[Change of body composition in an 81 year old runner in a 100 km run]

An 81-year-old runner completed successfully a 100-km-run within 19 h 45 min one year after coronary artery bypass surgery in recently diagnosed atherosclerotic coronary heart disease. Prior and shortly after the run, percent body fat, lean body mass, skeletal muscle mass and percent body water were determined non invasively both by the bioelectrical impedance analysis (BIA) and the traditional anthropometrical method. In addition, blood and urine samples were collected in order to evaluate fluid homeostasis. Proton nuclear magnetic resonance ((1)H-NMR) spectroscopy of the urine was performed in order to detect changes in metabolites of carbohydrate, fat and protein metabolism. Body mass increased by 1.9 kg, calculated skeletal muscle mass increased by 0.1 kg, calculated fat mass from anthropometric method decreased by 0.2 kg and from BIA by 3.1 kg. Calculated body water from BIA increased by 1.2 l and plasma volume decreased by 19%. Haematocrit, nitrogen urea, urinary specific gravity decreased whilst sodium increased. (1)H-NMR spectroscopy revealed an increase of ketone bodies after the run. To demonstrate a decrease of skeletal muscle mass after a 100-km-run, we should wait with the measurements of body masses until body water has reached pre race value. The increase of body water is unclear. In future studies, additional methods should be performed to provide information whether skeletal muscle mass decreased after endurance performance and whether metabolites of skeletal muscle mass degradation may impair renal function.