The complex arrangement of muscle fasciculi is seen when meat is carved, and the same complexity is found in the muscle fibres that are bound into these bundles. Their complex arrangement is related to muscle function in the live animal. It used to be thought that muscles which contracted to a relatively small fraction of their resting length had fibres parallel to the long axis of the muscle, whereas muscles in which the strength of contraction was more important than the distance over which contraction occurred had fibres with an angular arrangement. Thus, it was thought that muscles might gain strength by leverage, but the contraction distance would be reduced. If a small chunk of meat is placed under a dissecting microscope and teased apart with needles, the smallest fasciculi visible without magnification are composed of bundles of muscle fibres.
Muscle fibres are the basic cellular units of living muscle and of meat.
The muscle fibres found in most commercial cuts of meat seldom run the complete length of the muscle in which they are located. Apart from tapered intrafascicular endings, the diameter of a fibre is assumed to be approximately constant along its length. Fibre diameters slowly increase during the growth of a muscle, but they also increase temporarily when a fibre contracts. Thus, when measuring fibre diameters in a growth study, special care must be taken to avoid or to correct for differences in the degree of muscle contraction. The simplest way to examine individual muscle fibres is to place some meat fragments together with some water in a kitchen blender.