I recently read a post about how manual therapy does not really require "skill." Initially, I found the post somewhat infuriating as I have been making my way through a residency that is heavy in manual therapy. However, after reading some of the articles referenced on the post and after following The Manual Therapist blog for awhile, I realized that the popular theories behind the effectiveness of manual therapy may not be as accurate as I thought. That doesn't mean manual therapy isn't effective, but that it may have a different mechanism. This inspired me to do a review on the literature from this alternative perspective.
Soft Tissue Mobilization
There are various soft tissue techniques (Graston Technique, ASTYM, trigger point release, etc.) that are based on the theory of collagen deformation. Although largely based on theoretical and mathematical models, studies have shown that it requires greater forces than human ability can apply to deform fascial tissue even 1% (Chaudhry et al, 2008). This may be difficult to accept for some therapists, as many will claim feeling a tissue "release" with overpressure. However, it has been shown that the manual pressure applied by therapists actually stimulates mechanical receptors in the tissue, which lowers sympathetic tone in the tissue and a "release" of the adhesion (Schleip, 2003). Again, that doesn't mean the techniques performed don't work, just that they don't work based on the theorized mechanism. This is advantageous to understand as it may alter our technique choice and how we implement it. I have training in IASTM (Instrument-Assisted Soft Tissue Mobilization) based on this neurological effect. Why perform a technique that may injure a patient via bruising, or worse, when we can be as, or more, effective doing something less invasive?
Stretching is a treatment technique that has been a foundation of physical therapy for decades. Quite a bit of research has been done on the topic. In school, the standard practice is that 30 seconds of static stretching is required to get plastic deformation on tissues. But does this actually occur? Without a doubt, it would appear that people can "stretch" their muscles further after a designed stretching program. There are many theories as to how this happens: viscoelastic deformation, plastic deformation of connective tissues, increased sarcomeres in series, and neuromuscular relaxation (Weppler & Magnusson, 2010). However, there appears to be insufficient evidence for each of these areas. With regards to the viscoelastic model, studies have shown that the changes that do occur are small and have short duration. No evidence has been found for true plastic (or permanent) deformation of muscle tissue via stretching. Many report that prolonged immobilization results in altered numbers of sarcomeres in series - on a stretch they increase in series and in a contracted position they decrease. These studies have been inappropriately applied to static stretches. In fact, it was found that after removal of the immobilization, the sarcomere number go back to the original amount. What is often ignored is that these studies are performed on animal muscle tissue by themselves. We do not truly know how sarcomere react in series to stretching in conjunction with tendons, other fascial structures, skin, etc. This is an important component as that is how the body truly functions and we cannot separate out muscle from those other structures when stretching. The neuromuscular relaxation theory is based on altering the stretch reflex to allow a muscle to relax (and thus "stretch") further. Studies have been unable to prove this theory valid with no alterations in the EMG activity of the stretched muscles. In fact, regular stretching was shown to have no significant change on joint mobility, pain, spasticity, or functional limitations in those with neurological conditions (Katalinic et al, 2011). An alternative theory that is presented is changes in muscle length are actually due to a change in perception of stretch (Weppler & Magnusson, 2010). There has been limited evidence to support this theory, but it is based upon a study that showed an increase in end-range joint angle with no change in applied force and no permanent change in length (no plastic deformation). The end-range joint position was based upon subjective sensation of a "stretch."
Mobilization and Manipulation
With my residency training, a significant amount of time and effort was placed into trying to isolate and locate a specific hypomobile segment to treat. Needless to say, I became somewhat defensive when I heard there was little support for being so specific. Studies have shown that there is no greater benefit for manipulation of a targeted (hypomobile/painful accessory motion based on examiner assessment) joint manipulation compared to a non-specific joint manipulation (Chiradejnant et al, 2003) (Aquino et al, 2009) (Schomacher 2009) (Nyberg & Russell Smith, 2013). However, each of the studies had limitations: chronic pain, potential patient population bias, etc. These findings lend support to the clinical prediction rules that are not specific in nature and may suggest another sign of potential neurological impact and basis for our manual therapy techniques. What exactly happens with a manipulation is difficult to understand. I remember being taught that the cavitation heard is a result of the fluid in the joint capsule quickly evaporating due to the expanded volume of the capsule (and fixed fluid) as a result of the thrust. Whether or not these capsular changes are maintained over time, or even occur, is lacking in evidence.
That doesn't mean manual therapy isn't useful. Clinical predictions rules have been developed for patients with neck or low back pain that would benefit from a manipulation (Cleland et al, 2007) (Puentedura et al, 2012). There are those that suggest a mobilization can be as effective as a manipulation, with the only benefit being a manipulaiton can accomplish the same result in less time, but some research shows manipulations may actually be superior. Manipulations have been shown to have a greater effect on ROM, pain, disability and muscle performance compared to non-thrust mobilizations (Dunning JR et al, 2010). Manipulations to the thoracic spine were shown to have a more significant effect on neck pain than mobilizations. (Cleland et al, 2007). With the risk for injury to various structures in the cervical spine, many are hesitant to even consider a grade V thrust to the area. The only reason it is worth considering is that cervical manipulations had a greater effect than thoracic manipulations on neck pain (Puentedura et al, 2011). It is worth noting that with any manipulation or mobilization, we must carefully screen our patients for contraindications such as osteoporosis, RA, chronic steroid use, etc.
In summary, the results we get from our manual techniques may not be due to the theories on which we were trained, but that does not mean it isn't skilled. A level of clinical reasoning is beneficial to understanding how and why manual therapy treatments can be applied. Manipulations and mobilizations may not be as specific as we thought, but a certain level of training typically is required to be able to perform. But why do those changes occur? While the current popular theories of various manual therapy techniques may have the positive impact we desired, they may not be accurate. This is worth discussion and further investigation to make our treatments as effective as possible. Why injure our patients with certain manual therapy treatments when this can be avoided? Some evidence suggests that we may alter neuromuscular perception by activating mechanoreceptors. While this is not concrete evidence, it may be worthy a topic of research in the future and may play a role in how we can be most effective with our treatments.
Aquino RL, Caires PM, Furtado FC, Loureiro AV, Ferreira PH, & Ferreira ML. (2009). Applying Joint Mobilization at Different Cervical Vertebral Levels Does Not Influence Immediate Pain Reduction in Patients with Chronic Neck Pain: A Randomized Clinical Trial. Journal of Manual & Manipulative Therapy. 2009 April;17(2): 95-100.
Chaudhry H, Schleip R, Ji Z, Bukiet B, Maney M, & Findley T. (2008). Three-Dimensional Mathematical Model for Deformation of Human Fasciae in Manual Therapy. Journal of American Osteopathic Medicine. 2008 Aug; 108(8):379-390.
Chiradejnant A, Maher CG, Latimer J, & Stepkovitch N. (2003). Efficacy of "Therapist-Selected" Versus "Randomly-Selected" Mobilisation Techniques for the Treatment of Low Back Pain: A Randomised Controlled Trial. Australian Journal of Physiotherapy. 2003; 49(4):233-241.
Cleland JA, Childs JD, Fritz JM, Whitman JM, & Eberhart SL. (2007). Development of a Clinical Prediction Rule for Guiding Treatment of a Subgroup of Patients with Neck Pain: Use of Thoracic Spine Manipulation, Exercise, and Patient Education. Physical Therapy. 2007 January;87(1):9-23.
Cleland JA, Glynn P, , Whitman JM, Eberhart SL, MacDonald C, & Childs JD. (2007). Short-Term Effects of Thrust Versus Non-Thrust Mobilization/Manipulation Directed at the Thoracic Spine in Patients with Neck Pain: A Randomized Clinical Trial. Physical Therapy. 2007 April;87(4):431-440.
Dunning JR, Cleland JA, Waldrop MA, Arnot C, Young I, Turner M, & Sigurdsson G. (2010). Upper Cervical and Upper Thoracic Thrust Manipulation vs Non-Thrust Mobilization in Patients with Mechanical Neck Pain: A Randomized Controlled Trial. Journal of Manual & Manipulative Therapy. 2010 December;18(4):175-180.
Katalinic OM, Harvey LA, & Herbert RD. (2011). Effectiveness of Stretch in the Treatment and Prevention of Contractures in People with Neurological Conditions: A Systematic Review. Physical Therapy. 2011. Jan;91(1): 11-24.
Nyberg RE & Russell Smith A. (2013). The Science of Spinal Motion Palpation: A Review and Update with Implications for Assessment and Intervention. Journal of Manual & Manipulative Therapy. 2013 Aug;21(3):160-167.
Puentedura EJ, Cleland JA, Landers MR, Mintken P, Louw A, & Fernandez-de-las-penas C. (2012). Development of a Clinical Prediction Rule to Identify Patients with Neck Pain Likely to Benefit from Thrust Joint Manipulation to the Cervical Spine. JOSPT. 2012 July;42(7):577-592.
Puentedura EJ, Landers MR, Cleland JA, Mintken P, Huijbregts P, & Fernandez-de-las-penas C. (2011). Thoracic Spine Thrust Manipulation Versus Cervical Spine Thrust Manipulation in Patients with Acute Neck Pain: A Randomized Clinical Trial. JOSPT. 2011 April;41(4).
Schleip R. (2003). Fascial Plasticity - A New Neurobiological Explanation: Part 1. Journal of Bodywork and Movement Therapies. 2003 Jan;7(1):11-19.
Schomacher J. (2009). The Effect of an Analgesic Mobilization Technique when Applied at Symptomatic or Asymptomatic Levels of the Cervical Spine in Subjects with Neck Pain: A Randomized Controlled Trial. Journal of Manual & Manipulative Therapy. 2009 April;17(2): 101-108.
Weppler CH & Magnusson SP. (2010). Increasing Muscle Extensibility: A Matter of Increasing Length or Modifying Sensation? Physical Therapy. 2010 March;90(3): 438-449.