THE PREVALENCE OF myofascial pain syndrome, a common

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1 1406 Immediate Effects of Various Physical Therapeutic Modalities on Cervical Myofascial Pain and Trigger-Point Sensitivity Chuen-Ru Hou, PhD, Li-Chen Tsai, MS, Kuang-Feng Cheng, MS, Kao-Chi Chung, PhD, Chang-Zern Hong, MD ABSTRACT. Hou C-R, Tsai L-C, Cheng K-F, Chung K-C, Hong C-Z. Immediate effects of various physical therapeutic modalities on cervical myofascial pain and trigger-point sensitivity. Arch Phys Med Rehabil 2002;83: Objective: To investigate the immediate effect of physical therapeutic modalities on myofascial pain in the upper trapezius muscle. Design: Randomized controlled trial. Setting: Institutional practice. Patients: One hundred nineteen subjects with palpably active myofascial trigger points (MTrPs). Intervention: Stage 1 evaluated the immediate effect of ischemic compression, including 2 treatment pressures (P1, pain threshold; P2, averaged pain threshold and tolerance) and 3 durations (T1, 30s; T2, 60s; T3, 90s). Stage 2 evaluated 6 therapeutics combinations, including groups B1 (hot pack plus active range of motion [ROM]), B2 (B1 plus ischemic compression), B3 (B2 plus transcutaneous electric nerve stimulation [TENS]), B4 (B1 plus stretch with spray), B5 (B4 plus TENS), and B6 (B1 plus interferential current and myofascial release). Main Outcome Measures: The indexes of changes in pain threshold (IThC), pain tolerance (IToC), visual analog scale (IVC), and ROM (IRC) were evaluated for treatment effect. Results: In stage 1, the IThC, IToC, IVC, and IRC were significantly improved in the groups P1T3, P2T2, and P2T3 compared with the P1T1 and P1T2 treatments (P.05). In stage 2, groups B3, B5, and B6 showed significant improvement in IThC, ItoC, and IVC compared with the B1 group; groups B4, B5, and B6 showed significant improvement in IRC compared with group B1 (P.05). Conclusions: Ischemic compression therapy provides alternative treatments using either low pressure (pain threshold) and a long duration (90s) or high pressure (the average of pain threshold and pain tolerance) and short duration (30s) for immediate pain relief and MTrP sensitivity suppression. Results suggest that therapeutic combinations such as hot pack plus active ROM and stretch with spray, hot pack plus active ROM and stretch with spray as well as TENS, and hot pack plus active ROM and interferential current as well as myofascial release technique, are most effective for easing MTrP pain and increasing cervical ROM. Key Words: Myofascial pain syndromes; Neck; Rehabilitation; Trigger points, myofascial. From the Institute of Biomedical Engineering (Hou, Tsai, Chung) and Department of Physical Medicine and Rehabilitation (Hong), National Cheng Kung University, Tainan; and Lin-Jin Shin Hospital, Kaohsiung (Cheng), Taiwan. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Chuen-Ru Hou, PhD, Institute of Biomedical Engineering, National Cheng Kung University, No. 1, Ta-Hsueh Rd, Tainan 701, Taiwan, hcr@speech114.csie.ncku.edu.tw /02/ $35.00/0 doi: /apmr by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation THE PREVALENCE OF myofascial pain syndrome, a common musculoskeletal pain disorder, has been increasing dramatically in recent years. 1-3 Clinically, persons with cervical myofascial pain syndrome have a very high recurrence rate. 4 Its symptoms that affect patients daily activities, include neck stiffness and pains and frequent headaches, dizziness, nausea, vomiting, and insomnia. 4 Myofascial pain syndrome is characterized by myofascial trigger points (MTrPs) in a palpable taut band of skeletal muscle and referred pain to a remote location. 4 Since the 1970s, the concept of MTrPs and associated research and clinical trials have improved our understanding of the pathogenesis of myofascial pain. 5 However, the clinical efficacy of treatment to alleviate pain has not been well established. Simons et al 4,6,7 have hypothesized that the pathophysiology of myofascial pain syndrome and formation of MTrPs result from injured or overstressed muscle fibers, leading to involuntary shorting and loss of oxygen and nutrient supply, with increased metabolic demand on local tissues. MTrP is a painful or sensitive spot in a palpable taut band of skeletal muscle fibers. An active trigger point is one with spontaneous pain or pain in response to movement, whereas a latent trigger point is a sensitive spot that causes pain or discomfort only in response to compression. Clinically, most myofascial pain syndrome treatments with either injection or physical therapy are targeted at MTrPs in the palpable taut band. Conventional treatments include manual therapy, electric therapy, cold and heat therapy, local anesthetic, and needle injection. 4,8-12 Stretch, massage, ischemic compression, and myofascial release techniques are frequently used in manual therapy. Williams and Elkins 13 claim that massage is the single most effective treatment for MTrPs of the hand. Thermotherapy, in the form of moist heat, has been recommended for the treatment of MTrPs because it tends to increase local circulation, to relax the underlying muscles, and to diminish the tension on MTrPs. 4 Ischemic compression changes the circulatory perfusion of skin and is especially valuable in muscles that are not suitable for stretch and spray and in muscles that are relatively thin and overlie bone, such as the infraspinatus and the sternalis. 4 Spray and stretch is among the most frequently used methods for treating MTrPs and can sometimes provide immediate pain relief. 4 The purpose of myofascial release is to move superficial tissues over the underlying structures to improve their mobility and to relieve the subcutaneous tightness of panniculosis. Since the development of the gate control theory of pain perception by Melzack and Wall in 1965, 14 transcutaneous electric nerve stimulation (TENS) has been used successfully to treat acute and chronic pain conditions The effect of TENS on pain relief may be through a peripheral mechanism or central effects that increase circulating endogenous opiates 23 or that modulate autonomic response Interferential current therapy has a suppressing effect on the sympathetic segment of the automatic

2 EFFECTS OF PHYSICAL THERAPY ON MYOFASCIAL PAIN, Hou 1407 Group Table 1: Subjects Data in Stages 1 and 2 n Sample Sizes of MTrPs Women Men Mean Age SD (y) Stage 1 P1T P1T P1T P2T P2T P2T Stage 2 B B B B B B Abbreviations: P1, pain threshold; P2, average of pain threshold and pain tolerance; T1, 30s; T2, 60s; T3, 90s; B1, hot pack plus active ROM; B2, hot pack plus active ROM and ischemic compression; B3, hot pack plus active ROM, ischemic compression, and TENS; B4, hot pack plus active ROM and stretch with spray; B5, hot pack plus active ROM, stretch with spray, and TENS; B6, hot pack plus active ROM, interferential current, and myofascial release technique. nervous system to reduce severe pain and a stimulating effect on blood circulation to improve tissue oxygen supply and to rapidly eliminate toxic metabolic products. 27 The severity of myofascial pain syndrome depends on the pain of MTrPs in taut band. Therefore, it is important to determine the exact location of MTrPs and to quantify the degree of myofascial pain objectively. Electromyography has been useful in MTrP research studies, but its clinical application requires well-trained specialists and is expensive. In recent years, pressure algometers and thermography have been developed that provide simple and objective evaluation in detecting MTrPs, in determining trigger point sensitivity, and in improving pain relief Pressure algometers include the pressure threshold meter (PThM), the pressure tolerance meter (PToM), and the tissue compliance meter. Fischer 32 used the PThM to find an increased pain threshold of MTrPs after coolant spray or trigger-point injection treatment. Jaeger and Reeves, 34 using Table 3: Means and SDs of Pain Threshold, Pain Tolerance, and VAS Ratios in Stage 1 Pressure Duration T1 (30s) T2 (60s) T3 (90s) IThC (pain threshold) P P IToC (pain tolerance) P P IVC (VAS ratio) P P the same PThM, showed a significant increase in pain threshold of MTrPs with vapocoolant spray and passive stretch treatments. The PToM measures pain tolerance in normal muscle and bone. 31 These quantitative measuring devices are all valuable tools for investigating the treatment effect of various physical therapy modalities on myofascial pain syndrome. This study investigated the immediate effect of commonly used physical therapeutic modalities on the upper trapezius muscle of patients with cervical myofascial pain syndrome. The modalities included combinations of hot pack, active range of motion (ROM), ischemic compression, TENS, stretch with spray, interferential current, and myofascial release techniques. Pain threshold, pain tolerance, visual analog scale (VAS) for pain, 35 and cervical ROM were used as the parameters on comparative evaluation for pre- and posttreatment immediately. We believed that the results would provide useful information for the clinical treatment of cervical myofascial pain. METHODS Participants and Experimental Design Patients with cervical myofascial pain were recruited from our university s department of rehabilitation medicine. A total of 119 subjects (107 women, 12 men; age range, 30 60y) with clinically active, palpable MTrPs in a single side or both sides of the upper trapezius muscle were recruited between March and October 2000 for this study. The criteria for subject selec- Table 2: Means and SDs of Pain Threshold (kg/cm 2 ), Pain Tolerance (kg/cm 2 ), and VAS (cm) in Stage 1 Pressure Duration T1 (30s) T2 (60s) T3 (90s) Pain Threshold P1 Pretreatment Posttreatment * P2 Pretreatment Posttreatment * * * Pain Tolerance P1 Pretreatment Posttreatment * P2 Pretreatment Posttreatment * * * VAS P1 Pretreatment Posttreatment * * * P2 Pretreatment Posttreatment * * * Abbreviations: P1, pressure pain threshold; P2, average of pressure pain threshold and tolerance. * Significance (P.05) based on paired t test for pre- and posttreatment.

3 1408 EFFECTS OF PHYSICAL THERAPY ON MYOFASCIAL PAIN, Hou deficits; and (5) a willingness to participate. All subjects signed informed consent forms, which were approved by the university s human investigations committee. This study was divided into 2 stages. Stage 1 included 48 women and focused on the immediate effect of ischemic compression treatments on pain reduction, trigger-point sensitivity, and improvement of cervical ROM. Two pressure loadings (P1, pain threshold; P2, averaged value of pain threshold and pain tolerance) and 3 durations (T1, 30s; T2, 60s; T3, 90s) were matched to form 6 protocols for 6 treatment groups: P1T1, P1T2, P1T3, P2T1, P2T2, and P2T3. Eight women were randomly assigned to each group. Fourteen different active MTrPs in the upper trapezius muscles of each group were studied. The determined sample size of MTrPs was based on statistical power analysis. This stage was completed to enable us to compare the immediate effect of 6 treatments and to determine objectively the most effective ischemic compression for the second stage of the study. Stage 2 investigated 6 physical therapeutic combinations and compared their immediate effects on cervical myofascial pain syndrome in the upper trapezius muscle. The 6 combinations included (1) group B1, with hot pack plus active ROM; (2) group B2, with hot pack plus active ROM and ischemic compression; (3) group B3, with hot pack plus active ROM, ischemic compression, and TENS; (4) group B4, with hot pack plus active ROM and stretch with spray; (5) group B5, with hot pack plus active ROM, stretch with spray, and TENS; and (6) group B6, with hot pack plus active ROM, interferential current, and myofascial release technique. Group B1 served as a control. The remaining 71 patients (59 women, 12 men) were randomly assigned to each group. There were 21 subjects with 35 different MTrPs in B1, 13 subjects with 22 MTrPs in B2, 9 subjects with 17 MTrPs in B3, 10 subjects with 17 MTrPs in B4, 9 subjects with 16 MTrPs in B5, and 9 subjects with 16 MTrPs in B6. The determined sample size of MTrPs and subject number in each group were based on statistical power analysis. Fig 1. The interaction effect of pressure and duration for (A) pain threshold ratio (IThC), (B) pain tolerance ratio (IToC), and (C) VAS ratio (IVC). tion included (1) no neck or shoulder surgery within the past year; (2) no clinical evidence of radiculopathy or myelopathy; (3) no history of disk disease, degenerative joint disease, fracture, or dislocation in the cervical vertebrae; (4) no cognitive Equipment and Materials In this study, instruments for treatment and evaluation included the PThM, a PToM, a TENS, b interferential current, c goniometers, VAS, hot packs, and vapocoolant (Fluori-Methane ) spray. d The PThM and PToM are handheld devices that have a force gauge fitted with rubber tip (disk surface area, 1 cm 2 ). The PThM measures the minimum applied force on muscle that induces discomfort or pain. The PToM measures the maximum force that a person can tolerate. The measuring force of the PThM is within a range from 0 to 10kg with 0.1kg resolution, whereas the PToM is within a range of 0 to 20kg with 0.2kg resolution. A hold button is used in both the PThM and PToM for the force reading. The TENS unit has 4 electrode attachments, and both the quantity and quality of stimulation Table 4: Means and SDs of IRC of 3 df in Stage 1 Group/ROM Flexion Extension Right-Side Bending Left-Side Bending Right Rotation Left Rotation P1T P1T P1T3* P2T1* P2T2* P2T3* * Significance (P.05) for multivariate ANOVA.

4 EFFECTS OF PHYSICAL THERAPY ON MYOFASCIAL PAIN, Hou 1409 are determined by 4 parameters: pulse repetition frequency, pulse width, duration, and current intensity. The interferential current device provides a 100Hz interferential current, which superimposes the 4000 and 4100Hz current waves. The VAS is a pain assessment tool with a 10cm line anchored by the expressions no pain at all at the low end and the most intense pain imaginable at the high end of the scale. Treatments Ischemic compression therapy. Before treatment, the PThM and PToM were used to determine pain threshold and pain tolerance pressures of the MTrPs in the upper trapezius muscle for subjects. The minimum applied compressed force that induced pain or discomfort in each patient was determined by placing the PThM s rubber tip directly on the MTrP. The maximum compressive force that a subject could tolerate was measured by placing the rubber tip of the PToM directly on the MTrP. In the first stage experiment, the compressive loading of each subject s pain threshold pressure was applied for 30, 60, and 90 seconds on the MTrPs of the patients in groups P1T1, P1T2, and P1T3, respectively. Then, the averaged pain threshold and pain tolerance pressures of each subject in groups P2T1, P2T2, and P2T3 were applied to the MTrP for 30, 60, and 90 seconds, respectively. In stage 2, the ischemic compression with averaged pressure of pain threshold and pain tolerance of each subject was applied for 90 seconds on the MTrPs of patients in the B2 and B3 groups. Hot pack therapy. In this superficial heat modality, a hydrocollator hot pack was placed on the subject s cervical paraspinal and upper thoracic areas (including the upper trapezius muscle with MTrPs) for 20 minutes. Active ROM. The joint of the cervical spine was voluntarily bent to the opposite side and rotated to the same side of the involved MTrP upper trapezius muscle with 5 repetitions for each treatment in the second stage. Spray with stretch. The subject sat comfortably and relaxed in a low-backed, firm-seated armchair with the fingers of each hand hooked under the chair seat. The therapist stretched the upper trapezius muscle (with the MTrP) for maximum lengthening and pressed the subject s head forward to raise the occiput. At the same time, the therapist applied the vapocoolant spray in parallel sweeps from the acromion to the mastoid area. TENS therapy. The negative electrode of the TENS unit was placed on the MTrP of the upper trapezius muscle, and the positive electrode was placed on the acromial tendon insertional site of the muscle. The current, with an asymmetrical rectangular biphasic form, was applied at a pulse repetition frequency of 100Hz and duty cycle of 250 s; the intensity was set at a level that each subject could feel but that was not strong enough to induce muscle contraction. The current was applied for 20 minutes. Interferential current therapy. Four electrodes were placed around the upper trapezius muscle with MTrP. A pair of electrodes with a current frequency of 4000Hz crossed another pair of electrodes with current frequency of 4100Hz to stimulate the target muscle. The treatment duration was 20 minutes. Myofascial release technique. The subject was supine and the therapist sat behind the subject s head with hands placed on the subject s upper shoulders to stretch the upper trapezius muscles bilaterally. The direction of stretch was downward and outward. Unilateral stretching and traction of the shoulder portion involving the upper trapezius with MTrP were then applied. Procedures Subjects were instructed separately according to the specific procedure of first and second stages. Before the experiment, each subject was informed about the conditions they might experience and possible side effects, such as discomfort. Then Fig 2. Correlation scatterplots for pretreatment in stage 1: (A) pain threshold correlated positively with pain tolerance (R.830, P<.01; y 1.20x 0.48), (B) VAS correlated negatively with pain threshold (R.250, P<.05; y.40x 6.75); and (C) VAS correlated negatively with pain tolerance (R.305, P<.01; y.33x).

5 1410 EFFECTS OF PHYSICAL THERAPY ON MYOFASCIAL PAIN, Hou age, sex, diagnosis, and history of myofascial pain syndrome symptoms were recorded. The experiment was conducted by an experienced physical therapist. For both stages, subjects were randomly assigned to an experiment group. After an active MTrP in the upper trapezius muscle was located and marked with an X, pretreatment measures of pain threshold and pain tolerance, using pressure algometers and the VAS, pain intensities of MTrPs were recorded, following the procedures by Reeves et al 33 and Jaeger and Reeves. 34 In addition, cervical ROM, including flexion and extension, right- and left-side bending, and right and left rotation in 3 df, was evaluated and recorded 3 times with repeated measures using a goniometer. ROM was a multivariate vector variable consisting of 6 parameters of flexion and extension, right- and left-side bending, and right and left rotation. In stage 1, subjects randomly received 1 of the 6 ischemic compression treatments immediately after the pretreatment measuring. Pain threshold, pain tolerance, VAS pain intensity, and ROM measures were recorded within 5 minutes after ischemic compression. The treatment outcome that showed the most improvement was selected for use in stage 2. At stage 2, all subjects received the same control treatment (B1) of hot pack for 20 minutes and active ROM exercise of the cervical joint immediately after the pretreatment measuring. The ischemic compression treatment from stage 1, the TENS procedure by Graff-Radford et al, 36 the stretch and spray treatment described by Simons et al, 4 and the interferential current treatment with 100Hz interfering wave was continued for 20 minutes. Within 5 minutes of completing treatment, pain threshold, pain tolerance, VAS pain intensity, and ROM measure were recorded. Statistical Methods and Analysis To analyze the immediate effect of treatments, data were normalized to minimize parameter variations. The parameter ratio of post- to pretreatment was used as an evaluation index. The 4 clinical indexes included pain threshold change (IThC), pain tolerance change (IToC), VAS change (IVC), and ROM change (IRC). When the indexes IThC, IToC, and IRC are greater than 1 and IVC is less than 1, the treatment effect is considered positive; otherwise, a negative effect is assumed. In stage 1, a paired t test was used initially to compare pain threshold, pain tolerance, and VAS values for pre- and posttreatment of each group. Then a 2 3 two-way analysis of variance (ANOVA) was used to analyze the effect of the compression pressure factor (P), the time duration factor (T), and the P T interaction for pain threshold, pain tolerance, and VAS values on the 6 treatment groups. Flexion and extension, right- and left-side bending, and right and left rotation of the cervical joint of each subject formed an ROM vector. Comparisons of the ROM vector among the 6 groups were analyzed by using the Hotelling T 2 test of multivariate data. The Pearson correlation method was used to analyze the correlation among the pain threshold, pain tolerance, and VAS values for the 3 indexes of MTrP sensitivity. In stage 2, a paired t test was used initially to compare pain threshold, pain tolerance, and VAS values for pre- and posttreatment of each group. Then a 1-way ANOVA was used to analyze the immediate effect for 6 treatments. The ROM of the cervical joint was analyzed by using the same method as in the first stage. Significance was set equal to.05. RESULTS Fig 3. Correlation scatterplots for posttreatment in stage 1: (A) pain threshold correlated positively with pain tolerance (R.802, P<.01; y 1.04x 0.96); (B) VAS correlated negatively with pain threshold (R.314, P<.01; y.38x 5.39); and (C) VAS is negatively correlated with pain tolerance (R.280, P<.01; y.29x 5.35). Stage 1: Immediate Effect of Ischemic Compression With Various Pressures and Durations The data for subjects in the 6 ischemic compression groups (stage 1) are listed in table 1. The sample size of 14 MTrPs for

6 EFFECTS OF PHYSICAL THERAPY ON MYOFASCIAL PAIN, Hou 1411 each group was determined statistically by power analysis with type I error at equal to.05 and type II error at equal to 0.2 (power 0.8). Table 2 shows the means and standard deviations (SDs) of pain threshold, pain tolerance, and VAS for pre- and posttreatment. The results of the paired t tests show that the pain threshold and tolerance values of MTrPs were significantly increased after the treatment in the P1T3, P2T1, P2T2, and P2T3 groups (P.05), and the VAS value was significantly decreased after the treatment for all 6 groups (P.05). With the normalized values shown in table 3, the results of 2-way ANOVA show that both the pressure and time duration factors were significant (P.05). The P2 treatment with averaged pain threshold and tolerance pressures showed significantly higher IThC and IToC compared with the P1 treatment with pain threshold pressure (P.05). The IVC that resulted from P2 treatment was significantly lower than the change from P1 treatment (P.05). Multiple comparisons with the Tukey honestly significant difference (HSD) test show that the pain threshold and tolerance of MTrPs were significantly increased after 90 seconds of ischemic compression compared with the 60-second and 30-second treatments (P.05). The change in VAS after the 90-second treatment was significantly less than that after the 30-second treatment (P.05); that is, pain intensity after the 90-second ischemic compression treatment improved in comparison with that after the 30-second treatment. The interaction of pressure loading and time duration treatment was significant in the IThC, IToC, and IVC (P.05), as shown in figure 1 and table 3. The results show increasing IThC and IToC values, in order, from the P1T1, P1T2, P2T1, P2T2, P1T3, and to P2T3 treatment groups. Also, a decreasing IVC value was shown, in order, from P1T1, P1T2, P2T1, P1T3, P2T3, and to P2T2 treatment group. The statistical analysis of IThC, IToC, and IVC values showed that the P2T3, P2T2, and P1T3 groups had improved significantly compared with P1T1 and P1T2 treatments (P.05), but there was no significant difference among the P2T3, P2T2, and P1T3 groups. The means and SDs of the IRC for the cervical ROM ratio are shown in table 4. The results of multivariate ANOVA indicate that the IRC of cervical ROM in the P1T3, P2T1, P2T2, and P2T3 groups had significantly improved (P.05), as compared with the P1T1 and P1T2 groups, but there was no significant difference among the P1T3, P2T1, P2T2, and P2T3 groups. Figure 2 shows the relation pretreatment between pain threshold, pain tolerance, and VAS values as determined by the Pearson correlation analysis for all subjects. The relation between pain threshold, pain tolerance, and VAS values for posttreatment is shown in figure 3. For both pre- and posttreatment, the relationships show that pain threshold correlated positively with pain tolerance and that VAS correlated negatively with pain threshold and pain tolerance. Based on the results of this first-stage experiment, the ischemic compression with averaged pain threshold and pain tolerance pressures for 90-second duration treatment (P2T3 treatment) was selected for the second stage. Stage 2: Immediate Effect of 6 Physical Therapeutic Combinations The means and SDs of pain threshold, pain tolerance, and VAS for pre- and posttreatment in stage 2 are shown in table 5. The results of the paired t tests on treatment effects show that for all 6 treatment groups, pain threshold and tolerance increased significantly (P.05) and the VAS value decreased significantly (P.05) immediately after the treatment. The normalized data indicate increasing IThC and IToC values, in order, from groups B1, B2, B4, B3, B5, and to B6 (table 6). Also, a decreasing IVC value was shown, in order, from groups B1, B2, B4, B3, B5, and to B6. The results of 1-way ANOVA indicate that the IThC, IToC, and IVC were significant in the 6 treatment groups (P.05). Multiple comparisons with the Tukey HSD test show that the IThC of groups B3, B5, and B6 were significantly higher than that of the B1 control group (P.05), and the IThC of the B6 group was significantly higher than that of the B2 group (P.05) (fig 4). However, the IThC was not significant among the B2, B3, B4, and B5 groups. Figure 5 shows that the IToC of groups B3, B5, and B6 were significantly higher than the B1 control group (P.05), and the IToC of B5 and B6 were significantly higher than that of B2 (P.05), but there was no significant differences among the B2, B3, and B4 groups (P.05). Figure 6 shows that the IVC of groups B2, B3, B4, B5, and B6 were significantly lower than that of the B1 control group (P.05), and the IVC of the B3, B5, and B6 groups were significantly lower than that of the B2 group (P.05). The IVC of B6 was significantly lower than that of B4 (P.05), but there was no significant difference among B3, B5, and B6 (P.05). The means and SDs for cervical ROM change ratios are shown in table 7 for the 6 groups. The results of multivariate analysis on immediate effect indicate that the cervical ROM change in the 6 groups was significant (P.05). The IRC of groups B4, B5, and B6 improved significantly in comparison with the B1 control (P.05), but there were no significant differences among groups B2, B3, B4, B5, and B6. DISCUSSION Copper et al 37 and Fricton et al 38 have proposed that the incidence of MTrPs appears to be higher in women than in men, and that, among all age groups, patients 30 to 40 years old appear to have the highest prevalence of trigger points. Of our 119 subjects (age range, 30 60y), 107 were women, which Table 5: Means and SDs of Pain Threshold (kg/cm 2 ), Pain Tolerance (kg/cm 2 ), and VAS (cm) in Stage 2 Value/Group B1 B2 B3 B4 B5 B6 Pain threshold Pretreatment Posttreatment * * * * * * Pain tolerance Pretreatment Posttreatment * * * * * * VAS Pretreatment Posttreatment * * * * * * * Significance (P.05) based on paired t test for pre- and posttreatment.

7 1412 EFFECTS OF PHYSICAL THERAPY ON MYOFASCIAL PAIN, Hou Table 6: Means and SDs of IThC, IToC, and IVC for 6 Groups in Stage 2 Index/Group B1 B2 B3 B4 B5 B6 IThC IToC IVC indicates that the incidence of MTrPs is higher in women than in men. Patients with MTrPs in the upper trapezius muscle usually complain of neck pain, headache, muscle stiffness, restricted ROM of the cervical joint, dizziness, sweating, nausea, vomiting, and insomnia. The upper trapezius myofascial pain is frequently caused by poor posture and body position, acute trauma, muscle stress, and psychologic stress. Our results show that the PThM and PToM are not only useful in quantitatively determining the sensitivity of MTrPs (the degree of pain) but are also useful in prescribing ischemic compression therapy for immediate relief of myofascial pain. Fischer 32 reported that the average value of pain threshold SD on women s normal upper trapezius muscles was kg/cm 2. In our study, the average value of pain threshold for all subjects before treatments was kg/cm 2, and the average value after the treatments was kg/ cm 2. The results correlate closely with those reported by Fischer. In addition, all subjects in this study had an average pain tolerance pressure of kg/cm 2 before treatment and kg/cm 2 after treatment. The Pearson correlation analysis showed that the VAS, pain threshold pressure, and pain tolerance pressure correlated highly. The findings indicate that these 3 indexes are consistent in clinical assessment of the MTrP sensitivity and are useful in assessing the therapeutic effectiveness on pain relief. Pain relief from ischemic compression treatment may result from reactive hyperemia in the MTrP region, 4 counter-irritant effects, 39 or a spinal reflex mechanism for the relief of muscle spasm. 39 The pressure that is applied to the MTrP of taut band should be within a tolerable pain level for each patient to avoid causing excessive pain and autonomic responses with involuntary muscle tensing. The treatment may not be effective if insufficient pressure is applied. Therefore, an appropriate pressure prescription is important to ensure the clinical efficacy of ischemic compression therapy. In this study, the effects of 4 treatments (groups P1T3, P2T1, P2T2, P2T3) showed more than 15% (range, 16% 23%) improvement in pain threshold, 20% (range, 21% 29%) improvement in pain tolerance for MTrP sensitivity, and 30% (range, 30% 38%) reduction in VAS for pain relief. These findings imply that the applied pressure, ranging from a low value of pain threshold to a high value of average pain threshold and pain tolerance, can provide immediate pain relief and is clinically acceptable to patients. The average pressure of pain threshold and tolerance needs only a 30-second treatment to provide pain relief; however, the low pressure at pain threshold level requires 90 seconds of ischemic compression to obtain immediate pain relief. In stage 2 of our study, all 6 physical therapeutic treatments on the upper trapezius muscle resulted in an immediate suppression of MTrP sensitivity, with significantly increased pain threshold and pain tolerance, immediate pain relief with significant reduction in VAS value, and improvement in the cervical ROM. For a comparative evaluation of the immediate effects of the 6 treatments, the hot pack and active ROM treatment (group B1) served as the control. Pain relief from thermotherapy may result from relief of muscle spasm as a consequence of reduced activity of secondary (group II) afferent fibers and increased activity of primary (group Ia) afferent fibers, 40 from a reduction of painful inflammatory reactions as a consequence of increased blood flow, 4 or from the counterirritant effects of a remote reflex phenomenon or an endorphine-related mechanism. 39 The effect of active ROM exercise involves moving the joints into various positions and gently stretching the muscle to maintain the freedom of joint movement. 4 Simons et al 4 proposed that ischemic compression treatment was preferable after a hot pack and active ROM. Our study results show that there was a 33% improvement in the VAS reduction of group B2, compared with a 16% improvement in the VAS reduction of the B1 control group. These findings suggest that ischemic compression after a hot pack and active ROM is more effective in pain relief than just the hot pack and active ROM treatment. The stretch with spray added to a hot pack and active ROM treatment (group B4), resulted in a 36% improvement in the VAS reduction and in increased cervical ROM (range, 15% left rotation to 31% right-side bending improvement). Pain relief and increased ROM from spray with stretch may result from the therapeutic effect of cold spray and Fig 4. Means and SDs of pain threshold ratio (IThC) for the 6 treatment groups in second stage. * P<.05 (significance for multiple comparison with the Tukey HSD test). Fig 5. Means and SDs of pain tolerance ratio (IToC) for the 6 treatment groups in second stage. * P<.05 (significance for multiple comparison with the Tukey HSD test).

8 EFFECTS OF PHYSICAL THERAPY ON MYOFASCIAL PAIN, Hou 1413 Fig 6. Means and SDs of VAS ratio (IVC) for the 6 treatment groups in second stage. * P<.05 (significance for multiple comparison with the Tukey HSD test). release of taut bands by stretching. 4,6 Simons 6 proposed that release of taut bands is essential to break the cycle that induces the ischemic contractions in the taut band that perpetuate myofascial pain syndrome. Recent studies on referred pain and local twitch response support the concept that the MTrP mechanism is closely related to spinal cord integration. When the input from nociceptors in an original receptive field persists, central sensitization in the spinal cord may develop and the receptive field corresponding to the original dorsal horn neuron may be expanded. Through this mechanism, new MTrPs, or satellite MTrPs, may develop in the referred zone of the original MTrP. For a long-standing untreated active MTrP, the irritation from the peripheral nociceptors may be persistent, and the receptive field may expand progressively. Finally, spontaneous pain may spread to many distant regions through the mechanism of central sensitization in the spinal cord. With low-intensity current stimulation of TENS, the low-threshold large afferent fibers can be stimulated selectively, which can suppress the pain impulses from small nociceptive fibers through the gate control mechanism. 14 In 1989, Graff-Radford et al 36 reported in a comparative study of 4 modes on TENS treatment and a nonstimulated control, that high-intensity TENS was effective in treating myofascial pain without alteration of local MTrP sensitivity. They suggested that TENS alone might be insufficient for the long-term treatment of myofascial pain because MTrP sensitivity appeared to remain unaltered. The pain-reducing properties of TENS coupled with stretching would produce the desired effect of reducing pain and MTrP sensitivity. 36 Our study results indicate that the additional TENS in groups B3 and B4 provided more improvement in the pain relief and MTrP sensitivity but no favorable, significant effect on cervical ROM. These findings show that pain relief and MTrP sensitivity can be further improved by TENS coupled with ischemic compression or stretch with spray treatments. Although TENS therapy alone is not a treating modality on MTrPs, it can be used as a secondary technique when combined with other therapies for cervical myofascial pain. 4,47 The combined effect of interferential current and myofascial release therapies results in more pain relief, suppression of MTrP sensitivity, and an increase in cervical ROM. The mechanism of interferential current therapy may be because of the effects of the directly applied electrical current with stronger intensity on the involved muscle to enhance muscle circulation, to reduce muscle spasm, to eliminate muscle pain, and to increase muscle strength. 48 Pain relief from the myofascial release technique may result from breaking the limitation of muscle or connective tissue around the joint, from stimulating the mechanoreceptor, from increasing the blood flow and neuron conductance, or from local or systemic relaxation. 49 Myofascial release is a highly interactive stretching technique that requires feedback from the patient to determine the direction, force, and duration of the stretch and to facilitate maximum relaxation of the tense tissues. This technique recognizes that a muscle cannot be isolated from the other structures of the body so all muscle stretching is actually the stretching of myofascial units. CONCLUSIONS Ischemic compression therapy with quantified pressure and duration provides alterative treatments by using either the pressure of pain threshold with a long duration of 90 seconds or the pressure of the average of pain threshold and pain tolerance with a duration of 30 seconds. It provides immediate pain relief and reduces the MTrP sensitivity of the cervical myofascial pain. Immediate relief from cervical myofascial pain can be obtained in 6 therapeutic modalities. Hot pack plus active ROM, ischemic compression, and TENS therapies provide major pain relief. TENS coupled with ischemic compression therapy is more effective in pain relief than hot pack with active ROM therapy. Significant further improvement in cervical ROM can be provided by additional stretch with spray or interferential current with myofascial release therapies. Based on our findings, we suggest that the therapeutic combinations for further reduction in MTrP pain and increased cervical ROM can be used to treat upper trapezius myofascial pain. The combinations include hot pack plus active ROM and stretch with spray (group B4), hot pack plus active ROM and stretch with spray as well as TENS (group B5), and hot pack plus active ROM and interferential current as well as myofascial release technique (group B6). Alternatively, hot pack plus active ROM and ischemic compression (group B2) and hot pack plus active ROM and ischemic compression as well as TENS (group B3) combined with stretch and spray, myofascial release, or interferential current therapies are also effective. However, pain reduction, improvement of MTrP sensitivity, and increase in Group/ROM Flexion Extension Table 7: Means and SDs of IRC of 3 df in Stage 2 Right-Side Bending Left-Side Bending Right Rotation Left Rotation B B B B4* B5* B6* * Significance (P.05) for multivariate ANOVA.

9 1414 EFFECTS OF PHYSICAL THERAPY ON MYOFASCIAL PAIN, Hou ROM after each treatment may not be maintained long term. Further study is required to determine the long-term effect of various physical medicine modalities and the cumulative effects of subsequent repeated therapies. References 1. Fishbain DA, Goldberg M, Meagher BR, Steele R, Rosomoff H. Male and female chronic pain patients categorized by DSM-III psychiatric diagnostic criteria. Pain 1986;26: Fricton JR. Myofascial pain syndrome: characteristics and epidemiology. In: Fricton JR, Awad EA, editors. Myofascial pain and fibromyalgia: advances in pain research and therapy. Vol 17. New York: Raven Pr; p Skootsky SA, Jaeger B, Oye RK. Prevalence of myofascial pain in general internal medicine practice. West J Med 1989;151: Simons DG, Travell JG, Simons LS. Travell & Simons myofascial pain and dysfunction: the trigger point manual, volume 1. Upper half of body. Baltimore: Williams & Wilkins; Hong CZ, Simons DG. Pathophysiologic and electrophysiologic mechanisms of myofascial trigger points. Arch Phys Med Rehabil 1998;79: Simons DG. Myofascial pain syndrome due to trigger points. In: Goodgold J, editor. Rehabilitation medicine. St Louis: Mosby; p Simons DG. Referred phenomena of myofascial trigger points. In: Vecchiet L, Albe-Fessard D, Lindblom U, editors. Pain research and clinical management, new trends in referred pain and hyperalgesia. New York: Elsevier, p Gerwin RD. The management of myofascial pain syndrome. J Musculoskel Pain 1993;1(3/4): Melzack R. The clinical assessment of myofascial pain syndrome. In: Handbook of pain assessment. New York: Guilford Pr; p Fricton JR. Myofascial pain syndrome. Neurol Clin North Am 1989;7: James CP. Transcutaneous electrical nerve stimulation and myoneural injection therapy for management of chronic myofascial pain. Dent Clin North Am 1987;31: Rachlin ES. Trigger point management. St. Louis: Mosby; Williams HL, Elkins EC. Myalgia of the head. Arch Phys Ther 1942;23: Melzack R, Wall PD. Pain mechanism: new theory. Science 1965;150: Hansson P, Ekblom A. Transcutaneous electrical nerve stimulation (TENS) as compared to placebo TENS for the relief of acute oro-facial pain. Pain 1983;15: Hay KM. Control of head pain in migraine using transcutaneous electrical nerve stimulation. Practitioner 1982;226: Lapeer GL. High-intensity transcutaneous nerve stimulation at the Hoku acupuncture point for relief of muscular headache pain. Literature review and clinical trial. Cranio 1986;4: Melzack R. Prolonged relief of pain by brief, intense transcutaneous somatic stimulation. Pain 1975;1: Thorsteinsson G, Stonnington HH, Stillwell GK, Elvebeck LR. Transcutaneous electrical stimulation: a double blind trial of its efficacy for pain. Arch Phys Med Rehabil 1977;58: Dixon HH, O Hara M, Peterson RD. Fatigue contracture of skeletal muscle. Northwest Med 1967;66: Dubner R. Neurophysiology of pain. Dent Clin North Am 1978; 22: Wall PD, Sweet WH. Temporary abolition of pain in man. Science 1967;155: Pomeranz BH, Chiu D. Naloxone blockade of acupuncture analgesia: endorphin implicated. Life Sci 1976;19: Abram SE, Asiddao CB, Reynolds AC. Increased skin temperature during TENS. Anesth Analg 1980;59: Kaada B, Eilsen O. In search of mediators of skin vasodilatation induced by TENS: serotonin implicated. Gen Pharmacol 1983;14: Owens S, Atkinson R, Lees DE. Thermographic evidence of reduced sympathetic tone with TENS. Anesthesiology 1979;50: Nikolova L. Treatment with interference current. New York: Churchill Livingstone; Fisher AA. Documentation of myofascial trigger points. Arch Phys Med Rehabil 1988;69: Delaney GA, McKee AC. Inter- and intra-rater reliability of the pressure threshold meter in measurement of myofascial trigger sensitivity. Am J Phys Med Rehabil 1993;72: Bendtsen L, Jensen R, Jensen NK, Olesen J. Muscle palpation with controlled finger pressure: new equipment for the study of tender myofascial tissues. Pain 1994;59: Fischer AA. Pressure tolerance over muscle and bone in normal subjects. Arch Phys Med Rehabil 1986;67: Fischer AA. Pressure algometry over normal muscles. Standard values, validity and reproducibility of pressure threshold. Pain 1987;30: Reeves JL, Jaeger B, Graff-Radford SB. Reliability of pressure algometer as a measure of myofascial trigger points sensitivity. Pain 1986;24: Jaeger B, Reeves JL. Quantification of changes in myofascial trigger point sensitivity with pressure algometer following passive stretch. Pain 1986;27: McGrath PF, Unruh AM. Measurement and assessment of paediatric pain. In: Wall PD, Melzack R, editors. Textbook of pain. New York: Churchill Livingstone; 1994; p Graff-Radford SB, Reeves JL, Baker RL, Chiu D. Effects of transcutaneous electrical nerve stimulation on myofascial pain and trigger point sensitivity. Pain 1989;51: Copper BC, Alleva M, Copper DL, Lucente FE. Prevalence of myofascial pain dysfunction: analysis of 476 patients. Laryngoscope 1986;96: Fricton JR, Kroening R, Haley D, Siegert R. Myofascial pain syndrome of the head and neck: a review of the clinical characteristics of 164 patients. Oral Surg Oral Med Oral Pathol 1985; 60: Patrick DW, Melzack R. Textbook of pain. New York: Churchill Livingstone; p Mense S. Effects of temperature on the discharges of muscle spindles and tendon organ. Pflugers Arch 1978;374: Bendtsen L, Jensen R, Olesen J. Qualitative altered nociception in chronic myofascial pain. Pain 1996;65: Hong CZ. Persistence of local twitch response with loss of conduction to and from the spinal cord. Arch Phys Med Rehabil 1994;75: Hong CZ, Torigoe Y. Electrophysiologic characteristics of localized twitch responses in responsive bands of rabbit skeletal muscle fibers. J Musculoskel Pain 1994;2(2): Hong CZ, Torigoe Y, Yu J. The localized twitch responses in responsive bands of rabbit skeletal muscle fibers are related to the reflexes at spinal cord level. J Musculoskel Pain 1995;3(1): Hoheisel U, Mense S, Simons DG, Yu X-M. Appearance of new receptive fields in rat dorsal horn neurons following noxious stimulation of skeletal muscle: a model for referral of muscle pain? Neurosci Lett 1993;153: Hong CZ, Simons DG. Pathophysiologic and electrophysiologic mechanisms of myofascial trigger points. Arch Phys Med Rehabil 1998;79: Han SC, Harrison P. Myofascial pain syndrome and trigger-point management. Reg Anesth 1997;22(1): Hsueh TC, Cheng PT, Kuan TS, Hong CZ. The immediate effectiveness of electrical nerve stimulation on myofascial trigger points. Am J Phys Med Rehabil 1997;76: Manheim CJ, Lavett DK. The myofascial release manual. Thorofare (NJ): Slack; Suppliers a. Pain Diagnostics & Treatment Inc, 233 E Shore Rd, Ste 108, Great Neck, NY b. Staodynamics Inc, 1225 Flordia Ave, Box 1379, Longmont, CO c. Celcom Inc, 2213, Tokoji-Mochi, Hakata-Ku, Fukuoka 816, Japan. d. Gebauer Co, 9410 Saint Catherine Ave, Cleveland, OH