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Changes in body composition in triathletes during an Ironman race

Mueller, Sandro ; Anliker, Elmar ; Knechtle, Patrizia ; Knechtle, Beat ; Toigo, Marco

In: European Journal of Applied Physiology, 2013, vol. 113, no. 9, p. 2343-2352

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    Title
    • Changes in body composition in triathletes during an Ironman race
    Author
    • Mueller, Sandro. Exercise Physiology, Institute of Human Movement Sciences, ETH Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
    • Anliker, Elmar. Exercise Physiology, Institute of Human Movement Sciences, ETH Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
    • Knechtle, Patrizia. Institute of General Practice and Health Services Research, University of Zurich, Zurich, Switzerland
    • Knechtle, Beat. Institute of General Practice and Health Services Research, University of Zurich, Zurich, Switzerland
    • Toigo, Marco. Exercise Physiology, Institute of Human Movement Sciences, ETH Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
    Document Type
    • Postprint
    Language
    • English
    Published in
    • European Journal of Applied Physiology, 2013, vol. 113, no. 9, p. 2343-2352. Springer Berlin Heidelberg
    Other Version
    OAI-PMH Identifier
    • oai:doc.rero.ch:311316
    Summary
    Purpose: Triathletes lose body mass during an Ironman triathlon. However, the associated body composition changes remain enigmatic. Thus, the purpose of this study was to investigate Ironman-induced changes in segmental body composition, using for the first time dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT). Methods: Before and after an Ironman triathlon, segmental body composition and lower leg tissue mass, areas and densities were assessed using DXA and pQCT, respectively, in eight non-professional male triathletes. In addition, blood and urine samples were collected for the determination of hydration status. Results: Body mass decreased by 1.9±0.8kg. This loss was due to 0.4±0.3 and 1.4±0.8kg decrease in fat and lean mass, respectively (P<0.01). Calf muscle density was reduced by 1.93±1.04% (P<0.01). Hemoglobin, hematocrit, and plasma [K+] remained unchanged, while plasma [Na+] (P<0.05), urine specific gravity and plasma and urine osmolality increased (P<0.01). Conclusions: The loss in lean mass was explained by a decrease in muscle density, as an indicator of glycogen loss, and increases in several indicators for dehydration. The measurement of body composition with DXA and pQCT before and after an Ironman triathlon provided exact values for the loss in fat and lean mass. Consequently, these results yielded more detailed insights into tissue catabolism during ultra-endurance exercise