared to constant power output (pΔ50), while both elicit the maximal HR and CO values. Verf.-Referat