Metabolic profile of the Ironman World Championships: A case study

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Purpose: The purpose of this study was to determine the metabolic profile during the 2006 Ironman World Championship in Kailua-Kona, Hawaii. Methods: One recreational male triathlete completed the race in10:40:16. Before the race, linear regression models were established from both laboratory and field measures to estimate energy expenditure and substrate utilization. The subject was provided with an oral dose of 2H218O approximately 64 h before the race to calculate total energy expenditure (TEE) and water turnover with the doubly labeled water (DLW) technique. Body weight, blood sodium and hematocrit, and muscle glycogen (via muscle biopsy) were analyzed pre- and postrace. Results: The TEE from DLW and indirect calorimetry was similar: 37.3 MJ (8,926 kcal) and 37.8 MJ (9,029 kcal), respectively. Total body water turnover was16.6 L, and body weight decreased 5.9 kg. Hematocrit increased from 46 to 51% PCV. Muscle glycogen decreased from152 to 48 mmoL/kg wet weight pre- to postrace. Conclusion: These data demonstrate the unique physiological demands of the Ironman World Championship and should be considered by athletes and coaches to prepare sufficient nutritional and hydration plans.

Original languageEnglish
Pages (from-to)570-576
Number of pages7
JournalInternational Journal of Sports Physiology and Performance
Issue number4
StatePublished - Dec 2010


  • Doubly labeled water
  • Hydration
  • Muscle glycogen
  • Ultra-endurance
  • Water turnover


Dive into the research topics of 'Metabolic profile of the Ironman World Championships: A case study'. Together they form a unique fingerprint.

Cite this