Extensorville Part 1
Remember Baby J and the development of his extensor system?
See blog post here https://mewithlauriebb.com/baby-j-shows-us-how-to-develop-our-extensor-system/
and review the short video of Baby J showing us how it’s done! https://youtube.com/shorts/SDDKckKN17c?feature=share
Co-contraction of the Flexor and Extensor System
We are born in flexion.
We develop the extensor muscle system once outside the womb.
You can see Baby J moving his head and neck, his arms, his legs, while on his belly in the video – he’s doing the developmental work, his own type of strength training against gravity.
As he develops these extensor muscles, a co-contraction between flexor and extensor muscles around his joints can occur, allowing for improved joint stability and movement accuracy/efficiency.
You can think of co-contraction as a dance of one set of muscles partnering with another under the guidance of your central nervous system.
The flexor muscle groups sometimes have to shorten and contract while the extensor muscles lengthen and vice versa.
Gravitational force acts on our bodies at all times.
We need help resisting that force and in comes co-contraction to the rescue!
The co-contraction of flexors and extensors is an enormous biomechanical and neural interaction allowing us to function in everyday life.
So it’s a brain and body thing – all movement is, which is why movement/exercise is now being linked to the reduction of cognitive issues.
But I digress…
You can’t sit up unless you have muscle co-contraction between flexors and extensors.
You certainly can’t walk if you don’t have this co-contraction.
You really can’t do most activities of daily living without the postural control that comes with the co-contraction of flexors and extensors.
And that means a strong extensor system that cohabitates and shares the work with the flexor system.
What are the extensor muscles and what do they do?
The extensor muscles “open” the joints or “extend” them by increasing the angle between bones at a joint.
Think… the “un”fetal position.
Now this post gets a bit hairy in terms of anatomy.
If you love the detailed anatomy stuff and all the verbiage read on.
If you aren’t so interested in that, here’s the cheat sheet and then just scroll down to the next section or take a look a the highlighted words in this section.
Joints that extend – elbow, wrist, fingers, shoulder, thumb, hip, knee, ankle, toes, neck, spine.
When you lengthen your elbow, the angle between the forearm and upper arm increases as the ulna (forearm bone on pinky side) moves away from the humerus (upper arm bone).
The triceps, as the prime mover for elbow extension, are responsible for this movement.
Shoulder extension occurs when the angle of the arm (humerus) and scapula increases.
The latissimus dorsi, teres major and minor, and posterior deltoid muscles are the main extensor muscles for this movement.
Wrist extension is moving the palm of the hand away from the anterior surface of the forearm (the side of your forearm aligned with your palm), increasing the angle.
It’s the hand/wrist position of cat/cow or plank.
There are several prime movers that live in the forearm to make this wrist action occur – extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris.
++++++I’ll never forget the amazement I felt when I first saw a human cadaver forearm and the intricate network of muscles that make the wrist and hand move! The fingers move because of what the forearm does!
When the fingers lengthen away from the palm (don’t make a fist), that is finger extension.
There are three main muscles that make the fingers extend and all of them begin in the forearm – extensor digitorum, extensor indicis (extends the index finger), and extensor digti minimi (extends the baby finger).
Thumb extension is when the thumb moves out to the side away from the palm.
I think it’s important to include the thumb since it’s a fairly common site for osteoarthritis.
The extensor pollicis longus and brevis muscles, located in the lower forearm, make this happen.
Side note... for those of us who have pain in our thumb, hands, and/or wrist, it is wise to consider what is above this area, including the forearm, elbow, shoulder, and the integration into the trunk.
The angle between the femur and pelvis increases in hip extension and the leg moves back posteriorly.
The primary hip extensors are the gluteus maximus, the hamstings, and the posterior head of the adductor magnus (this is an inner thigh muscle and something that yoga and movement teachers may not include when speaking of hip extension and it’s super important as a prime mover in hip extension).
To all of us who “butt tuck” on a regularly basis, we are doing our hip extensors no favor. Let’s untuck and let the hip extensors sing and live free!
Knee extension is interesting. When the knee lengthens the angle between the femur and tibia increases – it’s one of the only joint extensions that doesn’t move backwards/posteriorly.
Quadriceps are queen here. It’s interesting to note that the quadricep is also a prime mover in hip flexion.
Plantar flexion of the ankle is extension of the foot at the ankle.
The gastrocnemeus, soleus, and plantaris are the muscles allowing us to plantar flex – rise up on the ball of our feet or “point” the foot.
Toe extension is lengthening the toes, increasing the angle between the tip of the toe and the sole of the foot.
The prime movers of toe extension are extensor digitorum brevis and extensor hallucis brevis.
Neck extension is when the angle between the head and trunk increases – think looking up at the sky or dropping your head back in camel pose.
The prime mover of neck extension is the sternocleidomastoid, but there are suboccipital muscles and parts of the erector spinae that also help this process.
Spinal flexion
Spinal Extension – holding trunk upright against gravity
Spinal extension backbend with neck extension
Spinal extension is the increase of the angle between the spine and hip.
Standing in tadasana is spinal extension – a large co-contraction of muscles in the flexor and extensor groups. Your rectus abdominus must lengthen in the front body while your erector spina in the back body shorten to hold your trunk up against gravitational force.
Taking the trunk backwards in tadasana towards a backbending position is also spinal extension and increases the need for the front body to lengthen as the back body shortens.
We’re going to keep this simple and say the main spinal extensors are the erector spinae – the ES are a large superficial group of three muscles that span the neck to the pelvis, running more or less vertically along the spinal column on either side. There are more muscles involved in spinal extension, but the minutiae will get intense if I go on about it.
Bottom line… we must develop a lot of muscles after exiting the womb in order to get up and be bipedal animals moving through the world performing activities of daily living.
My Observations on Extensor Muscle Actions
I often observe several areas of what I might call extensor strength deficits in my work.
These tend to be glutes, hamstrings, shoulders, and parts of the spinal region.
Regular strength training is probably the absolute best way to build strength and capacity in the extensor muscles – squats, lunges, deadlifts, pull ups, push-ups, rows with increasing load.
In terms of the shapes and postures we practice in yoga? Look at Baby J in his short video.
He’s got the whole salambasana thing going on.
Salambasana is a movement/shape that requires many of the extensors to contract/shorten around joints – calves, knees, hips, spine, shoulders, elbows, fingers, toes.
The muscles around these joints shorten against the force of gravity while the flexors lengthen – it’s that co-contraction I was talking about earlier.
In order to build strength in this posture, it may require more than simply moving into the pose and holding it, although there is nothing wrong with that.
I would suggest moving into the posture slowly, holding for a couple seconds isometrically, and then slowly releasing to tap the floor and repeating this process for 10 repetitions. Once you’ve built the endurance and strength, add a second set.
See video demo here: https://youtu.be/4UoRJPuXyoU
—-You must decide how many repetitions feel ok to you right now and understand that 10 is a rather arbitrary number and adding a second set may come after some weeks of regular practice of numerous reps. This is only a suggestion of how to perform salambasana to increase strength and endurance for a great number of the extensor muscles—–
There are ways to add external load, but I’ll get into that in one of the following posts.
As always, let me know what you think, if you’ve learned anything from this post, if you have questions or comments.
In gratitude,
Laurie BB
