Many authors & researchers claim & have demonstrated that therapeutic effects of manual therapy are due to pain modeling via sensory inputs through their well designed researches. But many clinicians believe that manual therapy lead to subtle bony adjustments which leads to it’s therapeutic effects. However, it is not well demonstrated that adjustments occurs in such cases.
This following paper by Keller & colleagues is one among the many papers that indicates but do not clearly demonstrate the potential mechanical adjustments by manual therapy. The experiment was carried out on a replica (model) of the spine & model validity was determined which showed good agreement with in vivo human studies.
This study reveals following:
1. Quasi-static and low-frequency (<2.0 Hz) forces at L3 produced L3 segmental and L3-L4 inter-segmental displacements up to 8.1 mm and 3.0 mm, respectively.
2. Impulsive forces (Such as used in HVLA manipulative techniques) produced much lower segmental displacements in comparison to static and oscillatory forces.
3. Differences in inter-segmental displacements resulting from impulsive, static, and oscillatory forces were much less remarkable (all techniques may result in similar outcomes!!!).
The latter suggests that intersegmental motions produced by spinal manipulation may play a prominent role in eliciting therapeutic responses.
Keller TS et al; J Manipulative Physiol Ther. 2002 Oct; 25(8):485-96.