A randomized clinical trial to compare the immediate effects of seated thoracic manipulation and targeted supine thoracic manipulation on cervical spine flexion range of motion and pain

Design:

Randomized clinical trial.

Objectives:

To determine the effectiveness of seated thoracic manipulation versus targeted supine thoracic manipulation on cervical spine pain and flexion range of motion (ROM). There is evidence that thoracic spine manipulation is an effective treatment for patients with cervical spine pain. This evidence includes a variety of techniques to manipulate the thoracic spine. Although each of them is effective, no research has compared techniques to determine which produces the best outcomes.

Methods:

A total of 39 patients with cervical spine pain were randomly assigned to either a seated thoracic manipulation or targeted supine thoracic manipulation group. Pain and flexion ROM measures were taken before and after the intervention.

Results:

Pain reduction (post-treatment–pre-treatment) was significantly greater in those patients receiving the targeted supine thoracic manipulation compared to the seated thoracic manipulation (P<0·05). Although not significant, we did observe greater improvement in flexion ROM in the targeted supine thoracic manipulation group. The results of this study indicate that a targeted supine thoracic manipulation may be more effective in reducing cervical spine pain and improving cervical flexion ROM than a seated thoracic manipulation. Future studies should include a variety of patients and physical therapists (PTs) to validate our findings.     

Uneventful upper cervical manipulation in the presence of a damaged vertebral artery

OBJECTIVE: To discuss a case in which a patient with a previously injured vertebral artery underwent manipulation in the upper cervical spine without alteration of her symptom pattern. The literature concerning the relative safety of specific upper cervical manipulative techniques is reviewed. CLINICAL FEATURES: A 42-year-old woman had a 3-week history of unilateral suboccipital pain that she related to a sudden twisting of her head and neck that occurred while she was putting sheets of drywall on top of her car. Subsequent examination by a neurologist 2 weeks later was unremarkable, and a tension-type headache was diagnosed. Approximately 10 days later (3 weeks after injury), a single high-velocity upper-cervical manipulation (incorporating slight rotation and full lateral flexion) was performed with no change in her symptom pattern. Two weeks after that, the patient had development of a lateral medullary syndrome (also known as Wallenberg syndrome) after she briefly extended and rotated her upper cervical spine while painting a ceiling. INTERVENTION AND OUTCOME: The patient was treated with anticoagulant therapy, and the lateral medullary infarct healed without incident. The spinocerebellar and subtle motor symptoms also resolved, but the ipsilateral suboccipital headache and the loss of temperature sensation associated with the spinothalamic tract lesion were still present 9 months later. CONCLUSION: This case report demonstrates that vigorous manipulation of the upper cervical spine is possible without injuring an already damaged vertebral artery. It is suggested that the line of drive used during the single manipulation, almost pure lateral flexion with slight rotation, was responsible for the apparent innocuous response. Guidelines for the evaluation and management of vertebral artery dissection are reviewed. Because it is currently impossible to identify patients at risk of having a dissected vertebral artery with standard in-office examination procedures, rotational manipulation of the upper cervical spine should be abandoned by all practitioners, and schools should remove such techniques from their curriculums.     

Changes in proprioception and pain in patients with neck pain after upper thoracic manipulation

[Purpose] The purpose of this study was to conduct cervical stability training and upper thoracic manipulation for patients with chronic neck pain and then investigate the changes of cervical proprioception and pain. [Subjects and Methods] Subjects were 30 workers with mechanical neck pain, who were randomly divided into an upper thoracic manipulation group and a cervical stability training group. Upper thoracic manipulation after cervical stability training was conducted for the upper thoracic manipulation group, and only stability training was conducted for the cervical stability training group. The intervention period was six weeks, and consisted of three sessions a week, each of which lasted for 30 minutes. For proprioception measurement, an electro-goniometer was used to measure reposition sense before and after the intervention. The visual analogue scale was used to assess pain. [Results] After the intervention, the error angle was significantly smaller in flexion and right left side-bending, and pain was significantly reduced in the upper thoracic manipulation group. According to the post intervention comparison of the two groups, there were significant differences in the proprioception and pain values. [Conclusion] Conducting both cervical stability training and upper thoracic manipulation for patients with chronic neck pain was more helpful for the improvement of proprioception and pain than cervical stability training alone.     

颈脊柱推拿对减轻慢性颈痛患者肘屈肌抑制机制研究

目的:通过对16例慢性颈痛患者进行研究,测量颈痛患者行颈脊柱推拿前后功能量和主观疼痛改变情况。方法:颈脊柱推拿选定C5-7水平,用插入颤搐方法和肌电描记法评定肘屈肌在最大范围内随意收缩时二头肌激活作用。颈活动度和压痛阈用关节角度计和痛觉计进行测量。结果:治疗前,患者表现典型的二头肌抑制,颈部活动侧面受限,压痛敏感性增高。颈脊柱推拿后,二头肌抑制明显下降并伴随二头肌肌力增强,颈部活动度和压痛阈显著提高。结论:脊柱推拿术可以提高肌肉功能、颈部活动度和疼痛敏感性。     

Acute neck pain: cervical spine range of motion and position sense prior to and after joint mobilization

Despite the relatively high prevalence of cervical spine pain, the efficacy of treatment procedures is limited. In the current study, range of motion and proprioception was assessed prior to and after specific cervical spine mobilisation techniques. A 44-year-old male office worker presented with a history of cervical pain of 1 day duration. He had woken with pain, stiffness and a loss of range of motion. Examination findings indicated pain to be at C5–6 on the left side. Measurement of maximal three-dimensional cervical motion was undertaken using a Zebris system. A position matching task tested the individual's ability to actively reposition their head and neck. The treatment undertaken involved grade III down-slope mobilisations on the left side at C5–6 and C6–7 in supine lying. This technique was then progressed by placing the subject in an upright sitting position, and sustained natural apophyseal glides were performed at C6.Immediately following the treatment, the patient reported a considerable decrease in pain, less difficulty in movement and reduced stiffness. Motion analyses showed the most marked percentage improvements in range of motion after treatment were in flexion (55%), extension (35%), left rotation (56%), and left lateral flexion (22%). Ipsilateral lateral flexion with axial rotation was also notably improved following treatment. No change in proprioceptive ability was found following the treatment. The findings showed that the application of standardised specific mobilisation techniques led to substantial improvements in the range of motion and the restitution of normal coupled motion.     

Spinal manipulation does not affect pressure pain thresholds in the absence of neuromodulators: a randomized controlled trial

Background: Measurement of pressure pain threshold (PPT) is a way to determine one of the many potential treatment effects of spinal manipulative therapy.

Objective: To determine how multiple spinal manipulations administered in a single-session affected PPTs at local and distal sites in asymptomatic individuals.

Methods: Participants were randomly assigned into one of three groups: Group one (n = 18) received a lumbar manipulation followed by a cervical manipulation. Group two (n = 17) received a cervical manipulation followed by a lumbar manipulation. The control group (n = 19) received two bouts of five minutes of rest. At baseline and after each intervention or rest period, each participant’s PPTs were obtained using a handheld algometer. The PPTs were tested bilaterally over the lateral epicondyles of the humerus and over the mid-bellies of the upper trapezius, lumbar paraspinal, and the tibialis anterior muscles. This study was registered with ClinicalTrials.gov, and its Identifier is NCT02828501.

Results: Repeated-measures ANOVAs and Kruskal–Wallis tests showed no significant within- or between-group differences in PPT. Within-group effect sizes in the changes of PPT ranged from ?.48 at the left paraspinal muscles to .24 at the left lateral humeral epicondyle. Statistical power to detect significant differences at α of 0.05 was calculated to be 0.94.

Conclusions: This study suggests that in young adults who do not have current or recent symptoms of spinal pain, multiple within-session treatments of cervical and lumbar spinal manipulation fail to influence PPTs. Changes in PPT that are observed in symptomatic individuals are likely to be primarily influenced by pain-related neuromodulators rather than by an isolated, mechanical effect of spinal manipulation.     

A new 3-point bending traction method for restoring cervical lordosis and cervical manipulation: a nonrandomized clinical controlled trial

OBJECTIVE: To evaluate a new 3-point bending type of cervical traction. DESIGN: Nonrandomized controlled trial of prospective, consecutive patients compared with control subjects. Follow-up patient data were obtained at 3 and 15(1/2) months, and 8 1/10 months for controls. SETTING: Data were collected at a spine clinic in Nevada. PATIENTS: Volunteer subjects consisted of 30 patients and 24 controls. Subjects had cervicogenic pain (neck pain, headaches, arm pain, and/or numbness). Subjects were included if their Ruth Jackson radiographic stress lines measured less than 25 degrees but were excluded if they had suspected disk herniation or canal stenosis. All subjects completed the first follow-up examinations, and 25 of 30 patients completed the long-term follow-up examination. INTERVENTIONS: Spinal manipulation for pain and a new form of 3-point bending cervical traction to improve lordosis. Cervical manipulation was provided for the first 3 to 4 weeks of treatment. Traction treatment consisted of 3 to 5 sessions per week for 9 +/- 1 weeks. MAIN OUTCOMES MEASURES: Besides pain visual analog scale (VAS) ratings, pre- and posttreatment lateral cervical radiographs were analyzed. RESULTS: Control subjects reported no change in the pain VAS ratings and had no statistically significant change in segmental or global radiographic alignment. For the traction group, VAS ratings were 4.3 pretreatment and 1.6 posttreatment. Traction group radiographic measurements showed statistically significant improvements (P <.008 in all instances of statistical significance), including anterior head weight bearing (improved 6.2mm), Cobb angle at C2-7 (improved 12.1 degrees ), and angle between posterior tangents at C2-7 (improved 14.2 degrees ). For the treatment group, at 15(1/2)-month follow-up, only minimal loss of C2-7 lordosis (3.5 degrees ) was observed. CONCLUSIONS: Sagittal cervical traction with transverse load at midneck (2-way cervical traction) combined with cervical manipulation can improve cervical lordosis in 8 to 10 weeks as indicated by increases in segmental and global cervical alignment. Magnitude of lordosis at C2-7 remained stable at long-term follow-up.     

Comparison of cervical vertebral separation in the supine and seated positions using home traction units

This study was performed for the purpose of comparing the magnitude of cervical vertebral separation during cervical traction in supine and seated positions using home traction units. A repeated measures design with two within-subject factors (type of traction and time) was used. Seventeen asymptomatic volunteers received cervical traction in seated and supine position. Subjects received 5?minutes of static traction in sitting or supine using a force of 13.6?kg while in 15 degrees of neck flexion. A lateral radiograph of the cervical spine was taken before traction force was applied and after five minutes of static traction. Anterior and posterior distances between the inferior border of C2 and the superior border of C7 were measured by a radiologist. After supine traction there were significant increases (p=0.001) in posterior cervical vertebral separation compared to any changes after seated traction. There were no significant changes in anterior vertebral separation during either supine or seated traction positions (p=0.769). Supine cervical traction may be more effective for increasing posterior vertebral separation than seated cervical traction.     

颈椎荣通方联合旋提手法治疗神经根型(气滞血瘀型)颈椎病的临床疗效观察

目的:观察和评价中药颈椎荣通方联合旋提手法治疗气滞血瘀型神经根型颈椎病的临床效果。方法:选取2018年10月~2020年1月收治的符合神经根型颈椎病诊断标准,中医辨证分型为气滞血瘀型的80例患者,按就诊顺序编号,采用单盲、随机数字表法分为观察组和对照组各40例。观察组采用自拟颈椎荣通方结合旋提手法治疗,对照组仅采用旋提手法治疗,疗程均为2周。比较两组治疗2周后的临床疗效、疼痛视觉模拟评分、颈椎弓弦距。结果:经2周治疗后,观察组总有效率(92.50%)明显高于对照组(75.00%),P<0.05,差异有统计学意义;观察组疼痛视觉模拟评分明显低于对照组,P<0.05,差异有统计学意义;观察组治疗前后颈椎弓弦距差值高于对照组,P<0.05,差异有统计学意义。结论:颈椎荣通方结合旋提手法治疗神经根型(气滞血瘀型)颈椎病较单纯应用旋提手法疗效更优。     

Immediate effects of thoracic manipulation in patients with neck pain: a randomized clinical trial

Mechanical neck pain is a common occurrence in the general population resulting in a considerable economic burden. Often physical therapists will incorporate manual therapies directed at the cervical spine including joint mobilization and manipulation into the management of patients with cervical pain. Although the effectiveness of mobilization and manipulation of the cervical spine has been well documented, the small inherent risks associated with these techniques has led clinicians to frequently utilize manipulation directed at the thoracic spine in this patient population. It is hypothesized that thoracic spine manipulation may elicit similar therapeutic benefits as cervical spine manipulation while minimizing the magnitude of risk associated with the cervical technique. The purpose of this randomized clinical trial was to investigate the immediate effects of thoracic spine manipulation on perceived pain levels in patients presenting with neck pain. The results suggest that thoracic spine manipulation results in immediate analgesic effects in patients with mechanical neck pain. Further studies are needed to determine the effects of thoracic spine manipulation in patients with neck pain on long-term outcomes including function and disability.     

Effectiveness of spinal manipulative therapy in the treatment of mechanical thoracic spine pain: a pilot randomized clinical trial

BACKGROUND: To date, no substantiated studies have been performed to investigate the efficacy of spinal manipulative therapy on thoracic spinal syndromes. OBJECTIVE: To investigate the effectiveness of spinal manipulative therapy in the treatment of mechanical thoracic spine pain. STUDY DESIGN: A single-blind, randomized, comparative, controlled pilot study. SETTING: Technikon Natal Chiropractic Clinic in Durban, South Africa. PARTICIPANTS: Thirty subjects selected from the general population (from 16 to 60 years old) were randomly divided into two different treatment groups of 15 each. METHODS: The objective measurements collected were the thoracic spine ranges of motion with the BROM II goniometer and pain threshold with an algometer. The subjective information required completion of the Oswestry Back Pain Disability Index, short-form McGill Pain Questionnaire, and Numerical Pain Rating Scale-101 Questionnaire by the patient. These 3 forms and objective measurements were collected before the first and final treatment and again at the 1-month follow-up consultation. The data gathered were then statistically analyzed with use of a 95% confidence level. The nonparametric Mann-Whitney U test and the Wilcoxon signed-rank test were used to compare intergroup and intragroup data, respectively. This was conducted at the alpha =.05 level of confidence. Further assessment of the data was conducted by use of power analysis. INTERVENTIONS: The treatment group received thoracic spinal manipulation. The placebo group received nonfunctional ultrasound application only. The research project was carried out so that both groups received 6 treatments over a period of 2 to 3 weeks. A 1-month follow-up appointment was scheduled after the final treatment to assess the relative long-term benefits of the two different treatments. RESULTS: Statistically significant results (P < or = .025) were noted for the percentage of pain experienced (Numerical Pain Rating Scale) and for right and left lateral flexion during intergroup comparison after the final treatment. The final treatment results were maintained at the 1-month follow-up consultation; however, there were no further statistically significant results. It was noted that the power was weak, so the probability of committing type II error (falsely accepting the null hypothesis) for the other measurements was high. The intragroup analysis showed statistically significant improvements in the group that received spinal manipulative therapy in both subjective and objective measurements between the first to final treatment and the first treatment to the 1-month follow-up consultation. The placebo group analysis showed a statistically significant improvement in sensory pain only (subjective measurement) between the first treatment and the final treatment. CONCLUSIONS: This pilot study suggests that spinal manipulative therapy has greater benefits than placebo treatment. The sample size was small, therefore the findings of this trial study should not be considered conclusive but rather should be used as a foundation for planning future studies. In further studies a larger sample size will be necessary to identify subtle changes in measurement parameters and to add to the validity of the results.     

Movement behaviour in patients with chronic neck pain

Background and Purpose. The present study evaluated whether patients with chronic neck pain demonstrate characteristic angular movement deviations during repeated cervical spine movements. Method. Sixteen patients with chronic neck pain and a group of 18 aged‐matched healthy control subjects performed 10 repetitive maximal cervical movement cycles (flexion/extension, rotation, lateral flexion) at a self‐determined velocity. To collect the kinematic data of the cervical spine, a three‐dimensional ultrasonic movement analysis system (Zebris CMS70^©, Germany) was used. To describe the movement variability in the maximum oscillation amplitudies the intra‐subject coefficients of variation (CV %) was calculated. The maximum difference was characterized by the absolute differences between the minimum and maximum oscillation amplitudes of iterated movement cycles. Pain intensity was obtained by visual analogue scales (VAS). Results. The average pain rating of the patients with chronic neck pain indicated moderate neck pain intensity (3.7 (±0.8)). Independent Student's t‐tests revealed a significantly decreased range of movement (ROM) in the chronic neck pain group for all anatomic values (p < 0.05), except for the lateral flexion to the right. The maximum differences and variability parameters showed significantly increased values in the chronic neck pain group in all directions (p < 0.001). Conclusion. Maximal cervical ROM was significantly lower, and movement variability was significantly higher, in patients compared with healthy control subjects. The differences of cervical motion variability point towards increased movement irregularities in patients with chronic neck pain. The present study shows evidence to support the hypothesis that additional information may be gained from the analysis of movement variability. Copyright © 2007 John Wiley & Sons, Ltd.     

Comparative short-term effects of two thoracic spinal manipulation techniques in subjects with chronic mechanical neck pain: A randomized controlled trial

Spinal Manipulation (SM) has been purported to decrease pain and improve function in subjects with non-specific neck pain. Previous research has investigated which individuals with non-specific neck pain will be more likely to benefit from SM. It has not yet been proven whether or not the effectiveness of thoracic SM depends on the specific technique being used. This double-blind randomized trial has compared the short-term effects of two thoracic SM maneuvers in subjects with chronic non-specific neck pain. Sixty participants were distributed randomly into two groups. One group received the Dog technique (n = 30), with the subject in supine position, and the other group underwent the Toggle-Recoil technique (n = 30), with the participant lying prone, T4 being the targeted area in both cases. Evaluations were made of self-reported neck pain (Visual Analogue Scale); neck mobility (Cervical Range of Motion); and pressure pain threshold at the cervical and thoracic levels (C4 and T4 spinous process) and over the site described for location of tense bands of the upper trapezius muscle. Measurements were taken before intervention, immediately afterward, and 20 min later. Both maneuvers improved neck mobility and mechanosensitivity and reduced pain in the short term. No major or clinical differences were found between the groups. In the between-groups comparison slightly better results were observed in the Toggle-Recoil group only for cervical extension (p = 0.009), right lateral flexion (p = 0.004) and left rotation (p < 0.05).     

Chiropractic manipulative therapy and low-level laser therapy in the management of cervical facet dysfunction: a randomized controlled study

Purpose

The aim of this study was to determine the short-term effect of chiropractic joint manipulation therapy (CMT) and low-level laser therapy (LLLT) on pain and range of motion in the management of cervical facet dysfunction.

Methods

Sixty ambulatory women between the ages of 18 and 40 years with cervical facet joint pain of more than 30-day duration and normal neurologic examination were randomized to receive 1 of 3 treatment options: (1) CMT of the cervical spine, (2) LLLT applied to the cervical facet joints, or (3) a combination of CMT and LLLT. Each participant received 6 treatments in 3 weeks. The main outcome measures were as follows: the Numerical Pain Rating Scale, Neck Disability Index, Cervical Range of Motion Instrument, and Baseline Digital Inclinometer. Measurements were taken during weeks 1 (baseline), 2, 3, and 4.

Results

No differences existed between the 3 groups at baseline. A significant difference was seen between groups 1 (CMT) and 2 (LLLT) for cervical flexion, between groups 1 (CMT) and 3 (CMT + LLLT) for cervical flexion and rotation, and between groups 2 (LLLT) and 3 (CMT + LLLT) for pain disability in everyday life, lateral flexion, and rotation.

Conclusion

All 3 groups showed improvement in the primary and secondary outcomes. A combination of CMT and LLLT was more effective than either of the 2 on their own. Both therapies are indicated as potentially beneficial treatments for cervical facet dysfunction. Further studies are needed to explore optimal treatment procedures for CMT and LLLT and the possible mechanism of interaction between therapies.     

Isometric osteopathic manipulation influences on cervical ranges of motion and correlation with osteopathic palpatory diagnosis: A randomized trial

IntroductionIsometric manipulation is a current practice in osteopathy and treatment benefits have been reported in the literature. Such benefits could be assessed using experimental non-invasive cervical mobility measurements. The main objective was to quantitatively measure the effects of isometric manipulation on principal and compensatory cervical motions.Methods101 healthy volunteers were included in this study. 51 healthy volunteers selected randomly underwent the experimental protocol before and after isometric treatment and were compared to 50 healthy volunteers who underwent a placebo treatment. Osteopathic diagnosis was performed on each healthy volunteer before and after the treatment. The experimental protocol included measurements by a motion capture system focusing on principal range of motion and compensatory motions.ResultsIn both the isometric and the placebo sample, respectively including 51 (age: 29.2 ± 8.1, BMI: 22.2 ± 3.5) and 50 healthy volunteers (age: 27.4 ± 6.8, BMI: 22.9 ± 2.8), a pre-treatment diagnosis revealed a light cervical dysfunction in all subjects, mainly in levels C3 and C4. Altered ranges of motion thresholds (C3/C4 alterations) were identified: 113.2° for flexion, 130.0° for rotation and 90.2° for lateral flexion.After manipulations, the volunteers who underwent the isometric treatment presented a slight increase in amplitude for lateral flexion (p < 0.04), which was not found in the volunteers who underwent the placebo treatment. Compensatory motions showed differences pre and post isometric treatment without reaching significant values.ConclusionPrincipal ranges of motion were found significantly higher after osteopathic treatment when compared to the placebo treatment. Osteopathic palpatory diagnosis showed significant correlation with range of motions before treatment.     

The Effect of a New Neck Support Tying Method Using Thera-Band on Cervical ROM and Shoulder Muscle Pain after Overhead Work

[Purpose] This study proposed a new neck support tying (NST) method using Thera-Band for the prevention of neck and shoulder pain in workers doing overhead work. The purpose of this study was to investigate the effect of the new NST method using Thera-Band on cervical ROM and shoulder pain after overhead work. [Subjects] Fourteen male subjects were recruited. [Methods] This study measured the cervical ROM and pressure pain threshold (PPT) of the upper and middle trapezius (UT and MT) muscles after the control and NST groups had performed overhead work. [Results] The cervical flexion, extension, and lateral flexion angles of the NST group were significantly larger than those of the control group. The PPTs of UT and MT of the NST group were significantly higher than those of the control group [Conclusion] The NST prevented ROM reduction and pain in the cervical and shoulder regions.Key words: Neck supporter, Overhead work, Thera-Band     

Treatment of cervical radiculopathy with flexion distraction

OBJECTIVE: To discuss the nonsurgical treatment of a cervical disk herniation with flexion distraction manipulation. CLINICAL FEATURES: A case study of cervical disk syndrome with radicular symptoms is presented. Magnetic resonance imaging revealed a large C5-C6 disk herniation. Degenerative changes at the affected level were demonstrated on cervical spine plain film radiographs. INTERVENTION AND OUTCOME: The patient received treatment in the form of flexion distraction manipulation and adjunctive therapies. A complete resolution of the patient's subjective complaints was achieved. CONCLUSION: Flexion distraction has been a technique associated with musculoskeletal conditions of the lumbar spine. Flexion distraction applied to the cervical spine might be an effective therapy in the treatment of cervical disk herniations. Although further controlled studies are needed, treatment of cervical disk syndromes with flexion distraction might be a viable form of conservative care.     

Immediate effects of spinal manipulation on nitric oxide,substance P and pain perception

Previous studies have analyzed the effects of spinal manipulation on pain sensitivity by using several sensory modalities, but to our knowledge, no studies have focused on serum biomarkers involved in the nociceptive pathway after spinal manipulation. Our objectives were to determine the immediate effect of cervical and dorsal manipulation over the production of nitric oxide and substance P, and establishing their relationship with changes in pressure pain thresholds in asymptomatic subjects. In this single-blind randomized controlled trial, 30 asymptomatic subjects (16 men) were randomly distributed into 3 groups (n = 10 per group): control, cervical and dorsal manipulation groups. Blood samples were extracted to obtain serum. ELISA assay for substance P and chemiluminescence analysis for nitric oxide determination were performed. Pressure pain thresholds were measured with a pressure algometer at the C5–C6 joint, the lateral epicondyle and the tibialis anterior muscle. Outcome measures were obtained before intervention, just after intervention and 2 h after intervention. Our results indicated an increase in substance P plasma level in the cervical manipulation group (70.55%) when compared with other groups (p < 0.05). This group also showed an elevation in the pressure pain threshold at C5–C6 (26.75%) and lateral epicondyle level (21.63%) immediately after the intervention (p < 0.05). No changes in nitric oxide production were observed. In conclusion, mechanical stimulus provided by cervical manipulation increases substance P levels and pressure pain threshold but does not change nitric oxide concentrations. Part of the hypoalgesic effect of spinal manipulation may be due to the action of substance P.