Rested and exercise-stressed lambs were slaughtered and dressed. The carcasses from half of the rested and exercise-stressed groups were electrically stimulated 30 min after slaughter and all carcasses were moved into a freezer 2 h postmortem. Tenderness was assessed on legs and loins roasted from the frozen state. The rested lambs were extremely tough unless the carcasses had been electrically stimulated but, if stimulated, were moderately tender. The exercise-stressed Iambs went into rigor rapidly with high ultimate pH values in leg and loin muscles. The legs and loins of exercise-stressed, non-stimulated animals were tender but the legs were toughened by stimulation. It is likely that this toughening is the result of rigor occurring during or soon after stimulation so that no relaxation of muscles can occur when the stimulating current is switched off.
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