Mr Perreault is Head Athletic Trainer, U.S. Mens Alpine Ski Team, United States Ski and Snowboard Association, Park City, Utah, Dr Kelln is from the Naval Health Clinic Hawaii, Pearl Harbor, Hawaii, Dr Hertel, Ms Pugh, and Dr Saliba are from the University of Virginia, Charlottesville, Va.
The authors have no financial or proprietary interest in the materials presented herein.
The views expressed in this article are those of the authors and do not reflect the official policy of the Department of the Navy, the Department of Defense, nor the United States Government.
Address correspondence to Susan Saliba, PhD, ATC, PT, Human Services, University of Virginia, PO Box 400407, Charlottesville, VA 22904; e-mail email@example.com.
Approximately 23 million people (close to 10% of the U.S. population) suffer from chronic musculoskeletal disorders.1 Myofascial pain is estimated to account for 85% of muscular pain due to injury and 90% of patients treated in pain clinics at a cost of $47 billion U.S. dollars per year.2 Manual therapy is often sought as an appealing intervention, but few data substantiate its short- or long-term use. Many individuals prefer massage and alternative treatments over pharmacological intervention for chronic pain, especially when the discomfort is less severe.3 Furthermore, many healthy people experience occasional muscle tightness and pain that may be treated with manual therapy. Strain counterstrain (SCS) is a manual therapy intervention used for the treatment of myofascial pain and has been proposed to interrupt muscle spasm.
Strain counterstrain attempts to place the painful area in a position of comfort to alleviate tension and pain. The mechanism of relief is thought to occur from the involvement of a combination of neurological and circulatory changes in the distressed area when placed in its most comfortable position.4,5 The physiological mechanism for SCS is unknown but has been hypothesized to occur from a change in the muscle spindle activity. For example, a strain occurs from the muscle spindle activity, or gamma gain, and is produced by the rate of firing from the annulospiral nerve endings when the muscle is overstretched.6 The muscle spindle sensitivity increases as a protective measure by increasing the gamma gain in the overstretched position. Other muscles that support the joint are in a shortened position and have less spindle activity at rest. However, once the joint is moved, the muscle spindles react to the new position by increasing tension. The shortened muscle creates resistance to movement and ultimately results in somatic dysfunction or pathology to the musculoskeletal system.7 The aberrant gamma gain is likely due to local reflexogenic activity.8
Jones6 explained that the somatic dysfunction is not caused from the strain, but from the body’s reaction to the strain. The reaction is termed the counterstrain and results in a shortening of intrafusal fibers, leading to an oversensitized muscle spindle.8 If the counterstrain is slow and deliberate, the somatic dysfunction is avoided. If the reaction is rapid, as in a functional movement, a reflex muscle spasm occurs, creating the dysfunction.6,9,10 The muscle position must be reset to rectify the sensitized muscle spindle. The position is held to reprogram the muscle spindle and allow the afferent activity to normalize. Once the muscle spindle has accommodated to the new position, the shortened muscle no longer resists movement and function is restored.
In the current literature, there are surprisingly few articles that address the efficacy of manual therapies and fewer that discuss SCS as a treatment. In 1994, a review of treatments for myofascial pain syndrome treatments revealed that no reported treatment was more effective than the control intervention.11 In 2005, a second review of myofascial trigger point treatments concluded that previous findings could neither be confirmed nor refuted due to the lack of research in this area and a lack of reliable and valid outcome measures.12 Investigations on the effects of SCS specifically use a variety of treatment positions13,14 and patient diagnoses,14–17 making comparisons difficult.
Tender points are defined as small zones of localized tenderness in muscle, the muscle tendon junction, fat pad, or bursal region.14,18–21 Tender points are described as focal areas of tightness, pain, or hypersensitivity and are considered to be the pathological condition that can be treated with SCS.6 Tender points, as described by Jones,6,10 are considered more segmental than trigger points. Tender points located along the vertebral column designate segmental dysfunction at the corresponding vertebral level and can be a sensory manifestation of a neuromuscular or musculoskeletal dysfunction.6 However, from a clinical perspective, it is difficult to distinguish tender points from myofascial trigger points. Studies that examine the ability to reliably categorize the points have been inconclusive, even with experienced clinicians.21,22
There are many treatments aimed to release muscle tension, tightness, and tender or trigger point pain. Current trends include the use of tricyclic antidepressants, muscle relaxants, trigger point injections, mild analgesics, and nonsteroidal anti-inflammatory drugs.23 There are several manual therapies used to trigger tender points, including ischemic compression, spray and stretch, muscle energy techniques, trigger point pressure release, transverse friction massage, and SCS.12 Because there is a lack of evidence supporting many treatment options, the goal of this study was to evaluate the use of SCS on upper trapezius discomfort in a convenience sample of otherwise healthy individuals. Our purpose was to compare the effectiveness of a single intervention of SCS to a sham treatment both immediately following the treatment and 24 hours later. We hypothesized that the SCS group would have superior pain relief compared to the sham treatment. A secondary goal was to establish a methodology that could translate into future studies so that manual therapy outcomes could be compared. This pilot data would be used to develop a more extensive research plan that would involve SCS as part of a comprehensive treatment program for the management of upper trapezius pain.
The study was a double-blinded, randomized control trial of participants with self-reported complaints of upper trapezius stiffness, pain, or tightness. Participants were randomly assigned to either an experimental group receiving a SCS treatment or a control group receiving a sham treatment. To test the effects of the treatment over time, pain measurement was conducted pretreatment, immediately posttreatment, and 24 hours posttreatment. The dependent variables were resting pain measured using a visual analogue scale, pain threshold, and provoked pain.
Twenty participants (11 men, 9 women, mean age, 22.4±2.6 years; mean height, 172.4±9.75 cm; mean mass, 74.99±14.33 kg) with self-reported upper trapezius tightness and pain volunteered to participate in this study. This convenience sample was recruited from the general student body and faculty of a military college. Participants were otherwise healthy and had no previous knowledge of SCS. The university’s board for health sciences approved the study methods. All participants read and signed an informed consent agreement prior to participating in the study.
A pressure algometer (Model PTH, Pain Diagnostics and Treatment, Inc., Great Neck, NY) was used in this study to measure the amount of pressure applied to an area 1 cm2 in surface area. The algometer measured pressures ranging from 0–10 kg/cm2 in 0.1-kg/cm2 increments. After measuring resting pain, we used the algometer to measure the pressure that would evoke a pain response (pain threshold). We then used the algometer to apply a constant pressure to measure the sensitivity of the tender point. For this measurement, the algometer was applied to the upper trapezius tender point to provoke the pain response that was measured using a visual analogue scale (provoked pain). Several studies have reported this type of algometer to be reliable when measuring the sensitivity of a variety of trigger points.24–28 Nussbaum and Downes28 reported excellent same-day intratester reliability (intraclass correlation coefficient ([ICC]2,1 = 0.93–0.98) and excellent day-to-day intra-tester reliability (ICC2,1 = 0.88–0.90) when used on upper trapezius trigger points.24 The algometer has been used as an important assessment tool in past research evaluating the effectiveness of trigger point therapy.23,28
The visual analogue scale (VAS) was used as a tool to measure pain. The VAS has been reported to be a valid and reliable measurement of pain intensity.29,30 We used the VAS to measure resting pain and pain during the provocation maneuver with a predetermined pressure application from the algometer.
Participants responded to flyers posted around campus to recruit individuals with chronic muscle pain or tightness in the upper trapezius region. Potential participants were prescreened over the phone for injuries and other exclusion criteria. A certified athletic trainer confirmed the presence of palpable tenderness or focal tightness in the upper trapezius musculature associated with either a trigger or tender point and administered a health history questionnaire. The pain had to be present for at least 1 week and could not be alleviated with stretching. We avoided rigorous palpation of the treatment area during the evaluation because manipulation of the area, including inducing a twitch response, might influence the outcome.31 Participants were excluded from the study if they reported that they had recent acute cervical or shoulder trauma, facet joint pathologies in the cervical spine, and a history of thoracic outlet syndrome, fibromyalgia, or myofascial pain syndrome. Specific details of each type of pathology were described in the questionnaire and over the phone so participants would understand and be able to report if they had one of these conditions. Furthermore, participants were asked to report whether they were receiving any other medical care for any existing condition that would affect their continuation in the study. All 20 participants met the inclusion criteria and were enrolled in the study.
Participants were placed in a treatment group (SCS or sham) using random allocations enclosed in sealed envelopes. The group assignment was blinded to both the participant and the assessing clinician; only the treating clinician was aware of the group assignment. The treating clinician placed the algometer over the most sensitive point and marked the participant’s skin around the rod of the algometer with a black felt-tipped permanent marker so that the location could be correctly identified by the assessing clinician and would remain marked the following day.
The assessing clinician performed all measurements and was unaware of the treatment condition. He instructed the participant to record a quiet VAS to assess resting pain. Participants were shown a 10-cm nondemarcated line and were asked to mark a vertical line along the line corresponding with the level of pain they were experiencing in the tender point at that moment. Next, the examiner measured pain threshold. He applied pressure over the marked area with the algometer at a rate of 1 kg/sec until the participant reported the first onset of pain. At that time, the examiner released the pressure and read and recorded the value as the baseline pain threshold score. Finally, a provoked VAS was taken by applying a predetermined force that was slightly more than what has been found in the literature as the normal values for pain threshold of the upper trapezius. Fischer et al32 found the normal pain thresholds of the upper trapezius to be 4.8 kg/cm2 of pressure for men and 3.3 kg/cm2 of pressure for women. We added 0.7 kg of force to each value to provoke enough pain to minimize the possibility of a floor effect (ie, when the pain scores are already low, making it potentially impossible to go lower with any kind of treatment) during our analysis. Male participants received a force of 5.5 kg/cm2, and female participants received 4.0 kg/cm2. Depending on group assignment, the participant then received the experimental or sham treatment, performed by the treating clinician when the assessing clinician was out of the room.
The SCS group received the SCS intervention as described by Jones9,10 and was applied by a clinician who was trained in the Jones technique. Strain counterstrain is a very individualized treatment and all participants were placed in a position that alleviated most of their pain. The upper trapezius was placed in a position of comfortable shortening, while the participant noted a subjective decrease in tenderness with palpation over the tender point (Figure 1). The head was passively laterally flexed to the ipsilateral side and rotated away. Then the shoulder was flexed to approximately 150 to 170 degrees and the relative position of internal or external rotation was adjusted to comfort. None of the motions were at the end range, and adjustments were made according to participant feedback. This position was held for 90 seconds, and then the participant was slowly and passively returned to a normal resting position.
Figure 1. The Position of the Strain Counterstrain Treatment for the Right Upper Trapezius. The Head Is Laterally Flexed to the Ipsilateral Side and Rotated Away While the Tender Point Is Palpated. The Shoulder Is Passively Moved into Flexion and Relative External Rotation According to Feedback from the Subject.
The sham treatment consisted of the clinician placing his hands on the upper trapezius and on the head, contralateral to the side of the tender point and, holding this position for 90 seconds (Figure 2). The head was turned slightly, and there was minimal pressure applied to the tender point with an open palm to prevent a treatment effect with the sham condition. After either treatment, the same measurements were taken by the assessing clinician, as described earlier. The participant was dismissed for the day and asked to refrain from any strenuous activities, drinking alcohol in excess, and taking analgesics or non-steroidal anti-inflammatory drugs.
Figure 2. The Position of the Sham Treatment for the Upper Trapezius. The Head Is Gently Positioned Without Reaching Any Restriction in the Tissues. There Is a Laying of the Hands in a Broad Manner on the Upper Trapezius and on the Head.
Participants reported for a follow-up assessment 24 hours after the treatment. The examiner repeated the steps taken after the treatment on the first day, measuring the resting pain, pain threshold, and provoked pain. All participants completed all components of the study.
General linear model analyses of variance (ANOVAs) were used to compare group by time interactions with repeated measures for the three dependent variables (resting pain, pain threshold, and provoked pain). For each measure, a 2χ3 repeated measures ANOVA was used to compare group (SCS, sham) and time (baseline, immediate posttreatment, 24 hours posttreatment). The alpha level was set a priori at P < 0.05 and SPSS version 13.0 software (SPSS Inc, Chicago, Ill) was used for all analyses. Sample size was estimated using an effect size of 0.80, which was obtained from means and standard deviations from a previous study examining the effect of SCS on tender point pain.13 Based on these calculations, it was estimated that 10 participants per group would be necessary to have an 80% chance (ß) of detecting a significant change in muscle activation with an a priori alpha level of P ≤ .05.
Means and standard deviations for measurements are reported in the Table. For resting pain, there was a significant time main effect (F18,1 = 7.04, P = .003) (Figure 3), with both treatments associated with decreased pain from baseline to the 24-hour assessment. There was no significance for the group by time interaction (F18,1 = 0.281, P = .757), or group main effect (F18,1 = .895, P = .357) for the resting pain (1-ß = 0.091). Effect sizes were calculated with Cohen’s d, and there was a large effect size for the SCS (0.71), moderate for sham treatments (0.4) for immediate resting pain, and large effect sizes for SCS (0.85) and sham (0.97) for resting pain at 24 hours posttreatment.
Table: Means and Standard Deviations of Measurements
Figure 3. Resting Pain Scores. Results for Pain at Rest on the Vas Scale. There Was a Significant Main Effect (*) for Time (p = .003) Indicating that Both Groups Improved After Intervention. There Was not a Significant Group Main Effect or Group by Time Interaction.
For the pain threshold measure, there was no significant time main effect (F18,1 = 1.929, P = .16) (1 − ß = 0.374) (Figure 4), group by time interaction (F18,1 = .269, P = .766) (1 − ß = 0.089), or group main effect (F18,1 = .767, P = .393) (1-ß = 0.132). There were negligible effect sizes for all pain threshold measurements.
Figure 4. Pain Threshold Scores. There Were No Significant Findings for the Pain Threshold Measures.
Similarly for provoked pain, there was no significant time main effect (F18,1 = 2.286, P = .116) (1-ß = 0.434) (Figure 5), group by time interaction (F18,1 = 1.214, P = .309) (1-ß = 0.248), or group main effect (F18,1 = 1.26, P = .276) (1-ß = 0.186). The effect sizes for the provoked pain were small to negligible for the SCS (0.17) and sham (0.05) immediately after the treatment and small 24 hours later for both SCS (0.24) and control (0.30).
Figure 5. Provoked Pain Scores. There Were No Significant Findings for the Provoked Pain Measures. Abbreviations: Vas, Visual Analogue Scale; SCS, Strain Counterstrain.
There were no significant differences found between the single 90-second SCS treatment and the sham treatment for pain at rest, pain threshold, or provoked pain in this pilot study. Although a main effect was found for resting pain over time, there was not a significant interaction between the groups. These results indicate that the participants experienced a perceived treatment effect for resting pain measures regardless of group assignment.
We hypothesized that the SCS treatment would result in a significant reduction in pain. Although our results offer no support for the use of SCS over a placebo treatment, we offer several explanations for our results. Our participants self-reported the presence of upper trapezius pain and tightness, but they were not seeking medical treatments for their pain. The mean (±SD) baseline resting pain values were low and potentially subclinical (1.2±1.4; mean ± SD). These values are in contrast to Lee et al33 who reported resting VAS scores of 5.3±1.95 in patients with upper trapezius trigger points who were recruited from physician referrals. We believe this may have had a floor effect on our data given that it would have been unlikely to improve the pain value from a clinical perspective. Clearly, patient referrals should be used for participant recruitment. However, both treatment groups reported a significant reduction in resting pain over time.
Another potential explanation of our results is that the SCS treatment group received only one treatment application at the single tender point. This method was to ensure consistency from one participant to another; however, a full SCS treatment may require up to three or four repeated applications during one treatment. The effect sizes indicate that participants reported improvements in both resting pain and provoked pain immediately and at 24 hours after either the SCS or sham treatment. Perhaps the attention to the pain and “laying of hands” involved in both the treatment and sham conditions contributed to these results, indicating that SCS was as effective as a placebo. However, other studies found positive treatment effects using a single exposure to SCS.14,15
To evaluate the sensitivity of the tender points, we applied pressure to them. In a previous study assessing the reliability of the algometer, Reeves et al27 noted that repeated application of pressure above the pain threshold altered the sensitivity of the tissue, confounding the measurement process. The assessment of our outcome measures had the potential for altering the sensitivity of the tender points in our participants. Although we took care in the pressures that we applied to the participants during the assessment, the predetermined force could have affected the tender point sensitivity to confound our results.
Using methods of pain threshold and pain provocation strengthened our study by including measures that could be altered by the treatment, especially because the resting pain values were so low. However, the pain provocation test may have had a therapeutic effect similar to shiatsu massage. Furthermore, by minimizing the manipulation of the tissues, it was more difficult to distinguish trigger from tender points in this otherwise healthy population. Therefore, we considered this study to be a pilot test to establish the feasibility of using a single 90-second SCS treatment in a convenience sample. Future studies should include a true control with no treatment given that the manipulation of the area in the evaluation may have influenced a treatment effect.31
Strain counterstrain is a passive positional procedure that places the body in a position of greatest comfort. Pain and dysfunction are hypothesized to be reduced by decreasing inappropriate proprioceptor activity that has created the somatic dysfunction.10 The muscle spindles are reset during the passive positioning so the aberrant signals become diminished. The treating clinician in our study was trained in the proper technique of SCS and had clinical experience in manual therapy.
The technique we used for SCS was developed by Jones and Ontario34 and other clinicians8 who have used passive position to elicit their results. Meseguer et al13 used SCS to effectively decrease tender point pain in the upper trapezius, but his technique used a sitting position with the noninvolved arm abducted while downward pressure was exerted over the upper trapezius. This technique is also described by D’Ambrogio and Roth16, but is often recommended when the tender point is caused by an elevated rib. The complexity of the treatment and the potential for confounding techniques remains a problem with all research on manual therapy. We chose the procedure in which the participant was supine, the neck was laterally flexed and rotated, with the involved arm placed in flexion and rotation, assuming that we would be able to consistently place the upper trapezius in a relaxed position. There are many positions that can be used for similar etiologies, and the choice of position and election to treat all participants similarly may have affected our results.
Future research should be directed at more accurately evaluating the theory behind SCS and should perhaps include activation measures such as electromyography to support the effects on the muscle spindle. Both the SCS and sham treatments resulted in a main effect for time, indicating there was no superior treatment effect.
Our study presents a design to evaluate the effectiveness of a single treatment both immediately and 24 hours later. Manual therapy is rarely used in isolation and its effects should be examined in conjunction with a typical therapeutic regimen. Clinically, we would use a treatment such as SCS to evoke pain relief so that rehabilitative efforts could address muscle strength and performance deficits during functional movement. Outcome data that captures the entire therapeutic process would be valuable, but unlikely to account for the variation in treatment approaches.
Pain at rest, provoked pain, and pain threshold did not significantly differ between the SCS treatment and the sham treatment. Our results showed no evidence to support the use of SCS over the sham treatment. Additional research on SCS is necessary to address the effectiveness of SCS as part of a comprehensive treatment program.
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- De Las Penas CF, Campo MS, Carnero JF, Page JCM. Manual therapies in myofascial trigger point treatment: A systematic review. Journal of Bodywork and Movement Therapies. 2005;9:27–34. doi:10.1016/j.jbmt.2003.11.001 [CrossRef]
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Means and Standard Deviations of Measurements
|RESTING PAIN||PAIN THRESHOLD||PROVOKED PAIN|
|BASELINE||POSTTREATMENT||24-HOUR POSTASSESSMENT||BASELINE||POSTTREATMENT||24-HOUR POSTASSESSMENT||BASELINE||POSTTREATMENT||24-HOUR POSTASSESSMENT|
|SCS mean (SD)||1.0 (1.3)||0.3 (0.5)||0.2 (0.4)a||3.5 (1.2)||3.7 (1.3)||3.8 (1.1)||5.1 (1.8)||4.7 (2.4)||4.1 (2.7)|
|Sham mean (SD)||1.4 (1.5)||0.8 (1.3)||0.3 (0.5)||2.6 (1.6)||3.2 (1.2)||3.5 (1.8)||5.9 (1.5)||5.8 (2.0)||5.5 (1.8)|