Exercise Physiology, Institute of Human Movement Sciences, ETH Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
Eur J Appl Physiol. 2013 Sep;113(9):2343-52. doi: 10.1007/s00421-013-2670-3. Epub 2013 Jun 9.
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).
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.
Body mass decreased by 1.9 ± 0.8 kg. This loss was due to 0.4 ± 0.3 and 1.4 ± 0.8 kg 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).
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.
铁人三项运动员在完成铁人三项比赛时会失去体重。然而，相关的身体成分变化仍然难以解释。因此，本研究的目的是使用双能 X 射线吸收法（DXA）和外周定量计算机断层扫描（pQCT）首次研究铁人三项引起的身体成分的变化。
在铁人三项比赛前后，分别使用 DXA 和 pQCT 评估 8 名非专业男性铁人三项运动员的身体成分。此外，还采集血液和尿液样本以确定水合状态。
体重减轻了 1.9 ± 0.8 公斤。这种损失是由于脂肪和瘦体重分别减少了 0.4 ± 0.3 和 1.4 ± 0.8 公斤（P < 0.01）。小腿肌肉密度降低了 1.93 ± 1.04%（P < 0.01）。血红蛋白、红细胞压积和血浆 [K(+)] 保持不变，而血浆 [Na(+)]（P < 0.05）、尿比重以及血浆和尿液渗透压升高（P < 0.01）。
瘦体重的减少是由于肌肉密度的降低，作为糖原损失的指标，以及几种脱水指标的增加。铁人三项比赛前后使用 DXA 和 pQCT 测量身体成分提供了脂肪和瘦体重损失的准确值。因此，这些结果更详细地了解了超耐力运动期间的组织分解代谢。
