Distribution of different fiber types in human skeletal muscles: why is there a difference within a fascicle?

The proportions of different fiber types (type 1 and type 2) on the borders of fascicles are shown to differ from the proportions internally. This finding is based on the analysis of a total of 245 fascicles from whole cross-sections of the vastus lateralis muscle from 13 men, aged from 26-80 years. Generally, the difference is more marked in the young than in the old. It is argued that the causes of this difference are likely to be local factors in the muscle.