Comparison of inter-trial recovery times for the determination of critical power and W' in cycling

Critical Power (CP) and W' are often determined using multi-day testing protocols. To investigate this cumbersome testing method, the purpose of this study was to compare the differences between the conventional use of a 24-h inter-trial recovery time with those of 3h and 30min for the determination of CP and W'. Methods: 9 moderately trained cyclists performed an incremental test to exhaustion to establish the power output associated with the maximum oxygen uptake (p(max)), and 3 protocols requiring time-to-exhaustion trials at a constant work-rate performed at 80%, 100% and 105% of p(max.) Design: Protocol A utilised 24-h inter-trial recovery (CP24/W'(24)), protocol B utilised 3-h inter-trial recovery (CP3/W'(3)), and protocol C used 30-min inter-trial recovery period (CP0.5/W'(0.5)). CP and W' were calculated using the inverse time (1/t) versus power (P) relation (P=W'(1/t) + CP). Results: 95% Limits of Agreement between protocol A and B were -9 to 15W; -7.4 to 7.8kJ (CP/W') and between protocol A and protocol C they were -27 to 22W; -7.2 to 15.1kJ (CP/W'). Compared to criterion protocol A, the average prediction error of protocol B was 2.5% (CP) and 25.6% (W'), whilst for protocol C it was 3.7% (CP) and 32.9% (W'). Conclusion: 3-h and 30-min inter-trial recovery time protocols provide valid methods of determining CP but not W' in cycling.