A muscle is a series of fibers bunched together. These fibers have the ability to contract and shorten to produce specific movement in the body. Each part of the body is composed of a particular set of distinct specialized muscles designed to aid in the functional movement of that area of the body. The intermuscular septum separates each different muscle.
Comprised of sheets of thin fibrous material, the intermuscular septum binds muscle fiber together to form each muscle. These fine membrane-like coverings also serve to connect bundles of contractile fibers to the bones. It is this connection to the bones of the limbs that allows the arms and legs to move.
Also referred to as fascia, the intermuscular septum is mostly comprised of connective tissue. This layered collection of closely packed collagen fibers has the ability to withstand the stress exerted upon it when the group of muscles fibers located within its confines contacts and relaxes. The ability of this membrane to stretch permits the arms and legs to move smoothly and purposefully.
In addition to bundling muscle fibers and connecting each muscle to a bone or bones, the intermuscular septum plays an important role in reducing the friction or rubbing force produced when muscles tighten or contract. This allows each different muscle to act separately to produce movement. For example, when flexing or bending the elbow, the bicep muscle, situated in the front of the upper arm, needs to contract of tighten to move the hand towards the shoulder. Simultaneously, the triceps muscle, located in the back of the upper arm, must relax or lengthen.
Without the intermuscular septum separating, grouping, and linking muscle fibers together, it would not be possible to create purposeful movement; the fibers would lack organization. In addition, the body would have to call upon each individual muscle fiber to fire instead of mobilizing a group of fibers to fire simultaneously and in unison. Without this separation it would also be difficult to make some fibers contract while others relax, a necessary component for controlled movement of the arms and legs.
Another important role of the intermuscular septum is to define muscle bulk and give the body its shape. If the muscle fibers, or the single muscle cells, were not grouped together the body would lack distinct form and contours. It would also be difficult to strengthen individual muscles, as the fibers would intermix.