Abstract des Autors

The authors investigated whether ultraendurance runners in a 100-km run suffer a decrease of body mass and whether this loss consists of fat mass, skeletal muscle mass, or total body water. Male ultrarunners were measured pre- and postrace to determine body mass, fat mass, and skeletal muscle mass by using the anthropometric method. In addition, bioelectrical impedance analysis was used to determine total body water, and urinary (urinary specific gravity) and hematological parameters (hematocrit and plasma sodium) were measured in order to determine hydration status. Body mass decreased by 1.6 kg (p<.01), fat mass by 0.4 kg (p<.01), and skeletal muscle mass by 0.7 kg (p<.01), whereas total body water increased by 0.8 L (p<.05). Hematocrit and plasma sodium decreased significantly (p<.01), whereas plasma urea and urinary specific gravity (USG) increased significantly (p<.01). The decrease of 2.2 percent body mass and a USG of 1.020 refer to a minimal dehydration. The athletes seem to have been relatively overhydrated (increase in total body water and plasma sodium) and dehydrated (decrease in body mass and increase in USG) during the race, as evidenced by the increased total body water and the fact that plasma sodium and hematocrit were lower postrace than prerace. The change of body mass was associated with the change of total body water (p<.05), and the authors presume the development of edema. Verf.-Referat (geändert)