How much can exercise raise creatine kinase level-- and does it matter?

Moderate-intensity exercise (maintaining heart rate between 55% and 90% of maximum) may elevate creatine kinase (CK) to levels that meet the diagnostic criteria for rhabdomyolysis if the exercises involve eccentric muscle contractions, such as weight lifting or downhill running (strength of recommendation [SOR]: C, small observational studies). The clinical significance of exercise-induced elevations in CK is unclear because the renal complications associated with classic rhabdomyolysis haven't been observed