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International Journal of Osteopathic Medicine 12 (2009) 56–62

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International Journal of Osteopathic Medicine

journal homepage: www.elsevier .com/locate/ i jos

Research report

The effects of high-velocity low-amplitude thrust manipulation andmobilisation techniques on pressure pain threshold in the lumbar spine

Oliver Thomson a,b,c,*, Lesley Haig b, Hazel Mansfield c

a Stockholm College of Osteopathic Medicine, Stockholm, Swedenb School of Human Sciences, St Mary’s University College, Twickenham, UKc British College of Osteopathic Medicine, London, UK

a r t i c l e i n f o

Article history:Received 8 February 2008Received in revised form30 June 2008Accepted 18 July 2008

Keywords:OsteopathyAlgometryPainHypoalgesia

* Corresponding author. Stockholm College of Obergsgatan 49 (1 tr), 112 33 Stockholm, Sweden. Tel.:

E-mail address: oliver.thomson@hotmail.com (O. T

1746-0689/$ – see front matter � 2008 Elsevier Ltd.doi:10.1016/j.ijosm.2008.07.003

a b s t r a c t

Objective: To compare changes in pressure pain threshold (PPT) following spinal high-velocity low-amplitude thrust manipulation (HVLAT) and spinal mobilisation.

Design: Fifty asymptomatic subjects (mean age 27 (6) years; 29 males and 21 females) volunteered toparticipate in a randomised controlled, singled blinded design study. Subjects were screened for suitabilityand were randomly allocated into one of three intervention groups where they received either a unilateralspinal HVLAT or a spinal mobilisation of the lumbar spine, or a sham ‘laser’ procedure (control). PPTmeasurements were made immediately pre- and post-intervention, using a hand-held algometer whichwas positioned directly over the lumbar spinous process. A two-way ANOVA with repeated measures wasconducted to determine PPT changes between the groups. Statistical significance was set at the 0.05 level.

Results: There were no significant differences in PPT across time for each of the groups (P¼ 0.584). Themobilisation group displayed a small increase, though not a significant change in the mean pressure painthreshold (0.434(0.55) kg/cm2), although effect size was considered to be large (ES¼ 0.78). The HVLATgroup demonstrated a decrease in the mean PPT (�0.173(0.48)) (ES¼ 0.36, small), and a smaller decreasewas noted for the control group (0.105(0.425) kg/cm2) (ES¼ 0.25, small).

Conclusion: Neither spinal HVLAT nor mobilisation had a significant effect on PPT of the lumbar spine inasymptomatic subjects. Only spinal mobilisation appeared to have a greater mean increase in PPT andeffect size than the control group. Further investigation into the hypoalgesic effects of these techniqueson symptomatic subjects is suggested.

� 2008 Elsevier Ltd. All rights reserved.

16–18

1. Introduction

Spinal manipulative therapy (SMT) such as mobilisation andmanipulation techniques are commonly used by osteopaths, chiro-practors and physiotherapists for the treatment of low back pain anddysfunction. Spinal manipulation has been studied frequently inrandomised clinical trials1–4 with mobilisation receiving relativelyless attention. Both techniques have been subject to structuredreviews and meta-analyses which suggest that their use leads toclinically significant improvements in pain and function.5–14

Mobilisation involves oscillatory repetitive movements againsta restrictive barrier, and can be applied to a single articulation ormultiple spinal segments.15 Mobilisation techniques are performedat relatively low velocities, where the force and amplitude can be

steopathic Medicine, Krono-þ46 (0)738 529 119.homson).

All rights reserved.

controlled. Manipulation, as opposed to mobilisation, involvesa high-velocity low-amplitude thrust (HVLAT) directed to a syno-vial joint within a very short amplitude.19 There is commonly anassociated ‘pop’ or ‘cracking’ noise which has been termed ‘cavi-tation’ and is thought to occur as a result of the formation andcollapse of gas bubbles within the joint.17–20

It has been proposed that SMT has a number of therapeuticeffects, including the stretching of thickened peri articular softtissue, improving the range of motion, reducing oedema arounda joint and reducing pain.15,17,21,22 A large body of research hasinvestigated the effect of HVLAT on the modulation and reductionin pain levels.15,23–25 The mechanisms by which these effects areachieved are not yet fully understood, with a large number ofpossible theories suggested.19,26–33

1.1. Spinal HVLAT manipulation

A large proportion of the studies investigating the neurophysi-ological aspect of spinal HVLAT demonstrates a hypoalgesic effect

O. Thomson et al. / International Journal of Osteopathic Medicine 12 (2009) 56–62 57

that is significantly different from placebo, with a large number ofstudies initiating pain via the application of pressure on spinaltissues, termed pressure pain threshold (PPT).15,21,24,34,36–39

Terrett and Vernon34 carried out a study looking at changes inthe cutaneous receptive field following an HVLAT of the thoracicspine of 53 asymptomatic subjects. The results showed a signifi-cantly higher threshold to cutaneous pain over the paraspinaltissue of the manipulation group compared to the control group. Asthe control group received the same degree of manual contact andjoint motion as the HVLAT group, but did not receive a manipula-tion resulting in a cavitation, it is possible that the critical aspectwhich provided a hypoalgesic effect was the rapid thrust whichoccurred in an HVLAT.

Similar results have been seen following manipulation of thecervical spine.39–42 In a small study investigating subjects withneck pain, PPT values were shown to increase by an average of 40–56% for up to 5 min following the manipulation. There was nosignificant change in PPT in any of the control group subjects.However, due to the small sample size (n¼ 9), the results of thisstudy must be treated with caution.

More recently, Fryer et al15 reported that both manipulation andmobilisation had a significant effect of increasing the threshold topain when compared to a control group. It appeared that mobi-lisation was more effective for reducing PPT, producing a greaterimmediate improvement. These results were in contrast to those ofCassidy et al35 who demonstrated an immediate reduction inalmost 85% of the subjects following manipulation, which wasgreater than that reported by the mobilisation group, suggestingthat both techniques may have an immediate hypoalgesic effect.These results are in accordance with those observed by Vernonet al.21 Other studies have failed to show a significant decrease inpain following spinal HVLAT.36,37,43

A large body of evidence has suggested that hypoalgesiaobserved following SMT is a result of the activation of endogenousdescending pathways in the brain inhibitory systems, mediatedthrough the midbrain dorsal periaqueductal grey region(dPAG).23,24,31,41,44 It has been suggested that stimulation of dPAGproduces profound selective analgesia.23,24,31,41,44,45 It is known thatexcitation of the sympathetic nervous system results from stimu-lation of the dPAG46 and as such has received a considerable amountof attention in the literature. It is possible that these mechanismsplay a part in the short and long term relief in symptomatic patientsbut may not be relevant to hypoalgesia following HVLAT in pain freepatients.26,37 Sterling et al41 investigated the neurophysiologicalmechanisms of spinal mobilisation in subjects with neck pain bylooking at the associated sympathetico-excitatory effects. Followingmobilisation of the cervical spine, a hypoalgesic effect was demon-strated by way of a reduction in PPT and a mean decrease in VASscore. A sympathetic-excitatory effect was demonstrated by way ofa reduction in skin temperature and increase in skin conductance.

There have been other suggestions for the hypoalgesia seenfollowing spinal HVLAT. One such theory proposes that thereduction in pain is due to the activation of the endogenous anti-nociceptive system subserved by plasma b-endorphins.42,47,48

Vernon et al42 investigated this theory by measuring plasma b-endorphin levels in 21 subjects following a cervical spine HVLAT.Only the HVLAT group displayed a small though significant increasein b-endorphin levels following the intervention. Subsequentstudies into the b-endorphin system failed to show any significanteffect.47,48 However, Vernon29 identified methodological flaws usedby the investigators including a low sensitivity of assay levels usedto detect b-endorphin levels and also the region of the spinereceiving the manipulative procedure.

It is speculated that the gate control theory, as proposed byMelzack and Wall,27 may also play a role in hypoalgesia following

HVLAT. It is believed that large diameter myelinated neurons frommechanoreceptors modulate and inhibit the smaller diameternociceptive input at the level of the spinal cord. Both joint HVLATand mobilisation procedures would have the effect of stimulatingjoint mechanoreceptors through movement of the peri articulartissues, and thus inhibiting pain.26

1.2. Spinal mobilisation

Whilst spinal manipulation has undergone intense scrutiny,mobilisation has received relatively little investigation. A largeproportion of studies looking at the effects of lumbar mobilisationhas incorporated other treatments. For example, Farrell and Two-mey49 found that a combination of manipulation and mobilisationproduced a more rapid recovery of low back pain patients whencompared to a ‘control’ group receiving microwave diathermy,abdominal exercises and ergonomic education. This is in agreementwith Koes et al50,51 who, over two studies, compared four differentinterventions; combined manipulation and mobilisation, physio-therapy and treatments by the patients medical physician (con-sisting of medication and advice), and a placebo group. There wasthe greatest improvement in both the manipulation/mobilisationgroup and physiotherapy group, compared to the medical physicianand placebo groups.

To date, only a handful of studies have examined the effects ofspinal manipulation and mobilisation separately.25,45,52–54 Hadleret al53 directly compared the effect of manipulation and mobi-lisation on patients with acute low back pain. The group whoreceived manipulation had a greater improvement than the groupwho received mobilisation without a ‘rotatory thrust’. However,Goodsell et al25 found no measurable improvement in themechanical behaviour of the lumbar spine following anterior-posterior mobilisation in symptomatic subjects, but an improve-ment in pain free active movements of the spine was seen. Simi-larly, Petty54 observed no difference in flexion and extension rangesfollowing posterior-anterior mobilisations to the lumbar spine.However, numerous studies do show an improvement in spinalmechanics following mobilisation techniques.55–57

A number of authors have examined the influence of spinalmobilisation on the function of the sympathetic nervous system,with the aim to investigate the possible role the descending path-ways, projecting from the PAG, have in hypoalgesia.24,45,58–69 Apreliminary study by Peterson et al45 looked at the effect of a gradeIII posterioanterior mobilisation to the C5/6 joint of the cervicalspine in non-symptomatic subjects. The outcome measures of skintemperature and conductance of the finger tips were recorded asa measure of sudomotor and vasomotor activity. Compared to theplacebo group, skin conductance rose by 60%, whilst skin temper-ature decreased significantly. The authors concluded that mobi-lisations to the cervical spine have an immediate excitatory effecton the sympathetic nervous system, and a potential role in hypo-algesia. Similar results have been observed during mobilisation ofthe cervical spine in subjects with lateral epicondylitis.24

1.3. Pressure algometry

An aim of SMT is to attenuate the nociceptive component ofspinal pain, and there are a number of methods, with proven reli-ability, of assessing intervention-induced changes in nociceptivepain. Methods include verbal or numerical rating scales and visualanalogue scales61 and pain questionnaires such as the McGill PainQuestionnaire.62 The measurement of PPT via pressure algometry isanother method used to quantify a patient’s perception of a painfulexperience63 and has been shown to be a very reliable and rela-tively inexpensive method of measuring soft tissue tenderness64–72

O. Thomson et al. / International Journal of Osteopathic Medicine 12 (2009) 56–6258

and it is frequently used to measure the effect of SMT on soft andbony tissue.12,15,21,24,36–39,41,44 PPT can be defined as the leaststimulus intensity at which a subject perceives pain upon theapplication of pressure or force.63

A large proportion of investigations have established that bonedisplays a lower average PPT compared to muscle68,70,72; however,some authors dispute this and have reported no difference betweenPPT values over bone or muscle.71 A number of researchers haveshown regional differences of spinal PPT, and that threshold valuesincrease in the caudal direction64,70,72 and may be due to a higherdensity of nociceptors and mechanoreceptors in the cervical thanlumbar spine.64 There also appears to be gender differences in PPT,with females exhibiting a significantly lower PPT in the first dorsalinterosseous muscle than males.73

A number of studies have confirmed the reliability of pressurealgometry15,64,67,69 finding good intraobserver reliability for thelocation of unmarked myofascial trigger points. However, a numberof methodological issues have been identified with the use ofpressure algometry in previously published research.64,71,74–76

Numerous researchers have attempted to explain the hypo-algesic effects of SMT15,21,24,34–37,41,77 though to date, none havedirectly compared the hypoalgesic effects of manipulation andmobilisation on the lumbar spine. The aim of this study is toinvestigate and compare the effect that manipulation and mobi-lisation has on PPT in the lumbar spine in asymptomatic subjects.

2. Methods

2.1. Subjects

Fifty male (n¼ 29) and female (n¼ 21) subjects (mean age 27 (6)years) were recruited and were randomly assigned into eithera mobilisation group (n¼ 18, 12 males, five females), an HVLATgroup (n¼ 19, 10 males, 10 females) or a control group (n¼ 13,seven males, six females). All participants were recruited from thestudent and teaching population at the British College of Osteo-pathic Medicine (BCOM). Subjects were screened via a question-naire for any contraindication to SMT.78 Participants were excludedif they had received spinal manipulation or mobilisation techniqueswithin the last three days, or had any contraindications to spinalmanipulation. Both the BCOM and St Mary’s University Collegeethics committees granted ethical approval for the study.

2.2. Measurement of pressure pain thresholds

PPT was measured by using a hand-held manual pressurealgometer (pain test model FPK, Wagner Instruments, Greenwich,CT) (Fig. 1). This particular algometer model has been used to

Fig. 1. The algometer.

measure soft tissue pain associated with trigger points67–69 and hasmore recently, during a randomised control trial, been used tomeasure pressure pain thresholds at the sacro-iliac joint.79 A pilotstudy was conducted prior to the main study to assess the repro-ducibility of the examiner using the algometer. Three subjects, whowere not involved in the main study, received three PPTmeasurements before and after a 1 min interval. The intraclasscorrelation coefficient (ICC) was 0.78, indicating good (ICC> 0.75)reproducibility of PPT measurements.

The algometer was calibrated by the manufacturer, and a 1 cm2

rubber tip was used as this has been found to stabilise the algo-meter on a spinous process increasing reliability.15 In the presentstudy, the operator of the algometer undertook over 5 h of practicein the device before data collection began. It has been suggestedthat training in the device improves the reliability of the operator,in particular the rate of pressure application and cessation ofpressure once a verbal demand is given by the subject.76

The procedure used to measure PPTs was similar to that used byKeating et al72 and Fryer et al.15 The subjects received three ‘prac-tice’ measurements on the dorsal aspect of their hand beforetesting began. The subject lay prone on an adjustable plinth, andthe algometer was orientated perpendicular to the spinous processof a marked lumbar vertebra (Fig. 2). Subjects were asked to say‘now’ at the exact moment when the sensation of pressure changedto one of pain. The researcher then immediately ceased the pres-sure, and the maximal pressure applied was recorded as the PPTvalue.

Pressure was applied to the algometer at a rate of 1 kg/s, usingprotocols developed by Fischer.69 Three measurements were takenper subject, with a 20 s break between each one, and the averagecalculated as the PPT for that participant. It has been demonstratedin previous studies that repeated application of the algometer doesnot alter the sensitivity of the tissue being measured.65

2.3. Procedure

Subjects were asked to undress to expose their spines and layprone on the plinth. There were two researchers involved in testing.To identify the most-tender lumbar spinous process, researcher 1used a springing technique in a posterioanterior direction, applyingpressure twice to each lumbar spinous process, and the mosttender was marked with a skin pencil. Researcher 1 then proceededto take three PPT measurements of the marked segment, witha 20 s break between each measurement. Researcher 1 then exited

Fig. 2. PPT measurement.

Fig. 4. Experimental mobilisation technique.

O. Thomson et al. / International Journal of Osteopathic Medicine 12 (2009) 56–62 59

the room and researcher 2 entered the room to perform theselected intervention. Immediately after the intervention,researcher 1 re-entered the room to measure the post-interventionPPT. Researcher 1 was blinded to the intervention received andresearcher 2 was blinded to the pre- and post-intervention PPTvalues.

2.4. Manipulation intervention

The HVLAT group received a single HVLA thrust to the identifiedlumbar segment (Fig. 3). The thrust delivered was a right sidedrotational thrust technique. The subject was instructed to lie on theright side and researcher 2 (a registered osteopath) addedcomponents of rotation and side-bending, using the upper torsoand pelvis as leverage. The thrust was delivered to the inferior jointof the marked segment. For example, if L3 was identified andmarked as the most-tender segment, then the joint between L3 andL4 received the HVLA thrust. These techniques are described innumerous osteopathic texts.78,80

2.5. Mobilisation intervention

Subjects in the mobilisation group received a mobilisation intoright rotation for 30 s (Fig. 4). This was achieved by the subjectslying prone on the plinth, and researcher 2 standing on their leftside. The researcher firmly contacted the transverse process(through the paravertebral soft tissue) of the marked segment, andinitiated a rotational movement by pulling on the anterior surfaceof the pelvis with the other hand. These techniques are described inspinal manipulative texts.81,82

2.6. Sham laser treatment (control)

A sham group was employed instead of a non-interventiongroup as a control group, in order to ensure a similar expectationbias in all groups. The sham intervention was designed to controlfor any placebo effect. The control group received 30 s of ‘laseracupuncture’, with a laser pointer. Prior to receiving the interven-tion the subjects were shown the laser being applied to the dorsumof their hand. The subjects lay prone on the plinth, with the laserpointer directed at the marked lumbar segment. Subjects wereinformed that this technique was a commonly employed modalitypracticed by acupuncturists. The laser was turned off throughoutthe treatment.

Fig. 3. Experimental HVLAT technique.

2.7. Statistical analysis

All data collected were analysed using the statistical packageSPSS version 11. To establish the reliability of the PPT measurementprocedure, the intraclass correlation coefficient (ICC, based ona one-way ANOVA) was calculated for the PPT readings obtainedfrom the pilot study. To determine if differences existed betweenthe changes produced by the three interventions, a two-wayANOVA with repeated measures was conducted, and the pre-posteffect sizes (Cohen’s d) calculated. Statistical significance was set atthe 0.05 level.

3. Results

Mean(SD) PPT values are shown in Fig. 5. The ANOVA revealedthere were no significant differences across time for each of thegroups (P¼ 0.584). The mobilisation group displayed a smallincrease, though not a significant change in the mean pressure painthreshold (0.434(0.55) kg/cm2), although effect size was consideredto be large (d¼ 0.78). The HVLAT group showed a decrease in themean PPT (�0.173(0.48)) (d¼ 0.36, small), and a smaller decreasewas noted for the control group (0.105(0.425) kg/cm2) (d¼ 0.25,small).

The ANOVA further revealed that there was a non-significantinteraction between time and the treatment groups. This can be

0.000

0.500

1.000

1.500

2.000

2.500

3.000

Pre Mob Post Mob Pre Man Post Man Pre CTRL Post CTRL

Group

PP

T (

Kg/

cm2)

MeanSD

Fig. 5. Mean PPT changes with SD.

0

0.5

1

1.5

2

2.5

3

Pre Post

Time

Kg/cm2

MobManControl

Fig. 6. Pre- and post-PPT measurements across the three groups.

Table 2ANOVA: mean ages between groups

Sum of squares df Mean square F P

Between groups 227.87 2 113.93 2.15 0.13Within groups 2487.81 47 52.93Total 2715.68 49

O. Thomson et al. / International Journal of Osteopathic Medicine 12 (2009) 56–6260

seen in Fig. 6, where the mobilisation group displayed a rise in PPTover time, and both the manipulation and control groups hada marginal decline in PPT values over time.

Mean group ages were calculated (Table 1) and an ANOVA wasperformed, which showed no significant difference between theages of the subjects either within or between groups (Table 2).

4. Discussion

Both HVLAT manipulation and mobilisation techniques are usedby a range of manual therapists to treat lower back pain and spinaldysfunction. This was the first study of its kind to directly comparethe effects of both techniques on lumbar spine PPT values. Thisstudy failed to demonstrate any significant difference in the PPT ofthe lumbar spine following either technique (P¼ 0.584). Themobilisation group displayed a slight increase in the mean PPT(0.434(0.55) kg/cm2), and the HVLAT group showed a minordecrease in PPT (�0.173(0.48)), with the respective effect sizesbeing large (d¼ 0.78) and small (d¼ 0.36). A number of studieshave shown that such techniques have a positive effect on painreduction.15,21,24,34–38,83 The results obtained in this study are incontrast with those of Fryer et al15 who found significant increasesin PPT in subjects receiving either an HVLAT or mobilisation of thethoracic spine, with mobilisation appearing more effective.However, the results from the present study do suggest thatmobilisation may have a stronger effect on PPT compared to HVLAT.

It is thought that PPT values increase with age.84 The mean agesof each group were calculated (Table 1), and an ANOVA was per-formed, which showed that there was no significant difference

Table 1Mean group ages with SD

n Mean Std. deviation Effect size (d)

Control 13 24.38 4.46 0.25Mobilisation 18 26.00 6.95 0.78Manipulation 19 29.53 8.91 0.36

(P¼ 0.13) in subject ages between and within groups (Table 2),suggesting that subject age was not a significant factor in this study.Uneven group numbers and male to female ratios within eachintervention group may also have had an impact on the resultsobtained, particularly with regard to gender, as females tend toexhibit a lower PPT than males.73

A number of studies have found that PPT values increase ina caudal direction64,69,70,72,85 and it has been suggested that this isdue to a lower mechanoreceptor and nociceptor density in thelumbar spine.64 This could offer a theory behind the non-significantresults obtained in this study, and why a large number of studieshave displayed increases in PPT following SMT applied to thecervical spine.21,35,37–39,41 When considering the gate controltheory,27 which relies on large, myelinated neurons from mecha-noreceptors to modulate and inhibit nociceptive input from smalldiameter neurons, a lack of mechanoreceptor activity followingSMT to the lumbar spine would be unable to ‘close’ the pain gateand create a hypoalgesic effect.

One possible theory of hypoalgesia following SMT involves therelease of endorphins which are thought to participate in anti-nociception, with a number of studies measuring plasma b-endorphin levels following SMT.42,47,48 It has been suggested thatplasma b-endorphin is derived from pituitary gland secretion, anddepends on central hypothalamic activation, which would notoccur following SMT performed on the lumbar spine29 and mayaccount for the non-significant change in PPT seen in this study.

The absence of clinically or statistically significant results maybe attributed to a number of factors and limitations of this study.The choice of the mobilisation technique used may have hada bearing on the results obtained. A rotational mobilisation tech-nique was employed in this study, which was preferred for twomain reasons; it involved the subject remaining in the proneposition pre- and post-testing, and secondly it was performed ina different position from the sidelying manipulation techniqueused, which was considered to be important to ensure that bothtechniques differed sufficiently from each other. However, thelimitation with this technique performed on this area of the spine isthe very small amount of rotation available in the lumbar spine.86,87

It may be theorized that if a flexion mobilisation had been used,which allows almost five times greater motion than rotation,86 theresults may have been different, due to a greater mechanical andneurological effect.

Three of the subjects in the HVLAT group did not produce anaudible cavitation when the manipulation was applied, which mayhave contributed to the relative decrease in PPT in the HVLATgroup. Conversely studies have suggested that there is little to norelationship between the manipulative ‘pop’ and improvedoutcome.88,89 Furthermore it has been demonstrated that whenaudible cavitation does arise during an HVLAT we cannot be certainfrom which joint the cavitation occurred.90

All of the subjects were osteopathic students, and although itwas explained that laser acupuncture was a genuine intervention, itis believed by the researchers that the control subjects may havebeen aware of the sham procedure; however no follow-up studywas conducted to ascertain if this was the case. There was a smallmean decrease in PPT in the control group (0.105(0.425) kg/cm2),with a small effect size (d¼ 0.25) suggesting that there was little to

O. Thomson et al. / International Journal of Osteopathic Medicine 12 (2009) 56–62 61

no placebo effect. Time constraints of the study meant that onlya relatively small sample size of 50 subjects could be recruited,resulting in uneven group numbers. A small sample size may not berepresentative of the general population, and may reduce thepower of the study, increasing the likelihood of non-significantresults.

The measurement of pain is difficult and there are numerousmethods used to quantify a subject’s painful experience.61,62,91 Anumber of studies have reported good reliability of pressure algo-metry15,64,65,69; however there are reported methodological flawswith pressure algometry64,71,74,75 and this study is no different. Thepresent study used a mechanical algometer, which does not possessthe facility to control the rate of pressure application. Electronicalgometers are considered to be more accurate and produce betterreliability due to the non-reliance on investigator reaction time.76

This study looked at two techniques in isolation; however in clin-ical practice these techniques are applied differently, usually morethan once within a treatment session, in conjunction with othertechniques and on symptomatic patients. As such, further researchshould incorporate the application of SMT techniques on symp-tomatic patients in a way in which they would be used in a clinicalsetting. Additionally, only the immediate hypoalgesic effects of SMTwere investigated during the present study; further research couldhighlight PPT changes which may only be observable minutes oreven hours after treatment. It has been established that minoradverse events, such as a worsening of the present symptoms or theonset of new symptoms, are common during the 24–48 h followingspinal manipulation.92 This occurrence is often termed a ‘treatmentreaction’ or ‘rebound reaction’, and has been identified in osteo-pathic texts as a relatively common and predictable response.93 Forthis reason, it may be of no surprise that the HVLAT group displayeda slight reduction in PPT following the intervention. As such,further follow-up measurements taken beyond this period mayhave revealed an increase in PPT.

5. Conclusion

This was the first study to compare the effects of spinal mobi-lisation and HVLAT manipulation on PPT over the lumbar spine, inasymptomatic subjects. Neither technique significantly producedchanges in PPT, with the mobilisation group displaying a greatermean increase in PPT than both the HVLAT and control groups,which may indicate that spinal mobilisation has a greater imme-diate effect on PPT than spinal HVLAT. Future research wouldinvolve comparing the pain relieving properties of differentcombinations of SMT techniques on symptomatic subjects. It isrecommended that PPT be measured and monitored over a longerperiod of time following the application of both these SMT tech-niques to account for rebound reactions resulting in hyperalgesia.

Acknowledgements

I would like to thank Dr Ian Drysdale for his valuable commentsand Dr Conor Gissane for his assistance in the study design andstatistical support.

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