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Article Excerpt
We 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% body mass and a USG of 1.020 refer to a minimal dehydration. Our 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 preface. The change of body mass was associated with the change of total body water (p < .05), and we presume the development of
Key words: body composition, percent body fat, skinfold thickness, ultraendurance
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F at is the main energy-rich substrate in an ultraendurance performance (Helge et al., 2003; Raschka & Plath, 1992). As a consequence, long-distance performances lead to a decrease of body mass due to the decrease of fat mass. A decrease of body mass is generally observed during different ultraendurance performances, such as ultrarunning (Skenderi, Kavouras, Anastasiou, Yiannakouris, & Matalas, 2006), ultracycling (Neumayr et al., 2003; Neumayr et al., 2005), and ultratriathlon (Gastmann et al., 1998; Lehmann, Huonker, & Dimeo, 1995).
The decrease of body mass is mainly a consequence of reduced fat mass (Helge et al., 2003; Raschka & Plath, 1992; Raschka et al., 1991), but in some studies (Bircher, Enggist, Jehle, & Knechtle, 2006; Knechtle, Enggist, & Jehle, 2005) a decrease of skeletal muscle mass (Knechtle & Kohler, 2007; Knechtle, Duff, Amtmann, & Kohler, 2008) or lean body mass (Helge et al.) during ultraendurance performances was documented. In some of the described performances (Knechtle & Bircher, 2005; Knechtle & Kohler), the eccentric running led to damage of the skeletal muscle and consequently to a decrease of skeletal muscle mass.
In one case study (Knechtle & Bircher, 2005), and, up to now, in only one field study of a multistage ultraendurance run (Knechtle & Kohler, 2007), a significant decrease of skeletal muscle mass was described in ultraendurance running. In the study by Helge et al. (2003), 4 participants crossed the Greenland icecap on cross country skis, and lean body mass was reduced. However, cross-country skiing is not comparable to running, and lean body mass is not identical to skeletal muscle mass. Due to the fact that only an anthropometric method was used in the above-mentioned studies (Knechtle & Bircher; Knechtle & Kohler), we wanted to investigate whether a decrease of skeletal muscle mass can be documented during an ultraendurance run. Therefore we examined a larger sample of ultraendurance runners, in a 100-km run, to determine whether they would suffer a degradation of adipose subcutaneous tissue, or whether they would experience a loss of skeletal muscle mass. In addition, we aimed to quantify both the loss of fat mass and the loss of skeletal muscle mass.
Method
Participants
The organizer of the 49th edition of the 100-km run in Biel, Switzerland, contacted all participants of the race in 2007 by a separate newsletter, 3 months before the race, in which they were asked to participate in the study. About 1,000 male runners started in the race, and 41 male nonprofessional Caucasian ultrarunners were interested in our investigation. They all gave their informed written consent in accordance with the guidelines established by the Institutional Ethics Committee of the Canton St. Gallen, Switzerland. No criteria for inclusion or exclusion were used. Thirty-nine athletes (M age = 44.2 years, SD = 12.3; M body mass = 74.1 kg, SD = 9.8; M height = 1.77 m, SD = 0.07; and M body mass index = 23.5 kg/[m.sup.2], SD = 2.2) in our study group finished the race within the time limit, and one runner finished in the top three. Two runners of our study group had to give up the race due to medical problems. Our athletes were experienced ultrarunners. During their training they ran, on average, 7.4 hr (SD = 2.7) and covered 76.6 km (SD = 31.5) per week. Thirty-six runners had already finished 28.8 (SD = 56.4) marathons before this race, and 25 athletes had already finished 8.5 (SD = 12.6) 100-km runs. Their average personal best times in the marathon and in the 100-km run, respectively, were 206 min (SD = 30) and 686 min (SD = 141).
The Race
The 100-km run took place June 15-16, 2007. The runners started at 10:00 p.m. on June 15 to run 100 km with a change in altitude of 645 m. During this run, they passed 17 aid stations with food and beverages. The athletes were allowed to be supported by a cyclist in order to have additional food and clothing, if necessary. At the start, the temperature was 20[degrees]C, and it was dry. During the night, the temperature dropped to 12[degrees]C, and from 2:00 a.m. to 3:00 a.m., heavy rain fell.
Measurements and Calculations
Before the start of the race (from 5:00 p.m. to 10:00 p.m.) and immediately after arrival at the finish line, every participant underwent anthropometric measurements, bioelectrical impedance analysis (BIA) and the collection of capillary blood and urinary samples in order to determine body mass (BM), skeletal muscle mass (SM), percent body fat (%BF), and percent total body water (%TBW). Samples of urine were collected for determination of urinary specific gravity (USG) in order to quantify hydration status. At the same time, capillary blood samples were taken to determine hematocrit, plasma urea, and plasma sodium....
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