Muscles, Stretching and the Opposing Forces - Pt 1
Other posts have introduced the mechanics of a movement - and why stretches work to balance action. It was an essential discussion, but let's say for the sake of argument that if we keep this to the things that you can impact - it's better for everyone. We don't typically use ballistic stretching outside of PT and Strength Training appointments. Massage and Neuromuscular therapy do use Passive, and PNF stretches regularly.
We mentioned before that one of the benefits of massage is increased circulation, an increase in the movement of nutrients and lymph (by-product movement) for up to 72 hours after a therapy treatment. The additional impact of stretching is in the production of endorphins, which are the feel-good products involved in the neuroendocrine system. The output of these 'endocrine' factors is responsible for the feeling right, response to relaxing muscles that most people associate with relaxation. The release of these molecules provides 'lock-and-key' receptors on the surface of ALL cells within the central nervous system. Gates on the cell membrane allow endorphins to pass into the nerve cell, where they affect the system by attaching to receptors at the synaptic cleft. In short, they unleash a response or wave of 'resting' potential via the muscle if the rest of the energy and molecules like Na (Sodium) and ATP are present. So the motor end-plate and therefore the muscle belly can return to the non-contracted length and prepare for the next movement from a neutral position (ideal).
The Muscle Spindle Stretch Receptor is the modified muscle cell located in the 'belly' of the muscle of all skeletal muscles. It detects a change in the length and the tension (tone) within the tissue. When a muscle moves, or is stretched, the muscle spindle sends a signal to the spinal cord. This then signals the muscle to contract and resist the stretch - or create the opposing forces which support the movement just far enough - so that there is no over-stretching or tearing or strain on the muscle, tendons or joints. This is known as the 'spinal cord' reflex arc that we started talking about last time.
Forcing a stretch, or overworking a muscle can intensify the firing of the muscle spindle and cause it to contract. This mechanism can block deepening or lengthening of any stretch or movement. The best option when faced with 'tense' muscles or a lack of flexibility or length is to gradually and slowly remove this blockage by working with the spinal cord reflex arc and tissue messaging to decrease the reflex contraction of the muscle (protecting the joint and the attachments of the muscle to the bone). This will allow you to stretch further and go into more profound movement.
The figure at the bottom of the page illustrates a spinal cord reflex arc of the muscle spindle - when talking a muscle into a stretch or extension. In this case we are talking about the latissimus dorsi for the shoulder. This muscles works in opposition to the rotator cuff and pectoralis major (at the clavicle). In addition, we are showing the hamstrings, as these are the muscles previously mentioned in the 'activation' of the knee - that work in opposition to the quads. A signal is being sent from the muscle spindle receptor to the spinal cord, and this signal is then relayed to the motor nerve via the spinal cord - it is signaling the muscle to contract under extension and resist the stretch. This primitive reflex occurs unconsciously in response to a movement, including a lengthening of the tissue. Holding a stretch for 30-60 seconds causes the muscle spindle to decrease it's firing. It is at this threshold of activity that the muscle begins to release - and relax into further movement. Stopping a movement or stretch part-way, or using multiple shorter stretches, also decreases the firing of the muscle spindle and allows the muscle to relax into a deeper stretch.
We can actually 'reassure' a muscle to go further into a stretch, but using up to four shorter stretches and decrease the 'protective' firing of the muscle spindle as we are beginning a movement. It may seem counter intuitive, but by first backing off, or using multiple actions to decrease the reflex contraction of the muscle we are trying to stretch. This allows a more extended Range of Motion or more stretch - which is the philosophy of the PNF. Helping the body move into a higher degree, but helping retrain the muscles into a more extended stretch or less of a reflex contraction. This movement is the opposition we were talking about - the lengthening of muscle to support the main activity of the contracting muscles. In this case, the example of the quads and the latissimus dorsi, and the reflex contraction that occurs to move the hip and shoulder joints is a perfect example. The movement of the joint can activate the tension of the muscles creating the action, but inhibiting and establishing if the lengthening muscles don't allow the activity or if there is so much tension that the Golgi Tendon organs pull too hard in the attachments at the joints and attachments at the bone.
The concept that we want to reinforce is that multiple groups of muscles create the full movement of muscles in their function of posture, exercise, and relaxation. They all have to work together to get the final product we seek, fully flexible and easy muscle contraction and release. We will have more on this next...so let's take one bite of this elephant at a time.
Since we are focusing a different joint - 'let's show this impact to the shoulder, back, rotator cuff and upper chest muscles and the pain of muscles that have overworked for one reason or another. After seeing more than enough frozen shoulder complaints over the years, each case of frozen shoulder is always a little different. They all have one thing in common, which is subscapularis trigger points. To understanding of the impact of these trigger points, releasing them goes a long way towards "removing the nagging pain" of a frozen shoulder.
The Subscapularis Muscle Description
A discussion of anatomy & biomechanics should include a description of the muscle to the shoulder - as the name suggests. The subscapularis muscle is found be neath the scapula or shoulder blade, and between the ribcage. The muscle extends out to the lateral edge, and up to the front of the humeral head in the shoulder joint where it attaches. The contraction of the subscapularis rotates the arm bone (humerous) inward and pulls the arm towards the body (adduction). The purpose of the muscles is to keep the humerous in the shoulder joint, and it is one of the rotator cuff muscles, the subscapularis that acts to hold the glenohumeral joint together during movements of the shoulder joint. To be explicit, it counters the tendency of the humeral head (top of the bone) to slip upward - and hamming the joing - during abduction movements (away from the body).
The Synergy of supporting Muscles: The subscapularis muscle is assisted by the teres major and pectoralis major during medial rotation of the arm, and by the other rotator cuff muscles during stabilization of the glenohumeral joint.
Why the Subscapularis develops Trigger Points and Referred Pain
The subscapularis can harbor up to three trigger points, where the two most common occur near the outer edge of the muscle. The trigger point on the inside edge of the tissue, near the spine is much less common. It is nearly impossible to contact this location by palpation and manual release.
Image of The Subscapularis Trigger Points & Referred Pain
Referred pain from trigger points in the subscapularis is concentrated in the posterior shoulder region. The second area of discomforts spillovers into shoulder blade region and down the back of the upper arm. A unique "symptom" of referred pain around the wrist may occur as well near the watch band may also occur. The typical client is aware of this wrist pain but does not think it is related to their shoulder pain.
Causes of Subscapularis Trigger Points and Pain?
The Causes of Trigger Point pain occurs when trigger points are activated by some form of muscular overload. Some examples of muscular overload specific to the subscapularis muscle include:
- Bracing a fall by extending the arm out at shoulder level, Foosh - or Fall-on-outstretched-had as to grab for a railing, countertop, or another person.
- Repetitive use injuries in sports, such as swimming, throwing a baseball or playing tennis and occur after long periods of arm immobilization, after wearing a cast on the arm
- Sleeping on the side, with the affected shoulder down and the arm pushed forward across the body. The effectively pins the muscle between two bones with a lot of weight on it, for extreme periods of time
Subscapularis Symptoms & Disorders
Symptoms and dysfunctional pain associated with trigger point activity in the subscapularis muscle:
- Severe Pain in the Posterior Shoulder Region: This pain occurs during shoulder movement or when resting. It is generally felt as being deep within the joint.
- Inability to Lift Arm Past 45 Degrees: A client with chronic subscapularis trigger points will be unable to abduct arm (lift it to the side) past about 45 degrees. In early stages, clients may be able to raise their arm but will be unable to reach backward.
- Unable to Reach Across The Body: Client complaints of being unable to reach across the front of the body to their other armpit. This stretch will extend the muscle and aggravate its trigger points.
- Frozen Shoulder or Adhesive Capsulitis: This term 'frozen shoulder' is an overused label for a vague discomfort and lack of movement. The condition that frequently has no evidence of injury or disease to supporting the diagnosis. The symptoms of a subscapularis trigger points are identical to those attributed to frozen shoulder. Which includes shoulder pain coupled with the limited shoulder joint movement possibility. Trigger points are easily diagnosed and treated, and the pain associated with adhesive capsulitis is generally less severe than the pain from active subscapularis trigger points. These conditions both tend to coexist and reinforce each other - the balance between all aspects of the shoulder is vitally important. So what to do? Treat the trigger points first, and then imagine the surprise if the other condition goes away as well.
Treatment Advice for the Subscapularis Trigger Points
Any soft tissue activity should iinclude the assessment of what stage the tissue is at, and where the greatest challenges to the joint are - a neuromuscular assessment.
In the acute stage of extreme pain and 'loss of motion' of frozen shoulder, subscapularis trigger points play the dominant role. If the condition progresses, the pectoralis trigger points will develop as a secondary location. This is followed by trigger point activity in the teres major muscle and the Latissimus dorsi. In clients diagnosed with Adhesive Capsulitis, therapists should be aware of trigger points in the supraspinatus and deltoid muscles as well.