Purpose W' balance (W'BAL) modelling is becoming an important tool to monitor intermittent cycling performance. This study assessed the ability of different time constant (tW') 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. Methods Thirteen cyclists performed cycling performance tests to determine: lactate threshold (LT), critical power (CP), W', VO2max, maximal aerobic power (MAP) and maximal sprint power (Pmax). Participants subsequently performed three intermittent W' 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, 20:10TE; repeated 20 s intervals each separated by 10 s recoveries. W'BAL was determined via five different tW' equations and an individualised equation (tW'INDV) calculated from the 20:10TE under the assumption that the point of task failure represents 0 kJ. Results Current tW' equations failed to predict exhaustion during intermittent exercise protocols to exhaustion. Total work done above CP for the 20:10TE (W'total20:10TE) was positively correlated with absolute and relative LT, CP, VO2max, MAP, and Pmax (r = 0.64-0.80; P < 0.05). The tW'INDV was negatively correlated with relative CP (r = - 0.69), and LT1 (r = - 0.58), and W'total20:10TE (r = - 0.63). Conclusion Individualised tW' should be utilised for the accurate prediction of W'BAL. W'rec is influenced primarily by aerobic performance parameters, including LT1 and CP.
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