Durability of the moderate-to-heavy intensity transition can be predicted using readily available markers of physiological decoupling.

PURPOSE

To assess relationships between heart rate (HR), ventilation (̇ ), and respiratory frequency (F) decoupling and durability of the first ventilatory threshold (VT), and the strength of practical models to predict power output at VT during prolonged exercise.

METHODS

Durability of VT was assessed via measurements of power output at VT before and after ~ 2.5-h of initially moderate-intensity cycling in 51 trained cyclists, as part of four studies published elsewhere. In 12 of those participants, power output at VT was assessed every hour until task failure. For every assessment of power output at VT, HR, F, and ̇ was measured at fixed power outputs, and thus decoupling of these variables with power output was determined. Bivariate repeated-measures correlations (r) between decoupling and durability of VT were assessed. Multivariable models were created to predict power output at VT during prolonged exercise using generalised estimating equations.

RESULTS

Negative correlations were observed between exercise-induced change in power output at VT and HR (r = -0.76, P < 0.001) and F (r = -0.40, P = 0.013) decoupling, but not ̇ decoupling (r = -0.25, P = 0.136). The final prediction model, containing baseline VT and peak oxygen uptake, F decoupling, and an interaction between HR decoupling and exercise duration, effectively predicted real-time VT (mean absolute error, ~ 7.2 W; R, 0.95).

CONCLUSION

HR and/or F decoupling during controlled training sessions may be a practically useful durability assessment. Our prediction models may be an effective means of improving within-session intensity regulation and training load monitoring.