Laws of Physiology

Laws of Physiology

Studying the laws of physiology can give you a deeper understanding of what you are doing when you are working with clients. 

A law of physiology (as found in Taber’s medical dictionary) is a scientific principle that is uniformly true for a

whole class of natural physiological occurrences.  

Law of Facilitation
When an impulse has passed through a certain set of neurons to the exclusion of others, it will tend to take the same course on a future occasion and each time it traverses this path the resistance will be less.

Applications:
The nervous system conditions itself to find the path of least resistance. The body produces habitual patterns when a neural pathway is activated.  The law of facilitation answers the question, “why does it hurt in the same place every time?”
Old injuries tend to get re-aggravated with less stimulus.  Pain patterns tend to become set patterns in the body.  Once an area is injured or compromised you are more likely to have the injury occur again with less stimulation.  It will also take less time to heal itself again.
Also the more you get massage, the easier it is to relax.

Hiltons Law
A nerve trunk that supplies a joint also supplies the muscles of the joint and the skin over the attachments of such muscles. 

Applications:
If an injury occurs it may be difficult to determine if the pain is coming from the skin, muscle or joint. Stimulation of all areas in turn affects each part. Palpation and other tools are needed to assess the area.
This is one of the reasons why working superficially on the body will often create a deeper release of tissues.

Arndt-Schultz Law
Weak stimuli activate physiological processes: very strong stimuli inhibit physiological responses.

Applications:
Use gentler methods that are slower of less stimulating to activate physiological responses.  Doing deep tissue slowly and gently is more effective than using force.
Tissue that is gently agitated will heal faster than tissue that is left alone.  Weak stimulus activates tissue growth and wound healing.
Triggerpoints can give off strong impulses that can turn off other processes in the body. Whiplash injuries can influence the activity of the thyroid gland.
To turn off a response, use stronger stimuli.  To stop pain use cross fiber friction applied for a few minutes.

Davis’ Law
If muscle ends are brought closer together, then the pull of tonus is increased, thereby shortening the muscle which may even cause hypertrophy.  If muscle ends are separated beyond normal, then tonus is lessened or lost, thereby weakening the muscle.  If soft tissue is placed under unremitting tension, the tissue will elongate by  adding more material.

Applications:
If you don’t use it you lose it!

This can be seen in muscle imbalances where one ser of hypertonic muscles have shortened and become hypertrophied while the antagonists have weakened in response to their being stretched beyond normal.  A person with rounded or forward rolled shoulders will have tight, hypertrophied pec. major and minor muscles while their rhomboids will be weak.

Reciprocal Inhibition
When the agonist is firing and the affected joint moves, the antagonist group will be inhibited.  This is the basis for coordinated movements of the musculo-skeletal system.

Application:
This can be used to treat cramps or hypertonic muscles.
This is the basis for PNF -Proprioceptive neuromuscular facilitation.

All or none
The weakest stimuli capable of initiating a response, triggers an impulse that is transmitted along the entire neuron or muscle fiber, producing maximum strength response in cardiac and skeletal muscles and nerves.

Application:
A little can go a long way to produce a response.

In muscle contraction, all fibers of the muscle must contract for optimal functioning.  When adhesions and scar tissue form in the muscle, it reduces the effectiveness of the muscle.

Law of specificity of nervous energy
Excitation of a receptor always gives rise to the same sensation regardless of the nature of the stimulus.

Application:
It doesn’t matter which method you use to activate a sensory receptor, it will respond in a specific manner.  Technique or modality are not as important as the simple process of activating the sensory receptor in some manner in order to achieve a response.

Weber’s law

The increase in stimulus necessary to produce the smallest perceptible increase in sensation bears a constant ratio to the strength of the stimulus already acting.

Application:
Just a little bit more will change the perception.  For an application of massage to alter or change a sensory perception, the intensity of the application must match and barely exceed the existing sensation.  To overcome a perception of cold you would need to apply a compress which is at minimum one degree warmer than the areas temperature to create a sensation of warmth.

Pfluegger’s Laws- general laws that explain the body’s transition from an acute pain syndrome to a chronic pain syndrome.  A trauma to one part of the body, if left untreated will progress into a chronic full body condition.

Law of Unilaterality
If mild irritation is applied to one or more sensory nerves, the movement will take place usually on one side only, on the side that has been irritated.
Application: The body responds to trauma initially at the site of the injury.  Light stimulation remains fairly localized.  If a client experiences mild irritation it will likely effect the localized area on the side of the body in which the irritation has occurred.

Law of Symmetry:
If the stimulation is sufficiently increased, motor reaction is manifested not only by the irritated side, but also in similar muscles on the opposite side of the body.
Application:  If trauma is great enough, pain may be experienced on the opposite side of the actual injury.  By using increasing levels of massage intensity, a bilateral effect can be created even if massaging only one side of the body.  By massaging the unaffected side, the painful areas can be addressed without direct massage work.  This leads to the idea that applications of massage should take into account the whole body and that massaging the associated areas especially on the opposite side of the body will increase the overall affect of the massage.

Law of Intensity:
Reflex movements are more intense on the side of irritation and less strong on the opposite side.
Application: similar to the law of symmetry.  

Law of Radiation
If the excitation continues to increase, it is propagated upward and reactions take place through centrifugal nerves coming from the cord segments higher up.
Application:  Simulation will move up the spinal column and trigger reactions in the corresponding body areas innervated by those nerve segments. There may be spasming and pain above the actual site of the injury to protect the injured area.  (Muscle guarding)

Law of Generalization:
When the irritation becomes very intense, it is propagated in the medulla oblongata, which becomes a focus from which stimuli radiate to all parts of the cord, causing a general contraction of all muscles of the body.
Application: Very intense massage application can trigger whole body muscular contractions (massive muscle guarding). This is what trauma does to the body creating intense, generalized whole body muscular contraction.

Law of conservation of energy
Energy is constant: it is neither created or destroyed but only transformed from one form or another.
Applications:  The energy that is a result of a massage has been transformed or released within your client.
When a traumatic event such as a motor vehicle accident occurs, the energy of the force of the car is absorbed by the body.  Healing is achieved by releasing this energy from the body.

Murphy’s law
If something can go wrong it will.
Application : Never assume that something will never happen to you.  This is especially true when looking at issues that arise in the therapeutic relationship.  Be careful of dual relationships, power differences and boundaries.

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