Purpose: To compare the ventilatory response of two incremental exercise tests and determine their predictive validity on 40-km cycle time trial (40K) mean power output (40Kavgwatts). Methods: Fifteen male cyclists performed two incremental exercise tests (T50x3:100 W +50 W[middle dot]3 min-1, T25x1:20 W + 25 W[middle dot]min-1) and a 40K over an 8-d period. Key variable was power at ventilatory threshold (VT). For VT determination during each test we used: [latin capital V with dot above]E/[latin capital V with dot above]O2 method, first clear breakpoint on the [latin capital V with dot above]E/[latin capital V with dot above]CO2 plot, V-slope method, RER = 1, and RER = 0.95. Results: [latin capital V with dot above]O2max during T50x3 and T25x1 was not different (66.6 vs 67.6 mL[middle dot]kg-1[middle dot]min-1), although T25x1 peak power output (MaxT25x1; 402 W) was significantly higher than MaxT50x3 (363 W). T50x3 and T25x1 VT power outputs indicated that the power output at T25x1:RER = 1 and T25x1:RER = 0.95 were significantly higher compared with T50x3 (324 vs 304 W and 282 vs 264 W, respectively). Regression analyses between T50x3 variables and 40Kavgwatts were significant for T50x3:V-slope (R2 = 0.37; SEE 20.2 W), T50x3:[latin capital V with dot above]E/[latin capital V with dot above]O2 (R2 = 0.64; SEE 15.3 W), T50x3:RER = 0.95 (R2 = 0.42; SEE 19.4 W), T50x3:RER = 1 (R2 = 0.45; SEE 18.8 W), and MaxT50x3 (R2 = 0.51; SEE 17.8 W). Regression analyses between T25x1 variables and 40Kavgwatts were significant for T25x1:V-slope (R2 = 0.63; SEE 15.4 W), T25x1:[latin capital V with dot above]E/[latin capital V with dot above]O2 (R2 = 0.64; SEE 15.2 W), T25x1:RER = 0.95 (R2 = 0.53; SEE 17.4 W), T25x1:RER = 1 (R2 = 0.57; SEE 16.7 W), and MaxT25x1 (R2 = 0.65; SEE 15.0 W). There was no significant difference between 40Kavgwatts (282 W) and power outputs at T50x3:[latin capital V with dot above]E/[latin capital V with dot above]O2 (277 W), T50x3:V-slope (289 W), T25x1:[latin capital V with dot above]E/[latin capital V with dot above]O2 (276 W), and T25x1:RER = 0.95 (282 W). Conclusion: Generally, T25x1 based VT variables were superior to T50x3 variables regarding the prediction of 40Kavgwatts. We conclude that the [latin capital V with dot above]E/[latin capital V with dot above]O2 method is protocol independent and a valid 40Kavgwatts predictor.
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