5 (±28.6) min. remained no longer statistically significant when adjusted for the personal best time in a 100 km ultra-marathon. Personal best time proved to be an important variable regarding performance in ultra-endurance races [37]. Thus, adjusting for personal best time resulted in a non-significant difference in

race time between the two groups. The number of athletes might also have affected the result. A decrease of 0.6 kg in body mass seems to be relevant. In a recent study of male 100 km ultra-marathoners, skeletal muscle mass decreased by 0.7 C188-9 in vitro kg [2]. Regarding statistical power, we would have needed to include 42 subjects per group to detect a clinical relevant difference between the groups of 80% power. With our actual sample size, we had only 60% power. However, it was not possible to increase the sample Belinostat cell line of athletes under field conditions since only these 28 ultra-marathoners from the total field of athletes volunteered to participate. Since variables of skeletal muscle damage, such as creatine kinase and myoglobin, remain increased for up to seven days after a marathon [38], they should be measured not only immediately

after the race but also in the recovery phase. Presumably the intake of amino acids during the race would lead to lower values of creatine kinase and myoglobin in the recovery phase. In a multi-stage ultra-endurance run, skeletal muscle mass decreased continuously throughout the race [11, 12]. Presumably, amino acid supplementation would have an pheromone effect on variables of skeletal muscle damage Mizoribine mouse rather in a multi-stage race than in a single ultra-marathon. It has been shown that the oral administration of amino acids resulted in a faster recovery of muscle strength after eccentric exercise [39]. The

ingestion of protein during rest periods might enhance recovery [40]. In runners, especially, the combined ingestion of carbohydrate and protein after each training session over 6 days reduced the post exercise increase in serum creatine kinase and muscle soreness [34]. Conclusions The ingestion of 52.5 g of amino acids immediately before and during a 100 km ultra-marathon had no beneficial effect on variables of skeletal muscle damage, muscle soreness, and race performance. A positive effect of amino acid supplementation in ultra-runners might be expected when amino acid or protein would be supplemented in the rest period during a multi-stage ultra-endurance run. Recovery might be enhanced and increase in variables of skeletal muscle damage might be reduced, effects that should be investigated in future studies. Acknowledgements We thank Mary Miller for her help in translation. References 1.