The wrist, the shoulder, and connections

This is a blog about the wrist and how it moves. It’s also a blog about the shoulder, which influences the position of the hand (or maybe the hand influences the position of the shoulder?). Mostly, this is a blog about helping people understand the relationship between the hand and the shoulder during movement skills. But first, it is important to gain a tiny glimmer of anatomical knowledge.

Anatomy:
The wrist contains ten small carpal bones, two of which meet with the radius and allow most wrist movement to take place (Hamill & Knutzen, 2006). These bones, the scaphoid and the lunate, meet with the radius to form the radiocarpal joint. This is where wrist extension and radial and ulnar flexion occur; wrist flexion, however, occurs mostly at the midcarpal joints. The scaphoid bone is particularly important in transmission of force from the hand to forearm when the hand is fixed, such as in a push-up position. The wrist has the ability to flex from 70-90 degrees, though researchers suggest we only use 10-15 degrees of flexion for most activities of daily living (ADLs). The wrist has the ability to extend between 70-80%, though ADLs only require approximately 35% of range of motion. 

Before we go on, if you regularly teach any sort of position where a client or student is loaded on his hands, what are the chances the individual has the ability to adequately extend his wrist to effectively deal with load? And what happens if he doesn’t have either the motor control or mobility to deal with the weight of his upper extremity? 

Onward. So the wrist allows flexion, extension, and side to side motion. How much the wrist can do these things depends on the position of the fingers. If the fingers are flexed, a person generally has greater extension but less flexion, while if the fingers are extended, the same person will have less extension, more flexion. 

From a joint mobility perspective, it could be argued it’s probably worthwhile to perform mobility exercises with the fingers extended and the fingers flexed because of increased motor control options and variability. (If you aren’t performing joint mobility exercises for the wrist, hopefully this little bit of anatomy causing you to rethink that particular decision).

The hand is a sensory rich place, with a multitude of muscles that allow movement to occur. I am not going to discuss the anatomy of the hand, except to note that it is quite complex (this is why there are doctors specializing only in hands), and that issues with the finger flexors and extensors can affect the elbow (which makes sense when you consider the muscles that control finger flexion and extension have attachment points near the elbow). The hand is primarily innervated by the radial, median, and ulnar nerves, which allow coordinated, reflexive motor control (Taylor & Schwarz, 1955). 

The muscles that flex the digits and the wrist originate on the medial side of the epicondyle, which makes them supinators of the wrist as well. The extensors originate on the lateral side of the epicondyle, making them wrist pronators. (Supination means the hands turn up towards the sky. I remember this using a trick I learned in college: “if you are carrying soup, your hands are supinated”). 

Now, perhaps you are thinking to yourself, “Wait! You can also turn the hands forward by externally rotating the shoulder!” Or maybe you aren’t, but I am going to tell you that indeed, movement at the hand can be initiated by the shoulder.

Why does this matter? A study performed by Savva, et.al (2003) found strength of supination is stronger when subjects are in more glenhumeral joint external rotation when compared to internal rotation. In addition, grip strength decreases when muscles fatigue while in an overhead position (Kinali, et.al, 2016). Does the fatigue in the wrist affect glenohumeral joint position? Or does fatigue in the glenohumeral joint affect the grip? (This is kind of like the chicken and the egg argument for the upper extremity). I don’t have the answer, but by helping people understand the difference and the connection between supination and external rotation, maybe we can improve a sense of strength and stability in the upper limb.

So far, I have made the argument the wrist needs mobility if we are going to load it, and understanding the relationship between the shoulder and wrist might improve an overall sense of stability and strength through the upper limb. Basically what I am saying is mobility is good, strength is good, and we need to work on both of these things to be successful in our exercise and movement endeavors. Let’s look at how this can be applied more practically.

Wrist mobility:
In order to successfully teach wrist mobility exercises, it is necessary for the client or student to understand the difference between moving the hand around the wrist and moving the hand using the forearm. There is a short video below demonstrating the difference between these two movements. Often what you will find (especially in people who aren’t used to moving at the wrist joint), is it very difficult at first to isolate the movement. 
https://youtu.be/72DfZPyJr80

A simple rule of thumb when working on joint mobility is teach people how to flex and extend in the sagittal plane, teach people how to abduct and adduct in the frontal plane, and then teach people how to connect the dots in a circle. This helps with motor control and brings awareness to how the joint works.

Remember when I said when the fingers are flexed the wrist typically has greater extension and when the fingers are extended, the wrist has greater flexion? When you are teaching someone mobility at the wrist joint, have them do with a a closed hand and an open hand. Not only is variability a positive thing, but joint ROM will be different in the two conditions. 

If you are teaching load bearing on the hands, working strength and mobility in the wrist joint is critical for the health of the upper extremity. I use a variation on these exercises from GMB with all of my clients working on quadrupedal movements or arm balances: https://www.youtube.com/watch?v=mSZWSQSSEjE

Supination and external rotation:
Once wrist mobility has been addressed, helping clients understand the difference between supination and external rotation can help with strength and integration of the shoulder and wrist. To teach this, I usually have clients let their arms hang long. I stand in front of the client and ask the client to turn his palms towards me (supination and possibly external rotation). If the client moves only at the elbow (supination), I ask the client to use the shoulder to turn the palm forward (external rotation). If this looks like it isn’t clear, I use a variation on a rolling fist Feldenkrais exercise found here: https://www.youtube.com/watch?v=V4DyNgXsLKg
(I discuss this a bit more in my blog on collar bone cueing).

Understanding the connection between external rotation and supination makes it a lot easier to teach someone how to: 

• not rely solely on internal rotation in a quadruped position
• place weight in other parts of the hand while in quadruped without losing shoulder position (differentiation)
• feel how gripping with different parts of the hand while in a brachiating position changes the sense of integration in the shoulder

These are good things (at least in my opinion). What “optimal” alignment “looks like” could be heavily debated. Rather than rely on a visual sense, I ask for feedback to find out if the person can feel the connection from the hand to the shoulder. If the answer is yes, we are on the right track. (This is very similar to what happens in the lower extremity when teaching foot to hip connection. When a person first feels the connection, it usually feels like a ton of work because it’s different from his usual way of doing the task. Over time, it begins to feel more secure because the load is being dispersed more evenly). By helping people establish internal connections and understand how their limbs support their structure, you give them the opportunity to optimize their physical experience.

Yours in health and wellness,
Jenn

References:
Hamill, J., & Knutzen, K.M., (2006). Biomechanical Basis of Human Movement. Lippincott Williams & Wilkins: Baltimore.
Taylor, C.Cl., & Schwarz, R.J., (1955). The anatomy and mechanics of the human hand. Artificial Limbs, 2(2), 22-35.
Savva, N., McAllen, C.J.P., Giddens, G.E.B., (2003). The relationship between the strength of supination of the forearm and rotation of the shoulder. The Journal of Bone and Joint Surgery, 85(3).
Kinali, G., Kara, S., & Yilidirim, M.S., (2016). Electromyographic analysis of an ergonomic risk factor: overhead work. The Journal of Physical Therapy Science, 28, 1924-1927.