Effect of oral creatine supplementation in soccer players metabolism

The aim of the present study was to assess whether creatine can alter the metabolism of nitrogen compounds and performance in professional soccer players. The subjects were randomly divided into 2 groups: experimental (E; n = 17) and control (C; n = 14). Their initial evaluations included blood tests and nutritional intake. They then received a supplement consisting of 20 individual doses of creatine to be taken orally for 5 days, totaling 0.6 g. Kg-1 body weight per day (group E = 50% creatine + 50% dextrose; group C = 100% dextrose). On day 5, blood was collected from the resting subjects (PRE), and then 10 min (POST10) and 20 min (POST20) after they underwent an ergometric test. Nitrogen compounds and hematocrit were measured in each blood sample. There were no differences among the groups in the results of the physical examination, nutritional state, blood samples or performance. Serum ammonia levels measured after exercise were equal to those at rest. Serum urea increased in POST10 and POST20. In Group E, uremia was lower than in Group C in PRE, POST10 and POST20, indicating retention of protein and nucleotides.