Energy Expenditure during Extreme Endurance Exercise: The Giro d’Italia

Purpose Little data are available on doubly labeled water (DLW) assessed total daily energy expenditure (TDEE) during extreme endurance exercise. DLW is considered the gold standard to measure TDEE, but different calculations are being used, which may have a large impact on the results. The aim of the current study was to measure TDEE during the Giro d'Italia and apply two different calculation methods. Methods Seven male cyclists (age 28 ± 5 y, BMI 22.1 ± 2.1 kg/m2) completed the 24-days professional cycling race 'Giro d'Italia' in which a total distance of 3445 km was covered, including 10 mountain stages. TDEE was measured over the entire duration of the race, with the ingestion of DLW at three different time points. To calculate TDEE and body composition, the isotope dilution space was calculated using two different techniques, the 'plateau' and 'intercept' technique. Results The %fat mass at baseline was 7.8% and 16.8% with the plateau and intercept technique respectively and did not significantly change over the course of the race. TDEE was on average 32.3 ± 3.4 MJ/day using the plateau technique versus 28.9 ± 3.2 using the intercept technique, resulting in an average physical activity level (PAL) of 4.37 ± 0.43 versus 3.91±0.39, respectively. The dilution space ratio was on average 1.030 with the plateau and 1.060 with the intercept technique. Conclusion Given that the observed dilution space ratio with the plateau technique is similar as the expected ratio from literature and the % fat mass of 7.8% is more realistic for the athletes being studied, we propose the application of the plateau rather than the intercept method, when using DLW during extreme endurance exercise. Address for correspondence: Guy Plasqui, Department of Human Biology, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands. Tel. + 31 43 3881506. Fax. + 31 43 3670976. E-mail G.Plasqui@maastrichtuniversity.nl The authors have no conflicts of interest to declare. No external funding was obtained for the current study. The results of the present study do not constitute endorsement by ACSM. The authors declare that the results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for publication: October 2018. © 2018 American College of Sports Medicine

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