Author(s): LIU, Y., BLACK, M.I., JONES, A.M., Institution: UNIVERSITY OF EXETER, Country: UNITED KINGDOM, Abstract-ID: 863

INTRODUCTION:
W' balance (W'BAL) models estimate dynamic changes in work capacity (W') above critical power (CP), accounting for linear depletion and curvilinear recovery during high-intensity intermittent exercise. However, current models using generalized time constants (tau) inadequately account for prior W' utilization and differences in W' reconstitution between passive and active recovery across depletion states. This study aimed to compare the performance of integral convolution equation (W'BAL-INT) and ordinary differential equation (W'BAL-ODE) models using tau derived from all-out effort tests involving different depletion states and recovery modes (i.e., passive versus active recovery) when applied to exhaustive intermittent exercise with active recovery. We hypothesized that active recovery-based tau would improve model performance.
METHODS:
15 recreationally active adults (male/females: 10/5; age: 29 +/- 7 years; body mass, 72.9 +/- 8.5 kg; height 1.74 +/- 0.08 m) completed an initial ramp test and four further tests, involving a 3-min all-out test (3MT) paired with a 1-min sprint performed either before or after the 3MT. CP and W' were derived from fresh condition 3MT. The two sprint segments were separated by either 60 s of active recovery at 80% gas exchange threshold (GET) or complete rest. Subsequently, the participants completed an intermittent exercise session consisting of ten 1-min self-paced work bouts interspersed with 1-min recovery at 80% GET, with the instruction to reach volitional exhaustion by the 10th bout. Recovery tau was derived from the test through an iterative process and used to estimate W'BAL during intermittent sessions, assuming W' = 0 at volitional exhaustion.
RESULTS:
There was a significant difference between adjusted model variations (F = 27.09, p < 0.001, eta_p^2 = 0.66). The individualized, test-derived tau did not improve exhaustion prediction accuracy for the novel W'BAL-INT and W'BAL-ODE model permutations compared with the standard W'BAL-INT (F = 39.31, p < 0.001, eta_p^2 = 0.74) and W'BAL-ODE permutations (F = 5.76, p < 0.001, eta_p^2 = 0.29). During intermittent exercise, test-based W'BAL-INT permutations overestimated the W' reconstitution (p < 0.001), whereas test-based W'BAL-ODE permutations underestimated the W' reconstitution (p < 0.05). A significant negative correlation was found between the W'BAL-ODE test-derived tau and the magnitude of observed W' reconstitution (r = -0.66, p < 0.001), with larger tau values associated with lower W' recovery between all-out effort bouts. There was no correlation between CP and observed W' reconstitution (p = 0.47).
CONCLUSION:
Recovery tau derived from all-out effort tests do not improve W'BAL prediction accuracy for intermittent exercise. These findings indicate that W' reconstitution behaviour differs between short-duration, fast-depletion efforts and intermittent exercise, suggesting limited transferability of recovery parameters between fast-depletion and intermittent exercise contexts.