Pain due to motor error or motor error due to pain?

[Diane]

Not sure yet how this will fit in, but I wanted to start a thread on my favorite topic, skin, cutaneous input, and thought I'd post this abstract here:
http://www.ncbi.nlm.nih.gov/entrez/q..._uids=14565854

BMC Musculoskelet Disord. 2003 Oct 17;4(1):23.

Postural stability is altered by the stimulation of pain but not warm receptors in humans.

Blouin JS, Corbeil P, Teasdale N.

Universite Laval, Division de kinesiologie, Faculte de Medecine, Quebec, Canada. jsblouin@kin.msp.ulaval.ca

BACKGROUND: It is now recognized that large diameter myelinated afferents provide the primary source of lower limb proprioceptive information for maintaining an upright standing position. Small diameter afferents transmitting noxious stimuli, however, can also influence motor behaviors. Despite the possible influence of pain on motor behaviors, the effects of pain on the postural control system have not been well documented. METHODS: Two cutaneous heat stimulations (experiment 1: non-noxious 40 degrees C; experiment 2: noxious 45 degrees C) were applied bilaterally on the calves of the subject with two thermal grills to stimulate A delta and C warm receptors and nociceptors in order to examine their effects on postural stability. The non-noxious stimulation induced a gentle sensation of warmth and the noxious stimulation induced a perception of heat pain (visual analogue scores of 0 and 46 mm, respectively). For both experiments, ten healthy young adults were tested with and without heat stimulations of the lower limbs while standing upright on a force platform with eyes open, eyes closed and eyes closed with tendon co-vibration of tibialis anterior and triceps surae muscles. The center of pressure displacements were analyzed to examine how both stimulations affected the regulation of quiet standing and if the effects were exacerbated when vision was removed or ankle proprioception perturbed. RESULTS: The stimulation of the warm receptors (40 degrees C) did not induce any postural deterioration. With pain (45 degrees C), subjects showed a significant increase in standard deviation, range and mean velocity of postural oscillations as well as standard deviation of the center of pressure velocity. The effects of heat pain were exacerbated when subjects had both their eyes closed and ankle tendons vibrated (increased standard deviation of the center of pressure velocity and mean velocity of the center of pressure). CONCLUSIONS: A non-noxious stimulation (40 degrees C) of the small diameter afferents is not a sufficiently intense sensory stimulation to alter the control of posture. A painful stimulation (45 degrees C) of the skin thermoreceptors, however, yielded a deterioration of the postural control system. The observed deteriorating effects of the combined stimulation of nociceptors and Ia afferents (when ankle tendons were vibrated) could result from the convergence of these afferents at the spinal level. This could certainly lead to the hypothesis that individuals suffering from lower limb pain present alterations of the postural control mechanisms; especially populations already at risk of falling (for example, frail elderly) or populations suffering from concomitant lower limb pain and sensory deficits (for example, diabetic polyneuropathy).
Publication Types:
* Clinical Trial
PMID: 14565854 [PubMed - indexed for MEDLINE]

Sounds to me like the article is saying that motor planning depends on skin proprioception, and that motor planning can be messed about by pain. And that old lower leg skin is less accurate at assisting motor planning. Makes me want to teach foot and ankle exercises to all patients, and to do skin techniques on every ankle regardless of where pain might be located in the body.. and kinesio tape all older legs and feet and ankles..

Sounds to me to be a bit backwards from the belief system we usually succumb to which more less implies that we can exercise our way out of pain states or any sort. (I've never thought that was really true, having experienced pain states myself and having needed skin contact of some sort to remedy the problem.)

Having said that, however, I realize there is a small percentage of patients who will get worse if you touch them. And I think that this minority of patients do require the movement-to-fix-pain strategy, first... but, to further complicate matters, I've seen people who have two sorts of pain states at the same time, and who feel quite differently about each one. And these states have different handling requirements. What a crap shoot!

Anyone have any thoughts/comments?
Diane

[nari]

Diane,

I don't know what to think about this article - there are so many variables in patients: those who respond well to tactile handling, those who hate it, those who respond very well all round to simple exercise like sit-->stand--> sit and other basic movements, and those who respond best to passive machines. How one determines which direction to take takes some time.
Once again, it may fall to the therapist's personal clinical reasoning and knowledge.

Then it has been shown that for the chronic pain of 'frozen shoulder', the poor patient is actually made worse and recovery is delayed, if there is regular physio intervention. (I can post the reference - cannot seem to transmit anything else!!) Which suggests strongly that we certainly can delay recovery with tactile work.

Interesting that 45 degrees is not all that hot - I wonder how they chose that figure, rather than 50+. As for the implications for the elderly and frail...they are enormous. Here we have two levels of Falls clinics, where PTs do full assessments of persons at risk: some have pain, some do not.
Would be good to follow this through with the clinics.


Nari

[Diane]

Hi Nari,
Thanks for your thoughtful, as always, reply.
I think the biggest deficit we have as PTs, if we take studies like this to heart, is that we aren't usually taught what to do with skin. Our training takes us straight past it/through it, into joints and muscles. Chiro training takes chiros into the spine...did they ever learn to care about anything else?
I learned how to handle skin much later, way post graduate, from the D.O. branch of the practitioner family. And sadly, even though traditional skin handling techniques from the osteopathic side of life are superb, ...even they don't consider skin much. They are using a focal length that is deep also, and think they are affecting head sutures, joints, muscles, viscera, etc. And we all know they pay a price for thinking that is what they are doing.
But the truth is... if the skin is treated well, all that other stuff can be elicited, presumably by reflex.
To give Barrett Dorko his due, he is the only clinician whose focal length has stayed on the skin and the nervous system within it, and hasn't wandered below into other tissues.

About frozen shoulders, I agree that "physiotherapy" makes them "worse" if the joint is the target. (Shudder!) But if the shoulder is ignored, the pelvis is mopped up, the lat is "handled" (skin stretched) is a comfortable sidely position, if the axilla skin is stretched gently while the arm is allowed to rest quietly, if the skin over pec/anterior shoulder is stretched gently by pulling the upper arm skin downward toward the elbow in supine lying, arm supported and resting.. it is amazing how a great number of those so-called frozen shoulders thaw on the spot. No, I don't have a study on that. Just me, working on people.
Cheers,
Diane

[bernard]

Hi Somasimplers,

I will elaborate later but my actual opinion is that pain is an output and it is more sensed to think it is a result of a motor error (with the skin inputs).

[Diane]

I look forward to your thoughts Bernard. I think my thoughts are in pretty good alignment with yours.
Diane

[bernard]

Conclusion:

Muscle is a (sensitive) component that helps brain to discover the World. It helps skin to be in front of the scene.

[bernard]

Hi Somasimplers,

http://www.accampbell.uklinux.net/bo...ws/r/wall.html

There is no such thing as a pure pain; pain is always part of a motor response, or at least a planned motor response (changes occur in the motor system of the brain even when no overt muscular contractions ensue). This is a radical but illuminating idea, with far-reaching implications for those of us who are involved in trying to relieve pain in patients. It also has implications for philosophical problems such as the nature of consciousness itself.

Hmmm, I love that one!

[bernard]

Diane,

Coming back to the paper you cited, I have a problem with their hypothesis?

1/ It is known that heat is relied to brain by small C fibers, but normal heat (<43°C) is linked to a kind of neurons and there is other ones that transmit noxious events when temperature is > 43°C.
2/ The first experiment activate two kind of fibres (simplified).
3/ The second experiment activate Three kind of fibres.
4/ The second contains a noxious stimilus and it is transmitted in spinal cord and felt as unpleasant in such experience!

[bernard]

http://www.ualberta.ca/~aprochaz/res...y_of_pain.html

The lack of pain effect on the excitability of the spinal motoneuronal pool and the cortico-spinalpathways leads us to the conclusion that the altered voluntary movement patterns characteristically seen during muscle pain result from altered input to the motor cortex...

It is my view!