Validity and reliability of critical power field testing

Purpose: To test the validity and reliability of field critical power (CP). Method: Laboratory CP tests comprised three exhaustive trials at intensities of 80, 100 and 105 % maximal aerobic power and CP results were compared with those determined from the field. Experiment 1: cyclists performed three CP field tests which comprised maximal efforts of 12, 7 and 3 min with a 30 min recovery between efforts. Experiment 2: cyclists performed 3 × 3, 3 × 7 and 3 × 12 min individual maximal efforts in a randomised order in the field. Experiment 3: the highest 3, 7 and 12 min power outputs were extracted from field training and racing data. Results: Standard error of the estimate of CP was 4.5, 5.8 and 5.2 % for experiments 1–3, respectively. Limits of agreement for CP were −26 to 29, 26 to 53 and −34 to 44 W for experiments 1–3, respectively. Mean coefficient of variation in field CP was 2.4, 6.5 and 3.5 % for experiments 1–3, respectively. Intraclass correlation coefficients of the three repeated trials for CP were 0.99, 0.96 and 0.99 for experiments 1–3, respectively. Conclusions: Results suggest field-testing using the different protocols from this research study, produce both valid and reliable CP values.