Exercise-induced muscle damage and inflammation: fact or fiction?

Physical exercise is necessary for maintaining normal function of skeletal muscle. The mechanisms governing normal muscle function and maintenance are vastly unknown but synergistic function of hormones, neurosignalling, grow th factors, cytokines and other factors, is undoubtedly important. Because of the complex interaction among these systems the lack of complete underst anding of muscle function is not surprising. The purpose of exercise-induce d changes in muscle cell function is to adapt the tissue to a demand of inc reased physical work capacity. Some of the approaches used to investigate c hanges in skeletal muscle cell function are exercise and electrical stimula tion in animals and human models and isolated animal muscle. From these mod els, it has been concluded that during physical exercise, in an intensity a nd duration dependent manner, skeletal muscle is damaged and subsequently i nflamed. The purpose of the inflammation would be to repair the exercise-in duced damage. Because of the design and methods used in a majority of these studies, concerns must be raised, and the question asked whether the parad igm of exercise-induced muscle inflammation in fact is fiction. In a majori ty of conducted studies, a non-exercising control group is lacking and beca use of the invasive nature of the sampling methods used to study inflammati on it does not appear impossible that observed inflammatory events in human skeletal muscle after physical exercise are methodological artefacts.