Origin vs. Insertion

When talking about muscular attachments, it’s important to know and understand the difference between the origin and insertion. They are not interchangeable and have totally different meanings, though you can say muscular attachment or attachment site and be talking about either the origin or the insertion. 

What’s the difference? 
When a muscle contracts, the origin pulls the insertion closer.  Always! Muscles pull. The origin is the fixed point that doesn’t move during contraction, while the insertion does move. Your bones are the levers and your muscles are the pulley. Basically, we are all super complex puppets on strings. To explore this further, let’s take a look at the rhomboids. 

Rhomboids Minor and Major

Rhomboids Minor and Major

Firstly, there are two rhomboids and they’re both deep to the multidirectional fibers of the trapezius. Rhomboid minor sits on top of, or superior to, its larger counterpart rhomboid major. Minor originates on the spinous processes of C7 and T1 while major originates on the spinous processes of T2-T5. You can pretty easily feel for T1 on yourself, it’s just at the base of the posterior neck and it bumps out a little bit posteriorly. The transverse processes stick out to the sides while the spinous processes, which we are talking about here, stick out and a bit downward posteriorly. They remind me of a stegosaurus. It’s from these little posterior projections that both rhomboids originate. 

Back to rhomboid minor, it inserts on the upper portion of the medial border of the scapula, across from the spine of the scapula. The insertion for levator scapula is right there too and is easily palpable on yourself or someone else. Rhomboid major inserts on the medial border of the scapula as well, basically between the spine of the scapula and the inferior angle of the scapula. The actions of the rhomboids are to retract or adduct the scapula, elevate the scapula and also downwardly rotate the scapula.

How does a muscle that elevates the scapula downwardly rotate it as well? If you look at the direction the fibers run, they’re on a bit of a downward angle going from the spine to the scapula. Because of this, when the muscles contract, they have the pulling capacity to draw the shoulder blades closer together. Downward rotation can be a tricky one because the scapula is the only bone in the body to do it, but we’re referring more specifically to the movement of the acromion, which is the flat bony process at the lateral end of the posterior scapula. When the rhomboids contract, they have the ability to tilt the acromion downward. It’s a slight action but it’s there nonetheless. Lastly the rhomboids can also elevate the scapula as a whole. Every time the muscle contracts (concentrically, that is, but that’s another post for another day), the origin says ‘come to me’, and so the insertion does. This is true for all the muscles in the body.

When studying anatomy, learn to look closely at the direction of the muscle fibers, and determine which end is the origin and which end is the insertion. That information will take you a long way in figuring out what actions a muscle can do.

Let’s look at a neck muscle- the sternocleidomastoid, or SCM. It has two heads which means it originates in two spots: the top of the manubrium (sternum) and the medial third of the clavicle. Its insertion is up behind the ear on the mastoid process and the outer portion of the occiput. When both the left and right right SCM contract together, the origin (which is down on the clavicle and sternum) pulls the insertion toward it to create neck flexion and also assist to lift the rib cage to make more space for inhalation. 

My hope is that this makes sense but if you don’t understand and would like to, please send me an email and I’ll break it down even more! If you’re teaching and get confused about what’s the origin and what’s the insertion, you can simply say attachment. But do trust yourself! If you take a moment to think about how the body moves and works, and you know the origin is fixed and the insertion moves, you can likely figure it out for yourself. 

Kinesiology Lingo: Movements of the Body

When we talk about a direction the body is moving, we are always looking at it from anatomical neutral regardless of which position we are in.  For example, the hairy side of my forearm is always the back of my forearm whether my palms are facing forward or behind me (and the smooth side is always the front).  To be in anatomical neutral means you are standing upright with the arms hanging by your sides, palms open and forward facing.  Whether you are on your front, back, side, upside down or right side up, the front is always the front and the back is always the back when it comes to describing these movements.  


Flexion starts with an F.  Let this remind you of ‘forward’ or ‘front’.  Also think about when you flex your biceps brachii, you bend the elbow and curl it in.  Most joints are flexed when you’re in child’s pose, or when you are born in the fetal position.   If your spine is flexed, it’s rounded.  If your fingers are flexed, they’re curled in toward your palms, if your neck is flexed your chin is tucked to your chest, if your wrist is flexed your fingers are coming toward what we call the inner wrist but anatomically speaking it’s actually the front of the wrist. If the knee is flexed it’s bending, if the hip is flexed the knee is coming up toward the chest, etc.  Just remember:  flexion = forward.  This action occurs at many joints and always brings the bones that make up a joint closer together, or closes the joint.  

Extension is the opposite of flexion, which means it lessens the angle between the two bones or opens the joint.  In wheel pose (a full backbend), the hips, spine and wrist are extended.  When you’re in crescent lunge pose, your back leg is extended (hip extension via the glutes). When you lift your knee to your chest and then kick the leg straight out in front of you, that’s extension of the knee (but flexion of the hip).  Think about it:  the knee joint is open but the hip joint is closed.  When you lift into cobra pose, that’s extension of the spine.  

This can also be called internal rotation.  These directions and terms are all in relation to the midline of the body so medial rotation means coming in toward the midline.  The median is always in the middle of the road.  Medial means toward the middle. This occurs at the shoulder and hip joints, and because there is a small amount of medial and lateral rotation available at the knee the tibia can be medially or laterally rotated as well.  For the most part though, consider both medial and lateral rotation as movements of the shoulder and the hip.  In warrior two, your back leg (the straight one) is medially rotating.  When doing cow’s face arms (I still don’t get why they call it that), the bottom arm is medially rotating.  In other words, if you have an itch on the middle of your back and you reach around to scratch it, your shoulder is medially rotating.  Or if you go to unhook your bra, your shoulder is medially rotating.  

This is also sometimes called external rotation, or rotating away from the midline.  When you’re standing with your arms by your side in tadasana and you turn your palms forward, your shoulders are laterally rotating.  The top arm during cow’s face pose is laterally rotating.  Pigeon pose laterally rotates the hip.  The front leg in warrior two is laterally rotated.  

A rotation can be either medial or lateral but when we are talking about rotation on its own, we are referring specifically to the spine.  Rotation occurs only along the axial skeleton which means the head and vertebral column.  When you look over your shoulder, that’s rotation of the head and the neck.  When you’re standing with your feet planted and you turn and reach for something to your right, that’s rotation of the trunk.  Any twisting pose in yoga requires rotation.  

This action occurs only at the scapula and it refers to the movement of the acromion.  It is possible to upwardly rotate the scapula without elevating the whole thing.  The inferior angle of the scapula swings outward when upward rotation occurs.

Also only occurring at the scapula, this is the opposite of upward rotation.

The ribs elevate on the inhale.  When you lift your shoulders to your ears, you are elevating the scapula. When you close your mouth, you are elevating the mandible (jaw bone).

Exact opposite of elevation.  If it can be elevated, it can be depressed.

Lateral flexion only occurs along the axial skeleton as well, so this action is available at the neck and spine.  If you drop your right ear to your right shoulder, that is lateral flexion of the neck.  If you’re bending to one side or the other, that is lateral flexion of the spine. 

Abduct means to take away and in this case abduction means to take away from the midline.  This action is available at the hip and shoulder, both ball and socket joints.  If you’re standing in neutral and take an arm or a leg out to the side, that is abduction of the shoulder or the hip.  The deltoid produces this action for the shoulder and the gluteus medius, which is sometimes called the deltoid of the hip, does it for the hip.  You can also use the term abduction in place of protraction for the scapula, as protracting the scapula means you’re moving it away from the midline.

Adduction is exactly the opposite of abduction and therefore it means to add something back to the midline. It’s available at the hip and the shoulder, and you can call it adduction of the scapula as well but I prefer to say retraction. 

To retract is to pull back.  You can retract your mandible (jaw) by contracting the temporalis muscle.  You can retract the shoulder blades by engaging the rhomboids major and minor.

You guessed it... protraction is the opposite of retraction.  To protract the mandible would be to stick the bottom jaw out.  

Circumduction happens at the hip and shoulder and involves a combination of adduction, abduction, flexion and extension all at once.  Making hip or shoulder circles is circumduction. 

To be in the supine position means to be on the back.  When you’re lying in savasana, you are lying supine.  If your palms are up when you’re in savasana, your forearms are supinated.  If you’re going to hold a bowl of soup, you need to supinate in order to do that (little word tricks like that have always helped me remember things better).  Some people say the feet are either supinated or pronated, but a better term for that would be inversion/eversion (more on those in just a moment).  Supination occurs at the forearms (thanks to the radius) and is also used to describe the position of the whole body (on the back is supine, on the belly is prone, which leads me to our next topic)…

Put your forearms and elbows on a table, keep everything else still and turn your palm down.  That is pronation of the forearm, again, thanks to the radius.  When the forearms and elbow are on the table you’ll notice that the ulna (pinky side) stays put while the radius (thumb side) spins to create the pronation and supination of the forearm.  If you’re in dolphin pose (without clasped hands) or setting up for a forearm stand, the forearms are pronated.  

These last four actions all occur at the ankle joint, or talocrural if we’re speaking anatomically.  While we do have the ability to roll the ankle around, take note the next time you do that that you aren’t making a full circle like the hip does during circumduction.  The distal (far) end of the tibia (shin bone) articulates with the talus, which is one of the 7 tarsal bones to create the following four actions:


If you’re standing in tasadasa, and you roll toward the outer edge of your foot to lift the inner balls of the feet, this is called inversion.  The soles of the feet are moving IN toward the midline, this is called INversion of the ankle.

If you’re standing in tasadana and shift your weight inward to the balls of your feet to try to lift the pinky side of the foot, this is eversion.  E for external, you’re opening the sole of the foot to the outside.

This is more commonly called flexing your foot, or pulling your toes back toward your shin bone.  It may be a little confusing but the top part of the foot is called the dorsal surface and dorsal means back.  The top of your foot is actually the back of your foot.  Think about it: when you’re in child’s pose (or being born), you’re all curled up.  All of the surfaces that are closed in and protected are on the front side of the body.  If we could look at a 3D image of you in child’s pose (wouldn’t that be cool?), all of the surfaces pointing outward are the back side of the body, and that includes the tops of your feet.

Stepping on the gas pedal, balancing on the balls of your feet and pointing your toes like a good ballerina are all examples of plantar flexion.  The plantar surface of your foot is the bottom of your foot.