As a therapist who works within the fields of pain, movement, energy and digestion I have seen my share of pain and muscle dysfunction in clients. As my exposure to these situations increase, I realise more than ever, that the muscles are very rarely the problem. Specific muscle dysfunction usually boils down to spindle cell
dysfunction and notably Nuclear Bag Fibres (NBF) and Nuclear chain Fibres (NCF). The primary roles of these structures are related to stretch and contraction of muscle function. There can be other factors involving neuro transmitters, involved in nocicpetion such as glutamate, utilised in the withdrawal reflex and often referred to as first pain, (also known as Neospinalthalamic tract located in the Anterolateral system or ALS) and lasting, less than a tenth of a second. Problems can arise when the following pain pathway, called second pain (or Paleospinalthalmic tract also part of the ALS) has problematic feedback with first pain, this is mediated by Bradykinin.
Further complexities arise with serotonin and other structures associated with pain such as the Amygdala and Peri Aqueductal Gray (PAG) that are beyond the scope of this short blog. However a common, over looked feature of pain, may arise with hypothyroidism .
Low thyroid function can be classified effectively with assessment of a basal temperature test and a reading of between 36.6 and 37 degrees. Most blood tests designed to measure thyroid hormones such as TSH, T3, T4 and others, often do not reflect accurate function of thyroid hormone. This is often due to feedback loops between cellular function and the Pituitary gland. Some of the regular hallmarks of hypothyroidism are poor energy, weight gain, poor sleep, hair thinning, digestive dysfunction (constipation and also alternating loose stools), cold hands and feet and pain. Here's an old blog on thyroid and adrenalin issues.
Another assessment of thyroid function is the Achilles return reflex. When stimulating the myotactic reflex a hammer hits the Achilles tendon stimulating, the dorsi flexors or calf muscles. The response should be a quick return of the foot to it’s resting position but with low thyroid the foot returns slowly. Low thyroid output equals low ATP (Adenosine Tri Phosphate – the energy used by the mitochondria/cells). This low energy state does not allow for optimal contraction and relaxation. This is where we can see specific issues with NCF and NBF’s within the muscle spindle cell.
Muscle tendons and associated ligaments provide a feedback loop via the Golgi Tendon Organs or GTO’s. There’s potential for pre-existing GTO dysfunction to drive muscle dysfunction and vice versa. As far back as the 1960s symptoms associated with muscle disorder from low thyroid were.
* Cramps pain and stiffness
* Myotonoid features.
A well-documented feature of hypothyroidism is muscular hypertrophied calf muscles and despite their size may often test weak to stimulation.
Muscle pain, may indeed not be muscle related, it may be due to many factors, suggested above and these may even be related to hormones and neurotransmitters. Many people often deal with muscle aches and pains by constantly focusing on mobility work but these structures continually return to their pre mobility work status (although this could also be an underlying stability issue). In reality there can be many factors that create dysfunction such as crude touch, vibration, nociception, Golgi, Pacini-pressure related structures and many more. But even after seeing a skilled therapist, these still don’t appear to get better, then addressing the chemical aspects of pain and function might be the next sensible thing to do.
Armour Laboratories. The Thyroid Gland and Clinical Application of Medicinal Thyroid. 1945.
Ramsay I. Thyroid disease and Muscle Dysfunction. William Heinemann Medical Books. 1974.
Purves, D. et al. Medical Neuroscience. 5th Edition. Sinauer Assocates Inc. 2001
Starr, M Hypothyroidism Type II. Mark Starr Trust 2013.