Exercise-induced rhabdomyolysis is an increasingly frequent cause of hospitalisation and is much debated in the media. The real incidence of the condition is unknown. We wanted to investigate changes in creatine kinase (CK) levels in healthy students following intensive exercise and to look for a correlation between CK, pain and previous exercise history. Twenty-four healthy students performed a single intensive workout and acted as their own controls with testing before and after the exercise session. All participants displayed an increase in CK levels after the workout, 58 % to above 5 000 IU/l. CK rose from a median of 104 IU/l (72-212) to a median of 6 071 IU/l (2 815-12 275) on day 4, p < 0.001. A negative Spearman's rank correlation was observed between the frequency of strength training prior to the experiment and the CK increase, rho = -0.477 (p = 0.021). A major increase in CK levels is a normal phenomenon after intensive exercise, and the amount of the increase is related to previous exercise history. Further studies should evaluate whether patients with exercise-induced rhabdomyolysis should receive the same treatment as those with rhabdomyolysis caused by other mechanisms.