Touch is an important part of human interaction.
Pain is an unpleasant human experience.
Touch conveys meaning that words often cannot.
Pain is often hard, if not impossible to put into words.
It is not surprising that touching people in pain is a common ritual, and it has likely been performed for thousands of years of humanity.
Touching people in pain has now evolved into specialised forms of physical therapy, from massage to manipulation and everything in between. However, what it all boils down to is touch and narrative.
Many therapists, and particularly those who define themselves by what they do (like osteopaths), will be upset to hear that I don’t think manual therapy has to (or can be) very specific to be effective for pain relief.
Manual Therapy is Applied Force
In his excellent book The Science and Practice of Manual Therapy, osteopath and researcher, Dr Eyal Lederman describes the 2 types of force you can apply to a body with your hands, instruments or body:
- Tension forces
- Compression forces
He elaborates that combinations of these two forces can also be applied, yielding resultant forces such as:
- Torsional forces
- Shearing forces
- Bending forces
When you consider the other variables relating to applied force:
- Speed (technically velocity)
- No of cycles
You can then begin to develop different techniques.
Techniques have historically been named in anatomical terms (myofascial release, joint articulation) or by descriptors of what the technique involves or a proposed mechanism (high velocity-low amplitude – HVLA, counterstrain, muscle-energy technique/proprioceptive neuromuscular facilitation).
Clinically, most therapists will say that different techniques (aka different applications of forces) result in different clinical effects and outcomes.
While there is some research to suggest there are different descending modulation pathways that are stimulated with different manual therapy techniques, overall, our current body of knowledge suggests that the effects are non-specific.
The (Non-Specific) Effects of Manual Therapy
Referring back to Lederman’s book, we can describe the effects of manual therapy in 3 main areas:
- Tissue effects, which are primarily local
- Neurological effects (yes, the nervous system is tissue, but this relates to function of the nervous system)
- Psychological effects
You Can’t Change Tissues, Directly
One of the big misnomers surrounding manual therapy is that it directly changes tissues like muscles, ligaments and fascia.
This is not the case – and it doesn’t make biological sense for it to be.
Imagine, if a pair of hands touching you for a few minutes could stretch out your muscles. What would happen to your muscles as you sit down, or sleep?
Manual therapy can possibly stimulate some cellular responses via mechanotransduction.
- Mechanotransduction is the physiological process where cells sense and respond to mechanical loads. It is independent of the nervous system.
- Mechanotherapy is the therapeutic application of force/load, used to differentitate between homeostatic mechanotransduction.
A 2012 study, Massage therapy attenuates inflammatory signaling after exercise-induced muscle damage, demonstrated this.
While it was quite a small study, with only 11 participants, it shed light on some cellular effects as a result of massage.
The researchers induced muscle fatigue/damage via exercise (stationary cycling) and then massaged one thigh and used the other as a control.
They found that massage activated the mechanotransduction signaling pathways:
- Focal adhesion kinase (FAK)
- Extracellular signal-related kinase 1/2 (ERK1/2)
- Potentiated mitochondrial biogenesis signaling [nuclear peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α)
- Mitgated the rise in nuclear factor κB (NFκB) nuclear accumulation
However, whether at all this is clinically relevant remains to be seen. It is one small study, and most other studies demonstrate a very small effect as well.
What is relevant, is that there is a benefit to tissue repair, particularly in the first 2 weeks after injury from harmonic articulation. This is outlined further in Lederman’s text, but considering that pain often leads to decreased use of tissues, this should be considered as a potential therapeutic option.
So it is fair to say that tissue effects, via mechanotransduction are not relevant to the clinical outcomes resulting from manual therapy.
In part, this is because of the way force is distributed by the body.
The Frictionless Skin-Fascia Interface
Between the skin/subcutaneous fascia exists a frictionless interface. That is, the skin will slide over the fascia below it. Think about this, if this didn’t happen, you could pull your subcutaneous tissues around (this would not be good).
As a result, only force applied perpendicular to bone affects bone – tangential force is dissipated.
This knowledge has implications for manual therapy: can you really shear a fibula or radius? What about a vertebrae?
It’s not possible.
Again, thank goodness.
The most likely effect of manual therapy on pain seems to be facilitating “the drug cabinet in the brain” by descending modulation.
Descending modulation is an important biological process that is protective of us in times of threat, but also helpful in managing pain.
It is known that manual therapy, and even touch can cause the brain to release inhibitory neurotransmitters that modulate pain, most likely at the spinal cord level.
As mentioned above, different types of manual therapy seem to evoke slightly different modulation responses.
Psycho(social) Effects of Touch
Touch is the most important sense we have. Without it, we cannot entirely feel pleasure or pain – we are less than human. – David J. Linden
Psychological effects have some crossover with neurological effects, and tend to evoke:
- Descending modulation
- ANS changes
- Pleasant feelings (positive affect)
People can discern meaning from touch – thus can create therapeutic context with touch.
Think about this, if you caress a loved one, versus firmly grab them around the forearm, does this evoke different thoughts and feelings?
In their paper, The Skin As A Social Organ, the authors argue
However, because the skin is the site of events and processes crucial to the way we think about, feel about, and interact with one another, touch can mediate social perceptions in various ways.
The authors cite 3 mechanisms by which the skin can convey social meaning:
- Through affiliative behavior and communication
- Via affective processing in skin-brain pathways
- As a basis for intersubjective representation
I have never heard this described in any manual therapy course, or through my years of university study, yet it is arguably a bigger factor than mobilising joints or stretching muscles.
The Devil Is In The Dosage
There is scant (read: no) good research on dosage for manual therapy.
Practically, dosage is often constrained by patient/practitioner availability and resources (time, money etc).
Within a session, we can do more manual therapy or less. That much is obvious. However, it is hard to prescribe a dosage for intensity, unlike say, exercise.
That is because, as discussed above, the effects of manual therapy do not rely on mechanical stimulation, but rather contextual facilitation, affective change and possibly (probably) expectation.
So a simple way to gauge the response to manual therapy for dosage reasons is:
In other words, if you can gauge a response (within session changes) and measure the adaptation (between session changes) you can reverse engineer the dosage.
Within Session Changes: What to Look For
The responses we are looking for are often subtle, and if missed, can easily lead to overstimulus.
These are (thanks to Barrett Dorko for a couple of these):
- Softening: a subjective feeling from either patient or practitioner of the tissues softening
- Warmth: a noticeable increase in superficial warmth, typically explained as an increase in cutaneous blood flow
- Movement: this is often spontaneous and effortless (think of a person “adjusting” themselves on the treatment table), but it can also be improved movement based on pre/post clinical assessment.
It is important to realise that within session improvements do not suggest resolution, only that there as been a response to the implied stimulus.
Is It Effective Though?
None of this matters if manual therapy isn’t clinically effective.
Here’s the rub (pun not intended): there is low quality evidence to suggest manual therapy can help certain conditions, while there is high(er) quality evidence that shows a smaller effect.
There is evidence (of varying quality) to suggest manual therapy can also influence the following processes:
- Affects ANS
- Affects tissue tone and ROM
- Affects lymphatic system
- Affects immune system
- Affects haemodynamics
- Descending modulation
Hence I favour a process based approach over a condition based approach to clinical reasoning.
This means that you aim to influence processes that are involved in the patient’s presenting complaint.
Putting It Altogether
In order for manual therapy to have a positive clinical effect, we have to apply the right dosage. In practice, underdosing is preferable to overdosing, as you can always do more, but you cannot take away work that has been performed.
We also know that manual therapy is non-specific, but different techniques potentially effect different descending modulation pathways. With this in mind, using a variety of forces (tension, compression, twisting etc) with a variety of variables (direction, duration, magnitude, frequency etc) will provide a hedge of sorts when an individual’s response and preferences are not fully known or understood. This can be modified over time as the practitioner-patient relationship develops.
Finally, we know that we can’t affect tissues, but we can affect processes, so again, as a hedge of sorts, it is preferable to treat a large proportion of the physical body over a localised approach. The exception to this is harmonic style techniques in the early stages of injury to enhance repair.
Two quotes govern my thinking around manual therapy for the treatment of pain:
When pain is the primary complaint, treatment of pain should be primary. – Barrett Dorko, PT
And the second:
Manual therapy is optional, but it can be optimal (for the treatment of pain). – Diane Jacobs, physiotherapist
If we understand the likely processes involved in manual therapy, and we acknowledge what we don’t know, along with what we know with a high degree of certainty is unlikely, then I can see well explained and well executed manual therapy continuing to play a role in therapy for many years to come.
If we continue to “treat anatomy” in relation to pain, then over time, funding from health systems and insurers will dry up, as the link between anatomy and pain is tenuous at best.
Finally, we have to give patients a voice. If patients determine they receive a benefit that is meaningful to them, we cannot discount that, as long as they understand the nature of the benefit (i.e. often transient and part of a bigger picture approach to health and pain management).