How does orthopaedic manual physical therapy work? The available evidence strongly suggests that it is by a neurophysiologic affect. (1) The differences of effect between mobilization and manipulation techniques have not been consistent, or clear. The specific neurophysiologic mechanism and where it is occurring is also not well understood.
Fisher (2016) The effect of velocity of joint mobilization on corticospinal excitability in individuals with history of ankle sprain in the most recent JOSPT may be an interesting step towards better understanding the neurophysiologic effects of OMPT. The researchers, led by Beth Fisher, included AAOMPT founding fellow Kornelia Kulig.
The population studied was individuals with recurrent ankle sprains. Examined were the pre and post talocrural intervention measures of mobility, functional balance, and neurophysiologic change between three groups. Those groups were a 30 second traction mobilization, a gapping manipulation, and a control group.
Disappointingly, mobility and function remained unchanged across the groups. The study proposed several possibilities to explain this result, BUT that wasn’t the interesting part.
Previous research involving stretching, manipulation, or mobilization has shown the neurophysiologic change of a short term decrease in the H-reflex response (that’s the Hoffman’s reflex, not to be confused with the Hoffman’s sign). The Hoffman’s reflex is measured by EMG and demonstrates a neurophysiologic change at the level of the spinal cord. In this study surface EMGs were combined with transcranial magnetic stimulation (TMS). Never heard of it? Well I had to look this one up too! It is a fairly new technique used for a growing number of diagnostic and treatment purposes. In this case it was to measure activity between the motor cortex and select targets muscles. These neurophysiologic measurements were made both at rest and during sub-maximal activity.
The manipulation group showed a significant increase in corticospinal activity, not shown in the other groups. In the 30 second traction mobilization group, corticospinal activity was decreased, which is consistent with H Reflex observations of OMPT. Perhaps this is reflective of different joint receptors being triggered with sustained traction vs manipulation as Wyke’s (2, 3) articular neurology work would suggest. The maximal evoked potential of one of the muscles studied (tibialis anterior) was also increased specifically in the manipulation group. Other muscles curiously were unaffected.
The facilitation of activity in the cortico-spinal motor tracts shown with the manipulation group is similar to activity observed during learning new motor tasks( 4, 5). This study is suggesting that manipulation may specifically potentiate motor learning, within the brain.
Consistent with other studies, these neurophysiologic effects are of limited duration to about 30 minutes. Previous studies (6-10) support that OMPT alone does not demonstrate significant improvements. For that to occur, exercise or muscular re-education is an essential component. Remember that after any OMPT intervention, motor learning is the key to making a real and durable difference. If they leave the clinic before motor learning is initiated, then there goes your window to seal the deal with post-OMPT optimized motor learning. It appears that with OMPT, and perhaps manipulation specifically, the entire nervous system may be set up to learn something new. When you use manipulation, remember to act on your opportunity and re-educate!
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