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Cervical & thoracic manipulations: Acute effects upon pain pressure threshold and self-reported pain in experimentally induced shoulder pain
Manual Therapy xxx (2015) 1e6
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Original article
Cervical & thoracic manipulations: Acute effects upon pain pressure threshold and self-reported pain in experimentally induced shoulder pain Craig A. Wassinger a, *, Dustin Rich a, Nicholas Cameron a, Shelley Clark a, Scott Davenport a, Maranda Lingelbach a, Albert Smith a, G. David Baxter b, Joshua Davidson a a b
Department of Physical Therapy, East Tennessee State University, Johnson City, TN, USA School of Physiotherapy, University of Otago, Dunedin, New Zealand
a r t i c l e i n f o
a b s t r a c t
Article history: Received 9 April 2015 Received in revised form 8 July 2015 Accepted 18 August 2015
Background: Emerging evidence suggests that cervical and thoracic joint manipulations may be advocated in treating patients with shoulder pain. Objectives: To determine the acute effects of cervical, cervicothoracic, and thoracic joint manipulations on outcomes of self-reported pain and pain pressure threshold in experimentally induced shoulder pain. Design: Repeated measures. Methods: Twenty (20) healthy volunteers were tested on two sessions. Session 1 consisted on baseline assessment of pain pressure threshold testing over the infraspinatus bilaterally and self-reported shoulder pain using the shoulder pain and disability index (SPADI) pain scale. An isokinetic exercise protocol was used to induce delayed onset muscle soreness. In session 2 (24e48 h later), all variables were reassessed before and immediately after a combination of cervical, cervicothoracic and thoracic manipulations. Results: SPADI pain scale scores were significantly different between time points (p < 0.001): the exercise protocol significantly increased reported pain [mean increase 14.1, p < 0.001] while the manipulation significantly decreased reported pain (mean decrease 5.60, p < 0.001)) although pain remained higher than baseline levels. Pain pressure threshold differences were also found between time points (p ¼ 0.001): manipulation significantly increased pain threshold bilaterally (p < 0.001) similar to baseline levels. Conclusions: Cervical, cervicothoracic, and thoracic joint manipulations acutely increased pain pressure threshold and decreased self-reported shoulder pain in participants with experimentally induced shoulder pain. Physiotherapists may consider the combination of such techniques to achieve short-term hypoalgesic effects and facilitate the application of more active interventions. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Experimental shoulder pain Cervical and thoracic manipulation Manual therapy
1. Introduction Shoulder pain is among the most common pain location with point prevalence rates ranging from 7 to 26% in the general population (Luime et al., 2004). Given this, physical therapists have many interventions directed toward decreasing patients' complaints of shoulder pain including exercise, joint mobilization, and electrical and thermal modalities (Green et al., 2003).
* Corresponding author. Tel.: þ1 423 439 8295; fax: þ1 423 439 8077. E-mail address: [email protected] (C.A. Wassinger).
Manual therapy, specifically vertebral joint manipulation, is commonly utilized and advocated in treating a variety of musculoskeletal disorders (Flynn et al., 2002; Wainner et al., 2007; Iverson et al., 2008; Boyles et al., 2009; Mintken et al., 2010; Childs et al., 2011; Delitto et al., 2012). A recent systematic review has indicated that there is potential for benefit of shoulder conditions by treating the thoracic spine with manual therapy (Walser et al., 2009). The concept underlying this type of treatment has been described as regional interdependence, whereby impairments in one region can be linked, biomechanically and/or neurophysiologically, to impairments in neighboring anatomical regions (Wainner et al., 2007; Bialosky et al., 2009). Emerging evidence has
http://dx.doi.org/10.1016/j.math.2015.08.009 1356-689X/© 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Wassinger CA, et al., Cervical & thoracic manipulations: Acute effects upon pain pressure threshold and selfreported pain in experimentally induced shoulder pain, Manual Therapy (2015), http://dx.doi.org/10.1016/j.math.2015.08.009
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C.A. Wassinger et al. / Manual Therapy xxx (2015) 1e6
suggested utilizing spinal manual therapy to cervical and thoracic regions to treat patients with shoulder pain (Bergman et al., 2004; Boyles et al., 2009; Mintken et al., 2010; Muth et al., 2012). Reported benefits of spinal treatments for shoulder patients include increased pain free shoulder range of motion, decreased overall pain, improved self-reported function, and decreased provocative testing for shoulder injury (Mintken et al., 2010; Muth et al., 2012). One of the challenging aspects of treating shoulder pain is the range of pathoanatomical diagnoses that may be involved in pain origination (Dean et al., 2013). Unlike clinical practice, experimental pain models provide the opportunity for assessment of the efficacy of interventions on a reasonably uniform type of injury or painful condition (Staahl and Drewes, 2004). This study utilized an exercise induced delayed onset muscle soreness pain protocol. This method of simulating shoulder pain is appropriate given the pathophysiology and inflammatory changes created are similar to acute shoulder injury commonly found in younger individuals (Clarkson and Hubal, 2002; George et al., 2007). The aims of this paper were to determine the impact of cervical, cervicothoracic and thoracic manipulation on experimentally induced shoulder pain in a group of healthy young volunteers using both subjective selfreported pain measures and objective quantitative sensory testing (pain pressure threshold). 2. Methods 2.1. Participants A sample of convenience consisting of healthy volunteers participated in this study. Participants were between the ages of 23 and 27 years. This age group was specifically chosen to decrease the likelihood of age related degeneration of the shoulder muscles (Milgrom et al., 1995). Participants were considered healthy using the following criteria: denied any history seeking medical care for shoulder or neck injuries, and reported no current (past 6 months) shoulder or neck pain. Exclusion criteria consisted of prior shoulder surgery or fracture, and contraindication to cervical or thoracic manipulation as determined by medical screening from the principal investigator (CAW) (Cook, 2012). Participants were not seeking treatment for any other musculoskeletal disorder either. All testing was completed in a University research laboratory using procedures approved by the East Tennessee State University Institutional Review Board. All participants provided informed consent as per University guidelines. Equal numbers of males and females were recruited as differences have been noted in pain reporting between genders (Stohler et al., 2001). 2.2. Study design A repeated measures design was employed in this project with testing occurring in 2 sessions completed on separate days (Fig. 1). The first testing session consisted of screening for vertebrobasilar insufficiency (VBI), baseline outcome measures [self-reports shoulder pain (shoulder pain and disability index (SPADI) pain scale only); pain pressure threshold], maximal isometric shoulder strength in a modified neutral position, and completion of a standardized eccentric exercise protocol designed to induce shoulder pain via delayed onset muscle soreness (Chapman et al., 2006; Chen et al., 2009). Participants returned for day 2 of testing 24e48 h after the first session as peak soreness has been reported to occur between 24 and 72 h post exercise. They were asked not to exercise their upper body or utilize any treatments (ice, Non-steroidal anti-inflammatory drugs (NSAIDs), etc.) to reduce the shoulder pain. Day 2 testing consisted of repeated outcome measures, collected as noted (Cheung et al., 2003) above, VBI screening,
Fig. 1. Participant testing outline.
and the application of cervical and thoracic manipulations. The acute effects of the manipulations were then measured again using the outcomes described. Specific details on all procedures are described below. 2.3. Outcome measures The self-reported questionnaire used in our study was the SPADI pain scale, which comprises 5 questions referring to the severity of pain experienced in the shoulder. The entire SPADI includes a selfreported disability scale and a self-reported pain scale. The disability scale was not used in this investigation. The entire SPADI has been shown to demonstrate acceptable reliability, internal consistency, validity and responsiveness (Roy et al., 2009). Total score ranges from 0 to 50, with 0 as no pain and 50 as the highest pain score. If there was any presence of pain at baseline (a score other than 0) or if there was no change in SPADI score from baseline, meaning no presence of experimental pain, then the participant was excluded from further testing. Pain pressure threshold is the minimal amount of pressure required for the sense of pressure to change to pain (Nussbaum and Downes, 1998). A digital algometer (Wagner, Pain Test FP Algometer, Greenwich, CT) with a 1 cm2 blunt tip was used for testing. Pain pressure threshold was tested over the infraspinatus muscle belly with the participant in prone in the anatomical position. Testing occurred bilaterally as means to determine the systemic effects of the manipulations. The infraspinatus muscle belly was located by palpation inferior to the approximate midpoint of the scapular spine (Fig. 2). When the participant appreciated the vertical force as pain the algometer was removed and the peak force recorded. Standardized procedures for use of the pressure algometer were performed by the same investigator for all measures, with the average of three measurements used for analysis (Nussbaum and Downes, 1998). The time between pain pressure threshold measures was not standardized. Training on pain pressure threshold measurement procedures was performed prior to initiation of the study. 2.4. Experimental pain protocol Following collection of baseline outcome measurements, participants performed a concentric/eccentric exercise protocol on the
Please cite this article in press as: Wassinger CA, et al., Cervical & thoracic manipulations: Acute effects upon pain pressure threshold and selfreported pain in experimentally induced shoulder pain, Manual Therapy (2015), http://dx.doi.org/10.1016/j.math.2015.08.009
C.A. Wassinger et al. / Manual Therapy xxx (2015) 1e6
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screening for manual interventions targeting the cervical spine. The screening performed included sustained rotation of the cervical spine for 10 s, followed by 10 s in neutral. This was then performed to the contralateral side (Magarey et al., 2004; Arnold et al., 2004). Further, a premanipulative hold was sustained for 10 s in the treatment position with an additional 10 s assessment in neutral to determine if any delayed effects were present (Arnold et al., 2004). 2.6. Interventions
Fig. 2. Pain pressure testing participant position.
non-dominant (non-throwing) shoulder using an isokinetic dynamometer (HUMAC Norm Isokinetic Dynamometer, Computer Sports Medicine Institute, Stoughton, MA). This protocol was designed to induce delayed onset muscle soreness of the external rotators as the experimental shoulder pain condition (Chapman et al., 2006; Chen et al., 2009). The exercise protocol consisted of 3 sets of 30 repetitions of concentric external rotation at 60 / s followed by an eccentric return at 300 /s in a modified neutral position (Fig. 3). The dynamometer was set to move through a 50 arc of motion (25 internal and external rotation from neutral). External rotation isometric strength testing was performed prior to and immediately following the exercise protocol. Participants whose strength had not decreased by more than 50% from the baseline strength measurement were required to complete additional sets of 30 repetitions until the required 50% reduction in strength was achieved (George et al., 2007).
2.5. VBI screening VBI screening was performed twice as part of the study protocol. The initial test was to determine eligibility based on the inclusion/ exclusion criteria. The second administration was included in accordance with published guidelines on premanipulative
All participants received high velocity low amplitude (HVLA) thrust manipulation to their cervical spine, cervicothoracic region, and thoracic spine (Fig. 4). The targeted spinal levels for the cervical spine were C5, C6, and C7 utilizing a cervical lateral thrust technique with the force directed toward the contralateral eye ndez-de-las-Pen ~ as et al., 2007; Ruiz-Sa ez et al., 2007). HVLA (Ferna were performed at each segment until cavitation was noted by the participant or investigator for up to 2 attempts. If no cavitation was noted after 2 attempts, the investigator moved on to the more distal segment (Boyles et al., 2009). The same guidelines for treatment were applied to all interventions performed. Following cervical spine treatments the cervicothoracic region was treated using a distractive technique (Boyles et al., 2009; Mintken et al., 2010). Finally, a prone extension biased posterior to anterior technique was performed at the apex of the thoracic kyphosis, and to the proximal and distal 2 segments for a total of 5 targeted interventions in the thoracic spine. The segments for manipulation in the cervicothoracic and thoracic spine were included to be consistent with prior related investigations for shoulder disorders (Boyles et al., 2009; Mintken et al., 2010). Cervical levels C5eC7 were also chosen based on prior reports of non-thrust manual therapy for shoulder disorders (Mintken et al., 2010) and as the nerve root levels (C5eC6) for the suprascapular nerve (infraspinatus innervation). 2.7. Data analysis Repeated measures analyses of variance (ANOVA) were used to compare SPADI pain scores between baseline, pre-manipulative, and post-manipulative time points (SPSS Inc., Chicago, IL). Furthermore, a two-way ANOVA was used to evaluate change in pressure pain threshold with side (dominant, non-dominant) as the between-subjects factor and time (baseline, pre-manipulation and post-manipulation) as within subject factors. If the Mauchly sphericity test was statistically significant, degrees of freedom were corrected using the GreenhouseeGeisser method. Post hoc paired t-tests were used as appropriate. Significance was set at p 0.05. Effect sizes (ES) were also calculated using the effect size index [(pre-manipulative score post-manipulative score)/standard deviation pre-manipulative score]. Further, intraclass correlation coefficient (ICC3,1) and standard error of measurement (SEM) were calculated to assess reliability of pain pressure threshold data using the 3 trials from the baseline measurement. 3. Results
Fig. 3. Isokinetic setup.
Twenty-three participants completed day one of testing. Of these, twenty participants were able to complete day two of testing and, therefore, were included in data analysis (Table 1). Of the three participants excluded after testing day one, two subjects did not report any pain as of the SPADI after day one, and the third participant was excluded because of equipment malfunction. All participants were negative for VBI based on our screening. Baseline SPADI pain scores were 0 for all participants. SPADI pain scores were significantly different between time points
Please cite this article in press as: Wassinger CA, et al., Cervical & thoracic manipulations: Acute effects upon pain pressure threshold and selfreported pain in experimentally induced shoulder pain, Manual Therapy (2015), http://dx.doi.org/10.1016/j.math.2015.08.009
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C.A. Wassinger et al. / Manual Therapy xxx (2015) 1e6
Fig. 4. Cervical, cervicothoracic, and thoracic manipulations.
Table 1 Demographic data.
Males Females
Participants
Age (years)
Weight (kg)
Height (cm)
Right hand dominance
Baseline SPADI pain scale scores
10 10
24.8 ± 1.2 24.4 ± 1.8
84.1 ± 16.4 64.8 ± 11.6
179.3 ± 6.4 165.1 ± 6.6
8 9
0.0 ± 0.0 0.0 ± 0.0
Values are expressed as mean ± standard deviation.
(p < 0.001). Post hoc testing revealed the exercise protocol significantly increased reported pain [mean increase 14.1, p < 0.001]. The manipulation protocol significantly decreased reported pain (mean decrease 5.60, p < 0.001, ES ¼ 1.24); however pain remained higher than baseline levels (mean difference 8.50, p < 0.001). Reliability of pain pressure threshold testing was shown to be acceptable with ICC ¼ 0.985 (95% CI: 0.994e0.969) and a SEM ¼ 0.453 kg/cm2. No interaction (side time point) was found (F ¼ 0.208, p ¼ 0.761). However, the main effect of time point was significant (F ¼ 9.659, p ¼ 0.001), thus differences existed between baseline, pre-manipulation, and post-manipulation. Post hoc testing revealed pain pressure threshold values did not differ between baseline and pre-manipulative time points for dominant (p ¼ 0.556) and non-dominant (p ¼ 0.160) sides. Manipulation significantly increased pain pressure threshold bilaterally (dominant p < 0.001) and non-dominant (P < 0.001) (Table 2), yet these values were not significantly higher than baseline values (dominant p < 0.072) and non-dominant (P < 0.157). The increase in pain pressure threshold following manipulation represents an average increase in pain threshold by 25%. The effect size of the manipulation was near 0.40 bilaterally thus indicating a moderate change has occurred. 4. Discussion This study measured the effect of cervical, cervicothoracic and thoracic manipulation on 2 measures of pain, a self-reported measure of shoulder pain related to severity and function, and an objective measure of pain pressure threshold. Both measures
of pain were found to significantly improve immediately following manipulations with moderate to large effect sizes noted. These findings indicate spinal manipulation has an immediate local and systemic hypoalgesic effect on shoulder pain induced by delayed onset muscle soreness. The increase in pain threshold was approximately 25% bilaterally with moderate effects sizes near 0.4. Increases in pain pressure threshold greater than 15% have been reported to be clinically meaningful (Chesterton et al., 2007). Thus, both statistical and clinically significant changes in pain pressure threshold were noted immediately following the manipulations performed in this study. The increased pain pressure threshold findings are in accordance with conclusions from recent systematic reviews (Coronado et al., 2012; Voogt et al., 2014). A unique aspect of this study was the measurement of selfreported pain changes immediately following the manipulations, in addition to pain pressure threshold. The SPADI pain scale questions addressed pain severity and pain during functional activities. Cervical, cervicothoracic and thoracic manipulation was shown to be of significant benefit to participants' self-reported pain. The minimal clinically important difference of the entire SPADI (pain and disability scales) has been reported to be 8 points (Roy et al., 2009). Interpretations of the pain scale in isolation are difficult, yet the mean increase in pain scores from 0 to 14.1 indicate the exercise protocol was able to impart a clinically relevant painful condition. However, the acute effects of the manipulations decreased the mean self-reported pain by 5.6 points; therefore, the clinical significance of the reported pain decrease (i.e. in isolation) is more difficult to interpret. Given the high effect size, this
Table 2 Pain pressure threshold (PPT) outcomes. Mean (standard deviation)
Baseline PPT Pre-manipulation PPT Post-manipulation PPT
Dom
ND
5.73 (3.60) 5.46 (3.20) 6.69 (3.31)
5.67 (3.61) 5.02 (3.19) 6.41 (3.14)
Mean side-to-side difference
Mean time point difference (% change)
Effect size
0.06 0.44 0.28
Dom 0.27 (4.7) 1.23 (22.5)
Dom 0.07 0.38
ND 0.65 (11.5) 1.39 (27.7)
ND 0.18 0.44
Dom: Dominant, ND: Non-Dominant. All values in kilograms/cm2, % change ¼ time point difference/starting time point value 100%.
Please cite this article in press as: Wassinger CA, et al., Cervical & thoracic manipulations: Acute effects upon pain pressure threshold and selfreported pain in experimentally induced shoulder pain, Manual Therapy (2015), http://dx.doi.org/10.1016/j.math.2015.08.009
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indicates a strong relationship between the decreased shoulder pain and the manipulations. A similar positive effect on self-reported pain and function in patients seeking treatment for shoulder injury has been shown in prior studies over in the short term (2e3 days) (Boyles et al., 2009; Mintken et al., 2010). The results from the current study and prior investigations indicate there is a potential benefit of spinal manual therapy for patients with shoulder pain with acute and short term follow up (Boyles et al., 2009; Mintken et al., 2010; Muth et al., 2012); in contrast, longer term outcomes have been mixed (Winters et al., 1997; Bergman et al., 2004; Savolainen et al., 2004; Cook et al., 2014). Wide variability in shoulder conditions, treatment types, follow-up period, and outcome measures makes direct comparison of previous results difficult. Some prior studies have shown long term (11e52 weeks) improvement in shoulder pain when comparing spinal manual treatment to NSAID's, exercise, massage, and modalities (Bergman et al., 2004; Savolainen et al., 2004), while other studies (Winters et al., 1997; Cook et al., 2014) have shown equivocal or mixed results. The main limitation of most of the long-term studies is that the interventions used (manipulation only versus exercise, modalities and massage) did not represent standard clinical practice. In routine clinical practice, a multimodal approach including exercise, manual therapy, and additional thermal or electrical modalities are utilized to treat shoulder pain (Michener et al., 2004; Tate et al., 2010; Cook et al., 2014). In line with this, a recent trial by Cook et al. (2014) found no differences in reported outcomes between groups when spinal manual treatments (Grade III mobilizations) were added to usual care (exercises, modalities, etc.). The intervention combinations (manual therapy plus exercise) used in the trial by Cook et al. (2014) likely best represent standard physical therapy treatment for shoulder pain. Contrary to our study however, they used a lower grade spinal manual treatment (Grade III mobilizations versus manipulation) on shoulder impingement patients; thus direct comparisons are difficult. Although the mechanisms underlying the positive effect of the applied intervention were not addressed directly in this study, some discussion is warranted. It is possible that both segmentally mediated and central inhibitory mechanisms were responsible for the pain changes found in this study. Vertebral joint stimulation at the associated nerve roots of the shoulder muscles and scapula (C5T2) may affect the pain pressure threshold over infraspinatus bilaterally as well as reported pain at the shoulder. Segmental inhibition may have occurred due to stimulation of large diameter low-threshold mechanoreceptors (Katavich, 1998). Additionally, the spinal manipulations may have created a stimulus to activate the descending inhibitory pain systems such as autonomic and opioid systems (Vicenzino et al., 1998, 2001; Skyba et al., 2003). Any one or a combination of the above mentioned mechanisms may have played a role in the observed effects of bilaterally decreased pain pressure threshold and self-reported pain. There are some limitations to our study which should be noted. First, the participants in this study were healthy volunteers with experimentally induced mild muscle pain. The response of shoulder patients with a variety of conditions (specifically nonmusculotendinous injuries), and higher pain levels, may differ from the outcomes reported here. However, prior studies have shown positive effects for shoulder pain patients with manipulation (Boyles et al., 2009; Mintken et al., 2010; Tate et al., 2010; Muth et al., 2012). Secondly, no comparison group (sham intervention or control) was included for comparison. Prior investigations however, have shown no effect of sham or control on pain pressure ndez-de-las-Pen ~ as threshold variable on healthy participants (Ferna ~ as et al., 2008). Finally, it is et al., 2007; Fern andez-De-Las-Pen possible that the act of manipulation, including the noise, created
5
during the manipulations created a placebo effect (Bishop et al., 2011); this would be difficult to quantify and was beyond the scope of this study. 5. Conclusions This study demonstrated clinically significant acute pain reduction in participants with experimentally induced shoulder pain following spinal manipulation. The use of cervical, cervicothoracic and thoracic manipulation may be considered an appropriate intervention by physical therapists treating patients with painful shoulder conditions, where such treatments are otherwise not contraindicated. The acute decreases in pain following manipulation may allow more aggressive participation in a standard multimodal treatment approach including active exercise, selective stretching, and functional retraining earlier in the rehabilitation process. References Arnold C, Bourassa R, Langer T, Stoneham G. Doppler studies evaluating the effect of a physical therapy screening protocol on vertebral artery blood flow. Man Ther 2004;9:13e21. Bergman GJD, Winters JC, Groenier KH, Pool JJM, Jong BM, Postema K, et al. Manipulative therapy in addition to usual medical care for patients with shoulder dysfunction and pain. Ann Intern Med 2004;141:432. Bialosky JE, Bishop MD, Price DD, Robinson ME, George SZ. The mechanisms of manual therapy in the treatment of musculoskeletal pain: a comprehensive model. Man Ther 2009;14:531e8. Bishop MD, Bialosky JE, Cleland JA. Patient expectations of benefit from common interventions for low back pain and effects on outcome: secondary analysis of a clinical trial of manual therapy interventions. J Man Manip Ther 2011;19:20. Boyles RE, Ritland BM, Miracle BM, Barclay DM, Faul MS, Moore JH, et al. The shortterm effects of thoracic spine thrust manipulation on patients with shoulder impingement syndrome. Man Ther 2009;14:375e80. Chapman Dale, Newton M, Sacco P, Nosaka K. Greater muscle damage induced by fast versus slow velocity eccentric exercise. Int J Sports Med 2006;27:591e8. Chen Trevor C, Chen Hsin-Lian, Lin Ming-Ju, Wu Chang-Jun, Nosaka Kazunori. Muscle damage responses of the elbow flexors to four maximal eccentric exercise bouts performed every 4 weeks. Eur J Appl Physiol 2009;106:267e75. Chesterton Linda S, Sim Julius, Wright Christine C, Foster Nadine E. Interrater reliability of algometry in measuring pressure pain thresholds in healthy humans, using multiple raters. Clin J Pain 2007;23:760e6. Cheung Karoline, Hume Patria A, Maxwell Linda. Delayed onset muscle soreness: treatment strategies and performance factors. Sports Med 2003;33:145e64. Childs JD, Cleland JA, Elliott JM, Teyhen DS, Wainner RS, Whitman JM, et al. Neck pain: clinical practice guidelines linked to the international classification of functioning, disability, and health from the Orthopaedic Section of the American Physical Therapy Association. J Womens Health Phys Ther 2011;35:57. Clarkson Priscilla M, Hubal Monica J. Exercise-induced muscle damage in humans. Am J Phys Med Rehabil 2002;81:S52e69. Cook CE. Orthopedic manual therapy: an evidence based approach. Prentice-Hall; 2012. Cook Chad, Learman Ken, Houghton Steve, Showalter Christopher, OHalloran Bryan. The addition of cervical unilateral posterioreanterior mobilisation in the treatment of patients with shoulder impingement syndrome: a randomised clinical trial. Man Ther 2014;19:18e24. Coronado Rogelio A, Gay Charles W, Bialosky Joel E, Carnaby Giselle D, Bishop Mark D, George Steven Z. Changes in pain sensitivity following spinal manipulation: a systematic review and meta-analysis. J Electromyogr Kinesiol 2012;22:752e67. Dean Benjamin John Floyd, Gwilym Stephen Edward, Carr Andrew Jonathan. Why does my shoulder hurt? A review of the neuroanatomical and biochemical basis of shoulder pain. Br J Sports Med 2013;47:1095e104. Delitto A, George SZ, Van Dillen L, Whitman JM, Sowa G, Shekelle P, et al. Clinical practice guidelines linked to the international classification of functioning, disability, and health from the Orthopaedic Section of the American physical therapy Association. J Orthop Sports Phys Ther 2012;42:A1e57. ndez-De-Las-Pen ~ as C, Alonso-Blanco C, Cleland JA, Rodríguez-Blanco C, Ferna Alburquerque-Sendín F. Changes in pressure pain thresholds over C5eC6 zygapophyseal joint after a cervicothoracic junction manipulation in healthy subjects. J Manip Physiol Ther 2008;31:332e7. ndez-de-las-Pen ~ as C, Pe rez-de-Heredia M, Brea-Rivero M, MiangolarraFerna Page JC. Immediate effects on pressure pain threshold following a single cervical spine manipulation in healthy subjects. J Orthop Sports Phys Ther 2007;37:325. Flynn Timothy, Fritz Julie, Whitman Julie, Wainner Robert, Magel Jake, Rendeiro Daniel, et al. A clinical prediction rule for classifying patients with low back pain who demonstrate short-term improvement with spinal manipulation. Spine 2002;27:2835e43.
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Please cite this article in press as: Wassinger CA, et al., Cervical & thoracic manipulations: Acute effects upon pain pressure threshold and selfreported pain in experimentally induced shoulder pain, Manual Therapy (2015), http://dx.doi.org/10.1016/j.math.2015.08.009
Contents lists available at ScienceDirect
Manual Therapy journal homepage: www.elsevier.com/math
Original article
Cervical & thoracic manipulations: Acute effects upon pain pressure threshold and self-reported pain in experimentally induced shoulder pain Craig A. Wassinger a, *, Dustin Rich a, Nicholas Cameron a, Shelley Clark a, Scott Davenport a, Maranda Lingelbach a, Albert Smith a, G. David Baxter b, Joshua Davidson a a b
Department of Physical Therapy, East Tennessee State University, Johnson City, TN, USA School of Physiotherapy, University of Otago, Dunedin, New Zealand
a r t i c l e i n f o
a b s t r a c t
Article history: Received 9 April 2015 Received in revised form 8 July 2015 Accepted 18 August 2015
Background: Emerging evidence suggests that cervical and thoracic joint manipulations may be advocated in treating patients with shoulder pain. Objectives: To determine the acute effects of cervical, cervicothoracic, and thoracic joint manipulations on outcomes of self-reported pain and pain pressure threshold in experimentally induced shoulder pain. Design: Repeated measures. Methods: Twenty (20) healthy volunteers were tested on two sessions. Session 1 consisted on baseline assessment of pain pressure threshold testing over the infraspinatus bilaterally and self-reported shoulder pain using the shoulder pain and disability index (SPADI) pain scale. An isokinetic exercise protocol was used to induce delayed onset muscle soreness. In session 2 (24e48 h later), all variables were reassessed before and immediately after a combination of cervical, cervicothoracic and thoracic manipulations. Results: SPADI pain scale scores were significantly different between time points (p < 0.001): the exercise protocol significantly increased reported pain [mean increase 14.1, p < 0.001] while the manipulation significantly decreased reported pain (mean decrease 5.60, p < 0.001)) although pain remained higher than baseline levels. Pain pressure threshold differences were also found between time points (p ¼ 0.001): manipulation significantly increased pain threshold bilaterally (p < 0.001) similar to baseline levels. Conclusions: Cervical, cervicothoracic, and thoracic joint manipulations acutely increased pain pressure threshold and decreased self-reported shoulder pain in participants with experimentally induced shoulder pain. Physiotherapists may consider the combination of such techniques to achieve short-term hypoalgesic effects and facilitate the application of more active interventions. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Experimental shoulder pain Cervical and thoracic manipulation Manual therapy
1. Introduction Shoulder pain is among the most common pain location with point prevalence rates ranging from 7 to 26% in the general population (Luime et al., 2004). Given this, physical therapists have many interventions directed toward decreasing patients' complaints of shoulder pain including exercise, joint mobilization, and electrical and thermal modalities (Green et al., 2003).
* Corresponding author. Tel.: þ1 423 439 8295; fax: þ1 423 439 8077. E-mail address: [email protected] (C.A. Wassinger).
Manual therapy, specifically vertebral joint manipulation, is commonly utilized and advocated in treating a variety of musculoskeletal disorders (Flynn et al., 2002; Wainner et al., 2007; Iverson et al., 2008; Boyles et al., 2009; Mintken et al., 2010; Childs et al., 2011; Delitto et al., 2012). A recent systematic review has indicated that there is potential for benefit of shoulder conditions by treating the thoracic spine with manual therapy (Walser et al., 2009). The concept underlying this type of treatment has been described as regional interdependence, whereby impairments in one region can be linked, biomechanically and/or neurophysiologically, to impairments in neighboring anatomical regions (Wainner et al., 2007; Bialosky et al., 2009). Emerging evidence has
http://dx.doi.org/10.1016/j.math.2015.08.009 1356-689X/© 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Wassinger CA, et al., Cervical & thoracic manipulations: Acute effects upon pain pressure threshold and selfreported pain in experimentally induced shoulder pain, Manual Therapy (2015), http://dx.doi.org/10.1016/j.math.2015.08.009
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suggested utilizing spinal manual therapy to cervical and thoracic regions to treat patients with shoulder pain (Bergman et al., 2004; Boyles et al., 2009; Mintken et al., 2010; Muth et al., 2012). Reported benefits of spinal treatments for shoulder patients include increased pain free shoulder range of motion, decreased overall pain, improved self-reported function, and decreased provocative testing for shoulder injury (Mintken et al., 2010; Muth et al., 2012). One of the challenging aspects of treating shoulder pain is the range of pathoanatomical diagnoses that may be involved in pain origination (Dean et al., 2013). Unlike clinical practice, experimental pain models provide the opportunity for assessment of the efficacy of interventions on a reasonably uniform type of injury or painful condition (Staahl and Drewes, 2004). This study utilized an exercise induced delayed onset muscle soreness pain protocol. This method of simulating shoulder pain is appropriate given the pathophysiology and inflammatory changes created are similar to acute shoulder injury commonly found in younger individuals (Clarkson and Hubal, 2002; George et al., 2007). The aims of this paper were to determine the impact of cervical, cervicothoracic and thoracic manipulation on experimentally induced shoulder pain in a group of healthy young volunteers using both subjective selfreported pain measures and objective quantitative sensory testing (pain pressure threshold). 2. Methods 2.1. Participants A sample of convenience consisting of healthy volunteers participated in this study. Participants were between the ages of 23 and 27 years. This age group was specifically chosen to decrease the likelihood of age related degeneration of the shoulder muscles (Milgrom et al., 1995). Participants were considered healthy using the following criteria: denied any history seeking medical care for shoulder or neck injuries, and reported no current (past 6 months) shoulder or neck pain. Exclusion criteria consisted of prior shoulder surgery or fracture, and contraindication to cervical or thoracic manipulation as determined by medical screening from the principal investigator (CAW) (Cook, 2012). Participants were not seeking treatment for any other musculoskeletal disorder either. All testing was completed in a University research laboratory using procedures approved by the East Tennessee State University Institutional Review Board. All participants provided informed consent as per University guidelines. Equal numbers of males and females were recruited as differences have been noted in pain reporting between genders (Stohler et al., 2001). 2.2. Study design A repeated measures design was employed in this project with testing occurring in 2 sessions completed on separate days (Fig. 1). The first testing session consisted of screening for vertebrobasilar insufficiency (VBI), baseline outcome measures [self-reports shoulder pain (shoulder pain and disability index (SPADI) pain scale only); pain pressure threshold], maximal isometric shoulder strength in a modified neutral position, and completion of a standardized eccentric exercise protocol designed to induce shoulder pain via delayed onset muscle soreness (Chapman et al., 2006; Chen et al., 2009). Participants returned for day 2 of testing 24e48 h after the first session as peak soreness has been reported to occur between 24 and 72 h post exercise. They were asked not to exercise their upper body or utilize any treatments (ice, Non-steroidal anti-inflammatory drugs (NSAIDs), etc.) to reduce the shoulder pain. Day 2 testing consisted of repeated outcome measures, collected as noted (Cheung et al., 2003) above, VBI screening,
Fig. 1. Participant testing outline.
and the application of cervical and thoracic manipulations. The acute effects of the manipulations were then measured again using the outcomes described. Specific details on all procedures are described below. 2.3. Outcome measures The self-reported questionnaire used in our study was the SPADI pain scale, which comprises 5 questions referring to the severity of pain experienced in the shoulder. The entire SPADI includes a selfreported disability scale and a self-reported pain scale. The disability scale was not used in this investigation. The entire SPADI has been shown to demonstrate acceptable reliability, internal consistency, validity and responsiveness (Roy et al., 2009). Total score ranges from 0 to 50, with 0 as no pain and 50 as the highest pain score. If there was any presence of pain at baseline (a score other than 0) or if there was no change in SPADI score from baseline, meaning no presence of experimental pain, then the participant was excluded from further testing. Pain pressure threshold is the minimal amount of pressure required for the sense of pressure to change to pain (Nussbaum and Downes, 1998). A digital algometer (Wagner, Pain Test FP Algometer, Greenwich, CT) with a 1 cm2 blunt tip was used for testing. Pain pressure threshold was tested over the infraspinatus muscle belly with the participant in prone in the anatomical position. Testing occurred bilaterally as means to determine the systemic effects of the manipulations. The infraspinatus muscle belly was located by palpation inferior to the approximate midpoint of the scapular spine (Fig. 2). When the participant appreciated the vertical force as pain the algometer was removed and the peak force recorded. Standardized procedures for use of the pressure algometer were performed by the same investigator for all measures, with the average of three measurements used for analysis (Nussbaum and Downes, 1998). The time between pain pressure threshold measures was not standardized. Training on pain pressure threshold measurement procedures was performed prior to initiation of the study. 2.4. Experimental pain protocol Following collection of baseline outcome measurements, participants performed a concentric/eccentric exercise protocol on the
Please cite this article in press as: Wassinger CA, et al., Cervical & thoracic manipulations: Acute effects upon pain pressure threshold and selfreported pain in experimentally induced shoulder pain, Manual Therapy (2015), http://dx.doi.org/10.1016/j.math.2015.08.009
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screening for manual interventions targeting the cervical spine. The screening performed included sustained rotation of the cervical spine for 10 s, followed by 10 s in neutral. This was then performed to the contralateral side (Magarey et al., 2004; Arnold et al., 2004). Further, a premanipulative hold was sustained for 10 s in the treatment position with an additional 10 s assessment in neutral to determine if any delayed effects were present (Arnold et al., 2004). 2.6. Interventions
Fig. 2. Pain pressure testing participant position.
non-dominant (non-throwing) shoulder using an isokinetic dynamometer (HUMAC Norm Isokinetic Dynamometer, Computer Sports Medicine Institute, Stoughton, MA). This protocol was designed to induce delayed onset muscle soreness of the external rotators as the experimental shoulder pain condition (Chapman et al., 2006; Chen et al., 2009). The exercise protocol consisted of 3 sets of 30 repetitions of concentric external rotation at 60 / s followed by an eccentric return at 300 /s in a modified neutral position (Fig. 3). The dynamometer was set to move through a 50 arc of motion (25 internal and external rotation from neutral). External rotation isometric strength testing was performed prior to and immediately following the exercise protocol. Participants whose strength had not decreased by more than 50% from the baseline strength measurement were required to complete additional sets of 30 repetitions until the required 50% reduction in strength was achieved (George et al., 2007).
2.5. VBI screening VBI screening was performed twice as part of the study protocol. The initial test was to determine eligibility based on the inclusion/ exclusion criteria. The second administration was included in accordance with published guidelines on premanipulative
All participants received high velocity low amplitude (HVLA) thrust manipulation to their cervical spine, cervicothoracic region, and thoracic spine (Fig. 4). The targeted spinal levels for the cervical spine were C5, C6, and C7 utilizing a cervical lateral thrust technique with the force directed toward the contralateral eye ndez-de-las-Pen ~ as et al., 2007; Ruiz-Sa ez et al., 2007). HVLA (Ferna were performed at each segment until cavitation was noted by the participant or investigator for up to 2 attempts. If no cavitation was noted after 2 attempts, the investigator moved on to the more distal segment (Boyles et al., 2009). The same guidelines for treatment were applied to all interventions performed. Following cervical spine treatments the cervicothoracic region was treated using a distractive technique (Boyles et al., 2009; Mintken et al., 2010). Finally, a prone extension biased posterior to anterior technique was performed at the apex of the thoracic kyphosis, and to the proximal and distal 2 segments for a total of 5 targeted interventions in the thoracic spine. The segments for manipulation in the cervicothoracic and thoracic spine were included to be consistent with prior related investigations for shoulder disorders (Boyles et al., 2009; Mintken et al., 2010). Cervical levels C5eC7 were also chosen based on prior reports of non-thrust manual therapy for shoulder disorders (Mintken et al., 2010) and as the nerve root levels (C5eC6) for the suprascapular nerve (infraspinatus innervation). 2.7. Data analysis Repeated measures analyses of variance (ANOVA) were used to compare SPADI pain scores between baseline, pre-manipulative, and post-manipulative time points (SPSS Inc., Chicago, IL). Furthermore, a two-way ANOVA was used to evaluate change in pressure pain threshold with side (dominant, non-dominant) as the between-subjects factor and time (baseline, pre-manipulation and post-manipulation) as within subject factors. If the Mauchly sphericity test was statistically significant, degrees of freedom were corrected using the GreenhouseeGeisser method. Post hoc paired t-tests were used as appropriate. Significance was set at p 0.05. Effect sizes (ES) were also calculated using the effect size index [(pre-manipulative score post-manipulative score)/standard deviation pre-manipulative score]. Further, intraclass correlation coefficient (ICC3,1) and standard error of measurement (SEM) were calculated to assess reliability of pain pressure threshold data using the 3 trials from the baseline measurement. 3. Results
Fig. 3. Isokinetic setup.
Twenty-three participants completed day one of testing. Of these, twenty participants were able to complete day two of testing and, therefore, were included in data analysis (Table 1). Of the three participants excluded after testing day one, two subjects did not report any pain as of the SPADI after day one, and the third participant was excluded because of equipment malfunction. All participants were negative for VBI based on our screening. Baseline SPADI pain scores were 0 for all participants. SPADI pain scores were significantly different between time points
Please cite this article in press as: Wassinger CA, et al., Cervical & thoracic manipulations: Acute effects upon pain pressure threshold and selfreported pain in experimentally induced shoulder pain, Manual Therapy (2015), http://dx.doi.org/10.1016/j.math.2015.08.009
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Fig. 4. Cervical, cervicothoracic, and thoracic manipulations.
Table 1 Demographic data.
Males Females
Participants
Age (years)
Weight (kg)
Height (cm)
Right hand dominance
Baseline SPADI pain scale scores
10 10
24.8 ± 1.2 24.4 ± 1.8
84.1 ± 16.4 64.8 ± 11.6
179.3 ± 6.4 165.1 ± 6.6
8 9
0.0 ± 0.0 0.0 ± 0.0
Values are expressed as mean ± standard deviation.
(p < 0.001). Post hoc testing revealed the exercise protocol significantly increased reported pain [mean increase 14.1, p < 0.001]. The manipulation protocol significantly decreased reported pain (mean decrease 5.60, p < 0.001, ES ¼ 1.24); however pain remained higher than baseline levels (mean difference 8.50, p < 0.001). Reliability of pain pressure threshold testing was shown to be acceptable with ICC ¼ 0.985 (95% CI: 0.994e0.969) and a SEM ¼ 0.453 kg/cm2. No interaction (side time point) was found (F ¼ 0.208, p ¼ 0.761). However, the main effect of time point was significant (F ¼ 9.659, p ¼ 0.001), thus differences existed between baseline, pre-manipulation, and post-manipulation. Post hoc testing revealed pain pressure threshold values did not differ between baseline and pre-manipulative time points for dominant (p ¼ 0.556) and non-dominant (p ¼ 0.160) sides. Manipulation significantly increased pain pressure threshold bilaterally (dominant p < 0.001) and non-dominant (P < 0.001) (Table 2), yet these values were not significantly higher than baseline values (dominant p < 0.072) and non-dominant (P < 0.157). The increase in pain pressure threshold following manipulation represents an average increase in pain threshold by 25%. The effect size of the manipulation was near 0.40 bilaterally thus indicating a moderate change has occurred. 4. Discussion This study measured the effect of cervical, cervicothoracic and thoracic manipulation on 2 measures of pain, a self-reported measure of shoulder pain related to severity and function, and an objective measure of pain pressure threshold. Both measures
of pain were found to significantly improve immediately following manipulations with moderate to large effect sizes noted. These findings indicate spinal manipulation has an immediate local and systemic hypoalgesic effect on shoulder pain induced by delayed onset muscle soreness. The increase in pain threshold was approximately 25% bilaterally with moderate effects sizes near 0.4. Increases in pain pressure threshold greater than 15% have been reported to be clinically meaningful (Chesterton et al., 2007). Thus, both statistical and clinically significant changes in pain pressure threshold were noted immediately following the manipulations performed in this study. The increased pain pressure threshold findings are in accordance with conclusions from recent systematic reviews (Coronado et al., 2012; Voogt et al., 2014). A unique aspect of this study was the measurement of selfreported pain changes immediately following the manipulations, in addition to pain pressure threshold. The SPADI pain scale questions addressed pain severity and pain during functional activities. Cervical, cervicothoracic and thoracic manipulation was shown to be of significant benefit to participants' self-reported pain. The minimal clinically important difference of the entire SPADI (pain and disability scales) has been reported to be 8 points (Roy et al., 2009). Interpretations of the pain scale in isolation are difficult, yet the mean increase in pain scores from 0 to 14.1 indicate the exercise protocol was able to impart a clinically relevant painful condition. However, the acute effects of the manipulations decreased the mean self-reported pain by 5.6 points; therefore, the clinical significance of the reported pain decrease (i.e. in isolation) is more difficult to interpret. Given the high effect size, this
Table 2 Pain pressure threshold (PPT) outcomes. Mean (standard deviation)
Baseline PPT Pre-manipulation PPT Post-manipulation PPT
Dom
ND
5.73 (3.60) 5.46 (3.20) 6.69 (3.31)
5.67 (3.61) 5.02 (3.19) 6.41 (3.14)
Mean side-to-side difference
Mean time point difference (% change)
Effect size
0.06 0.44 0.28
Dom 0.27 (4.7) 1.23 (22.5)
Dom 0.07 0.38
ND 0.65 (11.5) 1.39 (27.7)
ND 0.18 0.44
Dom: Dominant, ND: Non-Dominant. All values in kilograms/cm2, % change ¼ time point difference/starting time point value 100%.
Please cite this article in press as: Wassinger CA, et al., Cervical & thoracic manipulations: Acute effects upon pain pressure threshold and selfreported pain in experimentally induced shoulder pain, Manual Therapy (2015), http://dx.doi.org/10.1016/j.math.2015.08.009
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indicates a strong relationship between the decreased shoulder pain and the manipulations. A similar positive effect on self-reported pain and function in patients seeking treatment for shoulder injury has been shown in prior studies over in the short term (2e3 days) (Boyles et al., 2009; Mintken et al., 2010). The results from the current study and prior investigations indicate there is a potential benefit of spinal manual therapy for patients with shoulder pain with acute and short term follow up (Boyles et al., 2009; Mintken et al., 2010; Muth et al., 2012); in contrast, longer term outcomes have been mixed (Winters et al., 1997; Bergman et al., 2004; Savolainen et al., 2004; Cook et al., 2014). Wide variability in shoulder conditions, treatment types, follow-up period, and outcome measures makes direct comparison of previous results difficult. Some prior studies have shown long term (11e52 weeks) improvement in shoulder pain when comparing spinal manual treatment to NSAID's, exercise, massage, and modalities (Bergman et al., 2004; Savolainen et al., 2004), while other studies (Winters et al., 1997; Cook et al., 2014) have shown equivocal or mixed results. The main limitation of most of the long-term studies is that the interventions used (manipulation only versus exercise, modalities and massage) did not represent standard clinical practice. In routine clinical practice, a multimodal approach including exercise, manual therapy, and additional thermal or electrical modalities are utilized to treat shoulder pain (Michener et al., 2004; Tate et al., 2010; Cook et al., 2014). In line with this, a recent trial by Cook et al. (2014) found no differences in reported outcomes between groups when spinal manual treatments (Grade III mobilizations) were added to usual care (exercises, modalities, etc.). The intervention combinations (manual therapy plus exercise) used in the trial by Cook et al. (2014) likely best represent standard physical therapy treatment for shoulder pain. Contrary to our study however, they used a lower grade spinal manual treatment (Grade III mobilizations versus manipulation) on shoulder impingement patients; thus direct comparisons are difficult. Although the mechanisms underlying the positive effect of the applied intervention were not addressed directly in this study, some discussion is warranted. It is possible that both segmentally mediated and central inhibitory mechanisms were responsible for the pain changes found in this study. Vertebral joint stimulation at the associated nerve roots of the shoulder muscles and scapula (C5T2) may affect the pain pressure threshold over infraspinatus bilaterally as well as reported pain at the shoulder. Segmental inhibition may have occurred due to stimulation of large diameter low-threshold mechanoreceptors (Katavich, 1998). Additionally, the spinal manipulations may have created a stimulus to activate the descending inhibitory pain systems such as autonomic and opioid systems (Vicenzino et al., 1998, 2001; Skyba et al., 2003). Any one or a combination of the above mentioned mechanisms may have played a role in the observed effects of bilaterally decreased pain pressure threshold and self-reported pain. There are some limitations to our study which should be noted. First, the participants in this study were healthy volunteers with experimentally induced mild muscle pain. The response of shoulder patients with a variety of conditions (specifically nonmusculotendinous injuries), and higher pain levels, may differ from the outcomes reported here. However, prior studies have shown positive effects for shoulder pain patients with manipulation (Boyles et al., 2009; Mintken et al., 2010; Tate et al., 2010; Muth et al., 2012). Secondly, no comparison group (sham intervention or control) was included for comparison. Prior investigations however, have shown no effect of sham or control on pain pressure ndez-de-las-Pen ~ as threshold variable on healthy participants (Ferna ~ as et al., 2008). Finally, it is et al., 2007; Fern andez-De-Las-Pen possible that the act of manipulation, including the noise, created
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during the manipulations created a placebo effect (Bishop et al., 2011); this would be difficult to quantify and was beyond the scope of this study. 5. Conclusions This study demonstrated clinically significant acute pain reduction in participants with experimentally induced shoulder pain following spinal manipulation. The use of cervical, cervicothoracic and thoracic manipulation may be considered an appropriate intervention by physical therapists treating patients with painful shoulder conditions, where such treatments are otherwise not contraindicated. The acute decreases in pain following manipulation may allow more aggressive participation in a standard multimodal treatment approach including active exercise, selective stretching, and functional retraining earlier in the rehabilitation process. References Arnold C, Bourassa R, Langer T, Stoneham G. Doppler studies evaluating the effect of a physical therapy screening protocol on vertebral artery blood flow. Man Ther 2004;9:13e21. Bergman GJD, Winters JC, Groenier KH, Pool JJM, Jong BM, Postema K, et al. Manipulative therapy in addition to usual medical care for patients with shoulder dysfunction and pain. Ann Intern Med 2004;141:432. Bialosky JE, Bishop MD, Price DD, Robinson ME, George SZ. The mechanisms of manual therapy in the treatment of musculoskeletal pain: a comprehensive model. Man Ther 2009;14:531e8. Bishop MD, Bialosky JE, Cleland JA. Patient expectations of benefit from common interventions for low back pain and effects on outcome: secondary analysis of a clinical trial of manual therapy interventions. J Man Manip Ther 2011;19:20. Boyles RE, Ritland BM, Miracle BM, Barclay DM, Faul MS, Moore JH, et al. The shortterm effects of thoracic spine thrust manipulation on patients with shoulder impingement syndrome. Man Ther 2009;14:375e80. Chapman Dale, Newton M, Sacco P, Nosaka K. Greater muscle damage induced by fast versus slow velocity eccentric exercise. Int J Sports Med 2006;27:591e8. Chen Trevor C, Chen Hsin-Lian, Lin Ming-Ju, Wu Chang-Jun, Nosaka Kazunori. Muscle damage responses of the elbow flexors to four maximal eccentric exercise bouts performed every 4 weeks. Eur J Appl Physiol 2009;106:267e75. Chesterton Linda S, Sim Julius, Wright Christine C, Foster Nadine E. Interrater reliability of algometry in measuring pressure pain thresholds in healthy humans, using multiple raters. Clin J Pain 2007;23:760e6. Cheung Karoline, Hume Patria A, Maxwell Linda. Delayed onset muscle soreness: treatment strategies and performance factors. Sports Med 2003;33:145e64. Childs JD, Cleland JA, Elliott JM, Teyhen DS, Wainner RS, Whitman JM, et al. Neck pain: clinical practice guidelines linked to the international classification of functioning, disability, and health from the Orthopaedic Section of the American Physical Therapy Association. J Womens Health Phys Ther 2011;35:57. Clarkson Priscilla M, Hubal Monica J. Exercise-induced muscle damage in humans. Am J Phys Med Rehabil 2002;81:S52e69. Cook CE. Orthopedic manual therapy: an evidence based approach. Prentice-Hall; 2012. Cook Chad, Learman Ken, Houghton Steve, Showalter Christopher, OHalloran Bryan. The addition of cervical unilateral posterioreanterior mobilisation in the treatment of patients with shoulder impingement syndrome: a randomised clinical trial. Man Ther 2014;19:18e24. Coronado Rogelio A, Gay Charles W, Bialosky Joel E, Carnaby Giselle D, Bishop Mark D, George Steven Z. Changes in pain sensitivity following spinal manipulation: a systematic review and meta-analysis. J Electromyogr Kinesiol 2012;22:752e67. Dean Benjamin John Floyd, Gwilym Stephen Edward, Carr Andrew Jonathan. Why does my shoulder hurt? A review of the neuroanatomical and biochemical basis of shoulder pain. Br J Sports Med 2013;47:1095e104. Delitto A, George SZ, Van Dillen L, Whitman JM, Sowa G, Shekelle P, et al. Clinical practice guidelines linked to the international classification of functioning, disability, and health from the Orthopaedic Section of the American physical therapy Association. J Orthop Sports Phys Ther 2012;42:A1e57. ndez-De-Las-Pen ~ as C, Alonso-Blanco C, Cleland JA, Rodríguez-Blanco C, Ferna Alburquerque-Sendín F. Changes in pressure pain thresholds over C5eC6 zygapophyseal joint after a cervicothoracic junction manipulation in healthy subjects. J Manip Physiol Ther 2008;31:332e7. ndez-de-las-Pen ~ as C, Pe rez-de-Heredia M, Brea-Rivero M, MiangolarraFerna Page JC. Immediate effects on pressure pain threshold following a single cervical spine manipulation in healthy subjects. J Orthop Sports Phys Ther 2007;37:325. Flynn Timothy, Fritz Julie, Whitman Julie, Wainner Robert, Magel Jake, Rendeiro Daniel, et al. A clinical prediction rule for classifying patients with low back pain who demonstrate short-term improvement with spinal manipulation. Spine 2002;27:2835e43.
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Please cite this article in press as: Wassinger CA, et al., Cervical & thoracic manipulations: Acute effects upon pain pressure threshold and selfreported pain in experimentally induced shoulder pain, Manual Therapy (2015), http://dx.doi.org/10.1016/j.math.2015.08.009