Muscle creatine kinase as a biomarker of muscle injury in soccer

Abstract

The measurement of muscle creatine kinase (CKm) activity in the bloodstream has been used as a parameter for prospecting muscle injuries in soccer. This approach is based on the proposition that intense muscular activity is often associated with structural micro-injuries in contractile components of skeletal muscle. Once installed, tissue damage favors inflammatory activity, leading to the process of muscle pain. Strikinly, there is still no correlation between increased CKm in the bloodstream and the occurrence of muscle injuries, further complicating the interpretation of CKm as a reliable biomarker. CKm is a protein with a relatively high molecular weight and is primarily drained by the lymphatic system in a slow kinetic process which is, therefore, drained by the lymphatic system in a slow kinetic process. Once it enters the bloodstream, the enzyme can be rapidly degraded, being difficult to determine the protein's actual values. Therefore, the increase in CKm in the bloodstream of athletes may be a reflection of chronic muscle contraction, the intensity of training/games in the current period, and delayed-onset muscle soreness rather than direct incidence of muscle injury. Finally, there remains a lack of evidence supporting a direct relationship between increased CKm levels and performance indices.