ABSTRACTAdvanced myofibrillar degeneration with changes of I‐bands and Z‐discs was noted in electrically stimulated samples as early as the day of slaughter. Occurrence of the proteolytic changes observed paralleled rate of depletion of muscle energy stores during electrical stimulation and subsequent improvements in tenderness. Localized supercontractions have been implicated as one cause of improved tenderness of electrically stimulated bovine carcasses, as has enhancement of autolytic proteolysis. Contracture bands occurred in both nonstimulated and electrically stimulated samples in the early postmortem period. Contracture bands are a common artefact in improperly prepared tissue preparations, therefore they are not a specific effect of electrical stimulation. Improved tenderness of ES samples could more easily be explained by an accelerated autolytic proteoly