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

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_W') may require refinement to enable effective use in an elite population.

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_CP). Using the framework of the SKIBA 2 model, the τ_W' values were modified for each protocol to achieve an accurate W' at volitional exhaustion. Modified τ_W' values were compared with equivalent SKIBA 2 τ_W' values to assess the difference in recovery rates for this population. Plotting modified τ_W' values against D_CP showed the adjusted relationship between work rate and recovery rate.

Comparing modified τ_W' values against the SKIBA 2 τ_W' 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_W'-D_CP relationship was best described by a power function: τ_W' = 2287.2 × D_CP^-0.688 (R² = .433).

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