Updated publication reference for PubMed record(s): 31443506, 31080489. Muscle atrophy is one of the main deleterious consequences of ageing and physical inactivity. Although basic knowledge regarding the underlying mechanisms of muscle atrophy is continuously growing, there are still no efficient therapeutic strategies for its prevention and treatment. Hibernating bears exhibit a strong and unique ability to preserve muscle mass in conditions where muscle atrophy is observed in humans. However, underlying mechanisms have not been understood yet. To fill this gap, the aim of this study was to characterize changes in the bear muscle proteome during hibernation versus the active period. Muscle biopsies were obtained from Ursus arctos bears.