Accuracy of W' Recovery Kinetics in High Performance Cyclists-Modeling Intermittent Work Capacity.

Purpose: With knowledge of an individual's critical power and W', the SKIBA 2 model provides a framework with which to track W' balance during intermittent high-intensity work bouts. There are fears that the time constant controlling the recovery rate of W' (τ) may require refinement to enable effective use in an elite population.

Methods: Four elite endurance cyclists completed an array of intermittent exercise protocols to volitional exhaustion. Each protocol lasted approximately 3.5-6 min and featured a range of recovery intensities, set in relation to the athlete's critical power (D). Using the framework of the SKIBA 2 model, the τ values were modified for each protocol to achieve an accurate W' at volitional exhaustion. Modified τ values were compared with equivalent SKIBA 2 τ values to assess the difference in recovery rates for this population. Plotting modified τ values against D showed the adjusted relationship between work rate and recovery rate.

Results: Comparing modified τ values against the SKIBA 2 τ values showed a negative bias of 112 (46) s (mean ± 95% confidence limits), suggesting that athletes recovered W' faster than predicted by SKIBA 2 (P = .0001). The modified τ-D relationship was best described by a power function: τ = 2287.2 × D (R = .433).

Conclusions: The current SKIBA 2 model is not appropriate for use in elite cyclists, as it underpredicts the recovery rate of W'. The modified τ equation presented will require validation but appears more appropriate for high-performance athletes. Individual τ relationships may be necessary to maximize the model's validity.