MET Research Paper Critique- SPRING 2008Critique: "The effect of muscle energy technique on hamstring extensibility: the mechanism of altered flexibility" By F. Ballantyne, G. Fryer, P. McLaughlin Published in the Journal of Osteopathic Medicine, 2003; 6(2), pages 59-63by Martin Kingston This article appeared in the newsletter for BodyworkersLondon.com THIS IS A COPY OF THE CRITIQUE HANDED IN TO WESTMINSTER UNIVERSITY 29TH APRIL 2008 - for information to patients showing there is research into the techniques I use, but it is of VERY variable quality! ! Muscle Energy Techniques (MET) are defined according to Chaitow (2006,
page 1) as "osteopathic (originally) manipulation methods that incorporate
precisely directed and controlled, patient initiated, isometric and/or
isotonic contractions, designed to improve musculoskeletal function and
reduce pain". They are characterised by gentle contraction of muscles
(either agonist or antagonist), followed by a relaxation period. MET has evolved separately from Proprioceptive Neuromuscular Facilitation (PNF) Stretching, which has evolved in a physiotherapy setting, and was originally concerned with strengthening neurologically weak muscles, and now focuses on lengthening shortened or tight muscles, and usually involves high intensity active muscular contractions, followed by a active or passive stretching. There is an overlap in some of the techniques used, but it is recognised that Muscle Energy Techniques, by using more gentle contractions, are less likely to induce tissue damage, pain or cramp (Chaitow 2006 page 4). Sandra Yale (in DiGiovanna 1991, referenced by Chaitow 2006 page 6) therefore considers them appropriate for fragile and severely ill patients. The authors for this piece of research, Ballantyne, Fryer and McLaughlin are associated with the School of Biomedical and Health Sciences in Victoria University, Melbourne, which teaches Osteopathy, Chinese Medicine and Paramedic Health Science to degree level. They undertook a piece of research to investigate "the effectivenes of muscle energy technique in increasing passive knee extension and to explore the mechanism behind any observed change" (page 59). These two objectives will be both assessed in this report. Research into manual techniques is timely: practice can vary tremendously, and good research could guide standards in practice. Unfortunately, this research has limited value because the authors are ambiguous in their terminology, which has a knock on effect on results and conclusions. Inadequate Definitions of TermsCrucially, although the authors claim to research muscle energy technique, the process they measured is more akin to the Contract-Relax protocol of PNF stretching. In the title of the study, they identify Muscle Energy Technique in the singular. There are a variety of techniques from different authors, with different objectives. Stemming from Ruddy's "rapid rhythmic resistivie duction" in the mid 20th century, which inspired Fred Mitchell Snr and Jnr (Michell et al 1979, reference by Chaitow 2006 page 6) to develop methods which now commonly are called Muscle Energy Techniques. Since then, Janda (1993), Chapter 1 describes "postfacilitation stretch" to release fibrosis in a muscle, and Lewitt (1999) Chapter 1 introduces Post-Isometric Relaxation as a way to normalise hypertonic muscles. Ballantyne et al (2003) do not refer to any of these sources,and do not state what the therapeutic objective was for the exercise; whether the contraction and subsequent stretch was to relax hypertonic muscles or to break down fibrosis. As a result, it is difficult to relate the technique they tested to any established MET. If it was to relax hypertonic muscles, then a more gentle contraction and a longer rest period before the stretch would resemble Lewit's Post-Isometric Relaxation method, as referenced by Chaitow (2006) page 82. If to release fibrotic tissue, a more intense contraction from a less stretched position then an immediate lengthy stretch would be indicated, according to Janda, as referenced by Chaitow (2006) page 83. How the protocol varies from established METThere an ongoing debate among therapists about the optimum protocol for muscle energy techniques, based on what therapists have found most effective in their practice. This has been supplemented by some research. However, Ballantyne et al do not discuss the reasons for their choice of protocol, but present it as the undisputed technique. As a result, it is difficult to check what pitfalls they aimed to avoid. In the research, the knees were extended until "discomfort" was felt then experimental subjects were asked to contract isometrically 70% of maximum effort (page 61). First, discomfort was not defined, and potentially could be interpreted by subjects either as "the first sign of resistance" (Chaitow 2006 page 79) or the point where the muscle spasms in protection. When muscles are extended until discomfort is felt, there can be what Norris (2004, page 30) calls a "resistance reflex" spasm created to protect the joint from damage. There is a risk of cramping in the antagonist or trauma to the agonist. While this exercise may be acceptable to healthy experimental subjects, for vulnerable people with acute or chronic conditions this exertion could be dangerous, risking further injury. The contraction was held for only 5 seconds. Chaitow (2006) recommends 7-10 seconds, and on page 84 notes Greenman (1989) warning an inadequately sustained contraction is a key error which can invalidate the procedure. Since Ballantyne et al quote Greenman's Principles of Manual Medicine in the paper, it is surprising they have not noted his advice. The rest period after each isometric contraction in the research was a mere 3 seconds. Chaitow (2006) on pages 97 and 99 recommends a minimum of 5 seconds before considering any lengthening of muscles, and furthermore, advice to relax and directing breath or eye movements to assist. On page 84 he refers to Greenman (1989) again, saying insufficient relaxation post-contraction is another key error. Although Moore & Kukulka (1991) noted the time for muscle inhibition after isometric contraction was very short, they speculated that the speed of relaxation may affect this time, referencing an earlier study where the post-isometric period plateaued up to 30 seconds post-contraction results (page 327). Ballantyne et al did not give information about training of the subjects in relaxation, or any helpful advice that might have been given by the testers (eg. Breathing or eye movements). No indication was given on what information the subjects were given, and how they should be expected to perform. This lack of training in post-isometric relaxation may have affected some key results. The experiment tested only once for range of motion after test using the same torque as was used pre-test (ROMpost1). The authors claimed (page 61) that they did not want to distort the ROMpost2 results by doing a repeated ROMpost1 test, as they understand static stretching can produce temporary visio-electric changes to tissue. It would have been far more effective if they had separated these 2 tests out completely - testing separate groups of subjects, after sufficient training in post-isometric relaxations. By confining the ROMpost1 test to the initial post-isometric relaxation, they were working with subjects untrained in relaxing after contraction. As the subjects were given only 3 seconds to relax before test, the testers could easily have been measuring a residual contraction in the muscles. The results for the control group showed a significant decrease in passive knee extension in ROMpost1 (page 62), which would suggest resistance reflex spasm after an initial ROMpre test, which may have taken the extension too far into "discomfort". The authors acknowledge measurement error may have played a role in this, however. Table 2 in the paper, titled Repeated measures ANOVA summary of differences in all groups, although it shows significant variance between Control and Experiment groups in Torque applied, is not referenced in the text and worse, the acronym ANOVA and columns titled "F" and "p" are not defined. The reader is left with no information to help them draw their own conclusions. Standardisation of the procedure: control of variablesAnother safety issue in the protocol is the securing of subjects' bodies to control testing. The subjects' other thighs were secured to the couch to minimise rotation of the pelvis, and the tested thigh looks in the illustration to be secured to a vertical post. However, no mention is made of securing the trunk to ensure no movement of the pelvis. The subjects' knee was extended to the first report of hamstring discomfort. There was no mention of how the elevated foot was managed (plantaflexion, rotation) to ensure a possible tight gastrocnemius is excluded from the study. The authors themselves acknowledge that a design flaw may have caused measurement error, noting outlier results. Other limitations on the value of the researchThe sample subjects were mostly young people (mean age 23) with a small majority being women. People with pathology were screened out. The authors acknowledged the limited sample and suggested testing people with a history of hamstring injury (page 62). As the research authors reference them, they seem to have taken their cue for the experiment from work done by Magnusson, Simonsen et al (1996), from the Team Danmark Test Center, the elite sports institution in Copenhagen. With more technology at their disposal, they produced detailed studies into PNF stretching compared with static stretches, and noted a greater degree of stretch tolerance before pain felt, particularly with contract-relax stretching, allowing a greater Range of Motion when torque increased. Although they had fewer subjects (10 male recreational athletes) the controls on the experiment were explicit: the contract-relax phase was safer at 10 degrees less than maximum stretch, and care was taken to avoid a painful response (page 374). Their conclusions seem to have been similar to Ballantyne et al (2003), but their research predates them by 7 years. AnalysisThe 2 objectives of the study were to "investigate the effectiveness of muscle energy technique in increasing passive knee extension and to explore the mechanism behind any observed change" (page 59). Ignoring the fact the experiment did not involve recognised Muscle Energy Techniques, let us first identify whether passive knee extension was affected. Certainly the experimental group outperformed the control group, which clearly shows there was some change in the tissue or neurological control, which will improve subjective experience. This benefit should not be underestimated, if it reduces discomfort and encourages movement. Whether the protocol is the most effective mechanism to do this has already been questioned, however. The other objective was to explore the mechanism behind any observed change. The experiment was focussing on whether change would be visco-electric change in tissue, meaning a de-facto change in the myofascial structures, or a neurological change in the perception of stretching. The report concluded that it was merely a neurological change, describing it as an "increased tolerance" to stretch, because greater torque was required to extend the knee beyond previous readings. However, there is a shortage of data to support this assertion, as a result of a weakness in the experiment. The experiment was correct in identifying that increased torque was needed to further extend the joint to the new point of "discomfort", and so there is an increase in tolerance. However, the experiment deliberately avoided repeating ROMpost1 recording - identifying the new range of motion with identical torque. The reason for avoiding it was they acknowledge passive stretching alone can change visco-electric properties in muscle. As the range of motion did not change after one application, they assumed that it has no effect, which is not necessarily true. For instance, waiting longer before repeating contractions and extending the knee might have yielded very different results. Perhaps conducting another experiment with one group repeatedly performing ROMpost1 procedure would have been significant. The report's assertions - did they meet their objectives?In their discussion, Ballantyne et al acknowledge a significant increase in hamstring extensibility in experiment subjects over controls. They assume after only one initial test that this increase did not happen with the same torque applied (ROMpost1). However, this was an initial test with untrained subjects, as already mentioned, where the control group measured a decrease in passive knee extension, suggesting cramping through over-enthusiastic stretching and so this assertion is on disputable empirical evidence. They conducted ROMpost2 3 times, and noted the increase in extensibility, but with extra torque tolerated. By this time the subjects would have understood the process, and may have been more actively involved. Missed opportunitiesThe paper does not explore whether the increased tolerance to stretch may have a therapeutic effect, or is contra-indicated, exposing the patient to an lesser awareness of the risk of injury in treatment. Furthermore, the extent of stretching during the experiment could have been counterproductive to the experiment. The researchers assumed that this increase in extensibility was based on increased tolerance to stretch - accepting a greater stretch before reporting "discomfort". They did not speculate on the cause of the tolerance, however. In this experiment, by the 3rd stretch, the subjects may have experienced considerable discomfort already, and may have endorphin or other chemical insulation to pain, not necessarily that the nerve response is inhibited by contract-relax. Norris' (2004) resistance reflex spasm may account for the necessary extra torque required to extend the joint further in subsequent ROMpost2 stretches. ConclusionsWhile Ballantyne et al have illustrated that increased tolerance to stretch may be a result of contract-relax techniques, which is an interesting conclusion, their assertion that visco-electric changes play no part is not adequately proven. No other possible factors to explain the results were explored: whether there is a change in the joint capsule, whether the experiment could have been performed differently. Unfortunately, this paper does not seem to seek to stimulate further research, but tries to answer the question with a closed answer. 2,198 Words
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