INTRODUCTION: Accurate determination of total daily energy expenditure (TDEE) in professional cyclists is important to inform on appropriate energy intake, which in turn is required for optimal performance and injury prevention [1]. Current approaches of determining TDEE are however insufficiently accurate as they typically use basal metabolic rate (BMR) prediction equations that are developed for non-elite athletes in combination with a generic physical activity level (PAL) value to determine non-exercise energy expenditure (EE). This is combined with exercise energy expenditure (EEE) estimated from power data to determine TDEE. Knowledge about the non-exercise PAL-value and BMR equations for professional cyclists would improve the accuracy of this approach, but are currently unavailable. We therefore aimed to 1) determine the non-exercise PAL-value during training and competition based on power data in combination with a measured BMR and doubly-labelled water (DLW), and 2) compare outcomes between a multi-day cycling competition (Vuelta a España) and single-day races (Ardennes classics). METHODS: Twenty-one male professional cyclists participated. The following parameters were measured: 1) BMR, 2) the relation between power output and EE during an incremental cycling test, 3) TDEE using DLW. The relation between power output and EE was used to determine EE during exercise (EEE). A non-exercise PAL value was obtained by subtracting BMR and EEE from TDEE. We compared the measured BMR to BMR predicted with popular equations and compared TDEE estimated with a generic approach to our approach. RESULTS: Measured BMR was 7.9 ± 0.8 MJ/day, which was significantly higher than predicted by the Oxford equations (6.95 ± 0.5 MJ/day), but not different from the Ten Haaf [2] equation (7.87 ± 0.46 MJ/day). Mean TDEE was 31.8 ± 2.6 MJ/day and 27.3 ± 2.8 MJ/day, EEE was 21.1 ± 1.9 MJ/day and 27.8 ± 3.4 MJ/day (for only the race days), and the non-exercise PAL was 1.3 and 1.8 for the Vuelta and Ardennes classics, respectively. Non-exercise EE was estimated to be 11.51 MJ/day with the ten Haaf [2] BMR equation and a generic PAL-value of 1.45 for sedentary or light activity lifestyle [3], which overestimated non-exercise EE by 0.88 MJ/day (~3%) as compared to the measured BMR and PAL-value of 1.3 for the Vuelta. CONCLUSION: The proposed approach can be used to get more accurate estimations of TDEE than the use of a generic PAL value in combination with BMR predictive equations developed for non-elite athletes, and is also relatively easy to implement in practice. This in turn can improve nutritional strategies in professional cyclists. A secondary finding is that TDEE is higher, while EEE and the non-exercise PAL are lower in a multi-day cycling competition compared to single-day races.
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