Muscle carnitine level in endurance training and running a marathon.

Twenty sedentary volunteers (13 men and 7 women) who were subjected to an 18- to 20-month training program aimed at completing a marathon after the onset of training participated in this study. In the course of the training and after running a marathon, the content of total carnitine in the m. vastus lateralis did not change. The content of muscle total carnitine was not sex related. However, significant correlations were demonstrated between muscle total carnitine content and plasma urea and creatinine concentrations. Also a negative significant correlation was found between the content of muscle total carnitine and the plasma activity of CK before running a marathon.