Fig. 1 shows the pro®le in a values during storage of fresh and aged LT and PM muscle. The a values in aged muscles were much higher than in fresh muscle.This is likely to be caused by an increase in scatter due to the ageing process, as well as a better oxygenation because muscle respiration is absent in aged muscle. In fresh LT and PM muscle a-values were fairly stable during the storage period, while they decreased somewhat more rapidly in aged muscles. In comparison with fresh muscle, the variation in a-values within treatment groups is increased in aged muscle