Serum creatine kinase activity following a 120-km march.

Serum creatine kinase (SCK) was measured in 19 well-trained athletes before, immediately after and 24 and 72 h after a 120-km, non-stop march. The mean level before the march was 97.6 +/- 46.6 (SD), immediately after the march 1072.8 +/- 708 microns/l, and 72 h later 185.6 +/- 106.2 microns/l. It is concluded that elevated SCK levels may persist for 72 h after a long march.