The purpose of this study was to determine the specific metabolic and neuromuscular responses at critical power (CP) from the 3-min all-out test. Nine men (mean ± SD: aged 23.7 ± 3.3 years) performed an incremental test for the determination of peak oxygen consumption (VO(2peak)) and gas exchange threshold. CP was estimated for each subject from the 3-min all-out test. Oxygen consumption (VO(2)), the ventilation versus carbon dioxide production ratio (V(E)/VCO(2) ratio), electromyographic (EMG) amplitude, and EMG mean power frequency (MPF) were examined during exhaustive rides at CP for each subject. There was no significant difference between the VO(2) at exhaustion (40.6 ± 7.5 mL·kg(-1)·min(-1)) and VO(2peak) (42.9 ± 7.3 mL·kg(-1)·min(-1)). Furthermore, there were significant increases in EMG amplitude and the V(E)/VCO(2) ratio during the exhaustive rides at CP. There was, however, no significant change in EMG MPF over time. Therefore, the current findings indicated that the 3-min all-out test overestimated CP and the demarcation between the heavy- and severe-intensity domains. Specifically, the VO(2), ventilatory, and EMG amplitude responses were consistent with those observed during continuous exercise in the severe exercise intensity domain. It is likely that the ventilatory and EMG amplitude responses were associated with a common mechanism of fatigue that is different from what affects EMG MPF.