DNA immediately after exhaustive exercise and its disap-

pearance within 2 h after the race suggests that cell-free plasma DNA could possibly be an important tool for monitoring and quantification of cellular damage. Experiments are ongoing in our laboratories to determine whether apoptotic or necrotic events are responsible for the observed phenomenon. Although it seems likely that the source of cell-free plasma DNA is the skeletal muscle cell, further investigations are needed to determine whether other cell types are involved as well.