W′ reconstitution modelling during intermittent exercise performed to task failure

<h4><b>Purpose</b></h4><p dir="ltr">W′ balance (W′BAL) modelling is becoming an important tool to monitor intermittent cycling performance. This study assessed the ability of different time constant (τ_W′) equations for W′ reconstitution (W′_rec) to predict exhaustion during intermittent exercise and the relationship between parameters of W′_rec with established determinants of endurance performance.</p><h4><b>Methods</b></h4><p dir="ltr">Thirteen cyclists performed cycling performance tests to determine: lactate threshold (LT), critical power (CP), W′, V̇O_2max, maximal aerobic power (MAP) and maximal sprint power (P_max). Participants subsequently performed three intermittent Wʹ depletion trials to volitional exhaustion involving different work and recovery periods: 20:10; 3 × 20 s intervals separated by 10 s recoveries before a final continuous effort, 60:30; 3 × 60 s intervals separated by 30 s recoveries before a final continuous effort, 20:10_TE; repeated 20 s intervals each separated by 10 s recoveries. W′_BAL was determined via five different τ_W′ equations and an individualised equation (τ_W′INDV) calculated from the 20:10_TE under the assumption that the point of task failure represents 0 kJ.</p><h4><b>Results</b></h4><p dir="ltr">Current τ_W′ equations failed to predict exhaustion during intermittent exercise protocols to exhaustion. Total work done above CP for the 20:10TE (Wʹ_total20:10_TE) was positively correlated with absolute and relative LT, CP, V̇O_2max, MAP, and P_max (r = 0.64–0.80; P < 0.05). The τ_W′INDV was negatively correlated with relative CP (r = − 0.69), and LT1 (r = − 0.58), and Wʹ_total20:10_TE (r = − 0.63).</p><h4><b>Conclusion</b></h4><p dir="ltr">Individualised τ_W′ should be utilised for the accurate prediction of Wʹ_BAL. W′_rec is influenced primarily by aerobic performance parameters, including LT₁ and CP.</p>