The Mechanistic-based Approach for Manual Therapies

This month, the Massage Therapy Foundation Writing Group takes a look at a review of mechanistic approaches to manual therapy. The premise of the clinical commentary titled Unraveling the Mechanisms of Manual Therapy: Modeling an Approach, written by Bialosky et al, is that there is no one approach to manual therapy (MT) to treat various conditions. There are many factors to consider in manual therapy treatment. Identifying the “specific and nonspecific factors related to the intervention, the patient, the provider, and the environment in which the intervention is provided” is key.

Having a theoretical model could be beneficial to inform practice and research. Thus, the authors devel-oped a theoretical model related to the inhibition of pain. According to the commentary, “The model postulates that the mechanical stimulus from an MT intervention results in neurophysiological re-sponses within the peripheral and central nervous systems responsible for pain inhibition.”

This model can be applied to a variety of MT approaches, such as joint mobilization, massage, and neurodynamic interventions. For researchers, consideration could be given to various mechanisms when designing studies and recognize the possibility of alternative explanations to findings if the study does not account for competing mechanisms. These could include biomechanical effects, peripherally mediated effects, spinal cord-mediated effects, and supraspinally mediated effects.

Being able to evaluate the nervous system responses in humans to MT in mechanistic studies is a challenge. The model presented by the authors considers responses serving as behavioral correlates, such as sympathetic nervous system responses represented by changes in skin blood flow or changes in the flexor withdrawal reflex which may represent a spinal cord-mediated response. While pre/post random-ized controlled trials provide evidence of neurophysiological responses to MT, they are not designed to determine the factors of clinical improvement. Linking these responses to symptoms and clinical out-comes through complex study designs should be considered by future researchers.

Evaluating immediate responses has its limitations since similar findings have been found with numer-ous interventions without being linked to long-term clinical outcomes. Additionally, individuals have varying pain thresholds. Thus, the authors propose “pain modulatory profiles may be useful in identify-ing more homogeneous groups of patients.” Identifying the type of pain or pain threshold and applying the appropriate MT mechanism may lead to longer term outcomes. Having a mechanistic model to use based on research which takes these variables into consideration may inform practice more appropri-ately.

The authors present a wide range of limitations to current MT research based on variations in patients, pain thresholds, MT mechanisms, and MT force. They also propose a model using a zone approach:

Zone 1 representing the provider, mechanical force, and targeted tissue

Zone 2 representing patient nervous system responses

 Zone 3 representing clinical outcomes

The bottom line of this commentary is summarized by the authors in the following statement: “We believe that a continued emphasis of the model of the mechanisms of MT in pain inhibition is warranted, because (1) other domains are not mechanistic, precluding a similar approach to study; and (2) pain in-hibition is an important precursor to the other domains. However, mechanistic studies should be designed to link MT related pain inhibition to core outcome domains that are valued from a patient per-spective.” The authors conclude that “greater consideration of pain modulatory capacity, as determined by dynamic measures of psychophysical testing, consideration of neurophysiological responses to MT, and studies better designed to account for potential mediators and moderators of treatment outcomes, will better inform knowledge of this important topic.”

This article has important implications for research and practice. For researchers, is it possible to design mechanistic studies for pain that start with the most homogenous group of subjects, especially those studies related to pain thresholds, with identical MT force and identical practitioner biases towards re-sults in order to truly measure outcomes? For massage therapists, would having a model for practice be beneficial? Is development of a ‘one size fits all’ approach possible for those who present with specific pain?

Call out – Do you have an interest in research principles, practices and studies? Make plans to attend this year’s Massage Therapy Foundation’s International Massage Therapy Research Conference in Alexandria VA from May 9-10th. Visit http://massagetherapyfoundation.org/imtrc-2019/ to register today!

Editor’s Note: The preceding research synopsis is authored by volunteers from MTF’s Writing Workgroup.