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.