What Is the Definition of Muscle Origin?

Definition and Discussion

A simulated image of the upper back of a skeleton shows muscle origins, insertions and bellies.
A simulated image of the upper back of a skeleton shows muscle origins, insertions and bellies.. lookaround

Muscle Origin Definition and Discussion

Muscle origin is a term referring to one end of a muscle, generally at the location where it attaches to a bone.  The main part of the muscle, called the belly of the muscle, then crosses over the gap between this bone and another usually adjacent bone - to attach there.  The end of the muscle that attaches onto the 2nd bone is called the insertion.

Muscle origins and insertions are also called muscle attachments.

  When you phrase it this way, you are not distinguishing the type of attachment.  In other words an attachment can be either an origin or an insertion, or with a plural usage, both.

Muscle origins are distinguished from muscle insertions by the relative degree of movement (and therefore the role in movement) of the bone to which they attach when you perform common motions.

Muscle origins generally attach to bones that provide stability.  

Origin and Insertion Role Reversal

That said, it’s possible to reverse the roles of the bones (and their muscles) that are involved in a common movement so that the usually mobile part provides the stability and the usually stable part does the action.  In this case, though, the motion will be very different than the original version.  Not only that, the resulting action serves an entirely different purpose. You can learn more by reading about the gluteus medius muscle.

This kind of reversal can be valuable as you do strengthening and/or flexibility exercises. By working the joint from the opposite-from-usual perspective, you may find new muscle fibers to work, and train them to function for you in more than one situation. Plus, you'll likely increase strength through a larger range of motion - a great way to decrease your risk for injury.

Pilates machine workouts are known for this type of training.  If Pilates is too expensive for you, consider using a theraband and/or tubing.  About.com's Exercise Expert, Paige Waehner, has a good routine for beginners:  Theraband routine.  

With most of band exercises, you'll get a chance to work all the muscles around a joint using at least 2 types of contractions.  The key to a great workout here is to keep a slow speed speed both there and back without sacrificing good form.  You'll see what I mean after a couple of reps.

Muscle Attachment Knowledge for School

When you study muscles and joints for school, you’ll need to learn the exact locations of the muscle origins and insertions - along with other information such as the action they produce for the joint.  You may also need to know the nerves that supply the muscle.  Keep in mind that muscle origins and insertions sometimes attach on several places on their respective bones, and your teacher will probably require you to know all of them.

 

To recap, and propel your studies forward, here are 4 handy points for understanding the role muscle origins and insertions play in human motion:

  • Muscles are power engines for movement; they attach to bone on either end, crossing the joint as they do.
  • The part of the muscle located between 2 ends is known as the belly of the muscle.
  • Movement happens at joints, with one bone of the joint moving freely as the other remains stationary.
  • All of this is significant because the size, direction and shape of the muscle belly and muscle attachments are part of what determines the range of motion of the joint, and therefore its flexibility.

Related:  Soft Tissue

 

 

 

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