Relationship of fibre number among muscles in the laboratory rat


The purpose of this study was to determine whether or not the fibre number in one muscle of an animal (relative to fibre number in the same muscle of other animals) could be used to indicate relative fibre number in other muscles within the animal. Ten male Sprague-Dawley rats selected for the largest variation for fibre number in the soleus muscle were used as subjects for the study. Fibre number was then determined for the following 8 muscles in each of the animals: plantaris, gastrocnemius, rectus femoris, vastus lateralis, extensor digitorum longus, tibialis anterior, biceps brachii, and the long head of the triceps brachii. Spearman correlation coefficients were used to make comparisons of relative fibre number among muscles and between each individual muscle and the total fibre number from the 9 muscles used from each animal. The results indicated that relative fibre number from one muscle could predict relative fibre number from another muscle in 64% of the possible comparisons (46 out of 72). The comparisons of relative fibre number for each individual muscle to total fibre number indicated that each of the 9 muscles studied could be used to predict relative total fibre number. The results of this study indicate that relative fibre number from a small muscle in the body can be used to predict relative total fibre number in the body.

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Journal of Anatomy