The 3-minute all-out exercise test (3MT) has emerged as a useful procedure for identifying critical power (CP) and the finite work capacity above CP (W') within a single visit. The CP concept enables for the prediction of exhaustive time limits (T(LIMs)) for a wide range of severe intensity power outputs and is a method for prescribing high-intensity interval training (HIIT). Road cyclists often use the CompuTrainer for indoor HIIT. The purpose of this study was to validate the 3MT for use on the CompuTrainer. On 4 separate visits, 10 competitive cyclists performed a 3MT, and three separate constant-load bouts projected to yield exhaustive T(LIMs) of 3, 6, and 9 minutes, respectively, using the Computrainer. Actual CP and W' were calculated using the linear work-time (W-t) and power-inverse time (1/t) models. The results for CP (W) from the 3MT (215 ± 40), the W-t model (212 ± 36), and the 1/t model (213 ± 36) did not differ (F = 2.96, p = 0.11, η2(p) = 0.43). Similarly, the results for W' (kJ) for the 3MT (11.2 ± 4.0), the W-t model (12.1 ± 6.5), and the 1/s model (11.7 ± 6.3) did not differ (F = 2.40, p = 0.15, η2(p) = 0.375). We conclude that use of the 3MT and the CP concept for performance assessment and HIIT prescription on the CompuTrainer is a valid procedure.