Pressure Pain Thresholds and Basal Electromyographic Activities Following Spinal Mechanical Manipulation

Study Overview
=================
Brief Summary
-----------------
The purpose of this study is to investigate if the application of spinal mechanical manipulation on low back region resulted in changes in pressure pain thresholds (PPT) in asymptomatic subjects and the extent of the hypoalgesia; whether it is local, regional or systemic. Simultaneously, the investigators are to further explore the phenomenon of reduced sEMG activity after spinal mechanical manipulation to better understand the immediate effects of mechanical manipulation on low back region.

Detailed Description
-----------------
Spinal manipulation (SM) is used by clinicians for the treatment of several chronic pain conditions. The effectiveness of different spinal manipulations targeted at the lumbar spine in patients with low back pain is supported by an increasing number of high-quality randomized clinical trials1and systematic reviews. Although these techniques have shown some effectiveness in clinical practice, most of clinical studies solely investigated the effects of spinal manipulation on overall reports of pain and function and the underlying mechanisms by which manipulation produce clinical effects remain largely unknown. The neurophysiologic mechanisms by which manipulation inhibits pain, however, are matters of speculation and still under investigation. Proposed hypotheses have suggested that manipulation has the potential to remove the source of mechanical pain or induce stimulus-produced analgesia. Spinal manipulation induces sufficient force to simultaneously activate both superficial and deep somatic mechanoreceptors, proprioceptors, and nociceptors. The effect of this stimulation is a strong afferent segmental barrage of spinal cord sensory neurons, capable of altering the pattern of afferent input to the central nervous system and inhibiting the central transmission of pain. Other suggested mechanisms have been the activation of the endogenous opiate system, the alteration of the chemical mediators or the effects of joint cavitation. An understanding of the mechanism by which manipulations cause a hypoalgesic response is subject to further research and is currently far from complete. A review of the literature found several studies exploring immediate changes in mechanical pain sensitivity provoked by spinal manipulative procedures. Mobilisation/manipulation to the cervical spine has been shown to provide a hypoalgesic effect as measured by pressure pain thresholds (PPTs) in patients suffering from mechanical neck pain and lateral epicondylalgia. A hypoalgesic effect has also been demonstrated following mobilization to peripheral joints in the upper and lower limbs. Mobilizations to the lumbar spine have been shown to produce an immediate and significant widespread hypoalgesic effect in asymptomatic subjects However, Perry et al. that found unilateral mobilizations on the lumbar spine respectively had side specific response. Besides analgesic effect, it has been presented spinal manipulation can reduce the increased resting muscle tone or spasm, which can be monitored by surface electromyography (sEMG). If the presence of a hypertonic muscle is functionally associated with a spinal dysfunction that is correctable by SM, it would consequently follow that the associated higher EMG level would diminish after appropriate SM. In a descriptive study DeVocht JW et al. found that manipulation induces an immediate change, usually a reduction, in resting EMG level in patients with low back pain. Herzog J reported the observation of a single but very dramatic decrease in resting EMG activity in thoracic musculature within 1 second of SM. One possible segmental mechanism could be that the manipulation may induce a reflex muscle relaxation by modifying proprioceptive group 1 and 2 afferents. However, few randomly controlled trials have directly investigated the effect of spinal mechanical manipulation on basal electromyographic activity (BEA) in asymptomatic subjects. Spinal mechanical manipulation has been widely used in clinical manual therapy. However, because mechanical thrusts usually produce no cavitations, whether mechanical techniques produce the same hypoalgesic effects and muscle relaxation as manual techniques remains untested. To further elucidate the physiologic mechanisms associated with spinal mechanical manipulation, it is essential to investigate its effects in asymptomatic individuals who do not have any active central sensitization. In fact, recent studies have supported the use of asymptomatic subjects in studies related to neurophysiological mechanisms of spinal manipulations. Further research is therefore required to clarify if there is a hypoalgesic effect or muscle relaxation in response to spinal mechanical manipulation in the lumbar region in asymptomatic subjects.

Official Title
-----------------
Changes in Pressure Pain Thresholds and Basal Electromyographic Activities Following Spinal Mechanical Manipulation in Asymptomatic Subjects

Conditions
-----------------
Pain

Intervention / Treatment
-----------------
* Other: Spinal mechanical manipulation intervention
* Other: Sham manipulation intervention


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: asymptomatic volunteers age from 18 to 60 years Exclusion Criteria: aversion to manual contact symptoms in the low back or lower extremities previous history of spine surgery receiving any manual therapy within the past 1 month before the study any contraindication to manipulation regular use of analgesic or anti-inflammatory drugs

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 60 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: experimental group<br>The experimental group receives the real spinal mechanical manipulation. | Other: Spinal mechanical manipulation intervention<br>* Subjects in experimental group are assessed through use of the Activator Methods (AM) assessment protocol. Spinal adjustment of the indicated pelvis, sacrum and lumbar spine is performed through the use of spinal mechanical manipulation. In this study leg length analysis only uses Position #1 and Position #2. Mechanical manipulation is delivered with the Activator Ⅳ Adjusting Instrument (AAI Ⅳ; Activator Methods International, Ltd, Phoenix, AZ) set in the maximal force setting 4, as it is used in routine clinical practice. The Activator Ⅳ delivers a very short duration (<5 ms) force-time impulse with a peak force magnitude of approximately 176N.<br>* Other names: Activator methods maximal setting;|
| Sham Comparator: control group<br>The control group receives the sham-manipulation procedure. | Other: Sham manipulation intervention<br>* Subjects in the control group receive a protocol identical to that described above, with the following exception: a sham mechanical thrust is delivered during the AM protocol. The sham procedure is accomplished by setting the expansion control knob on the Activator Ⅱ to the zero (off) position. The expansion control is used to adjust the spring compression and thus the amount of excursion of the instruments' stylus. In the zero position, no excursion of the stylus occurs, although the same clicking sound that the instrument produces during normal use is heard after manual activation of the mechanical trigger.<br>* Other names: Activator methods zero setting;|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Pressure pain threshold assessment | A mechanical pressure algometer (Wagner, Greenwich, CT) is used to measure PPT levels. Participants report to stop the pressure stimulation immediately when the sensation turnes from pressure to pain. The L5-S1 zygapophyseal is chosen as a landmark local to the manipulation. The L5 dermatome is chosen to measure the extent of any hypoalgesic response. The first dorsal interossei in the hand is selected to evaluate if there was a systemic response to the manipulation. | within 10 minutes immediately after manipulation | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Basal electromyographic activity | Basal electromyographic activity (BEA) of paraspinal muscles is measured using a BioGraph@ surface electromyography with Infiniti software Systems version 1.51B (Thought Technology, Montreal, Quebec). Electrodes are 2.25-in (5.72cm) triodes, disposable, and adhesive with Ag/AgCl snaps. The electrodes are placed 30mm from the spinous process of the fourth lumbar vertebra (L4) and 10mm from the spinous process of the fifth cervical vertebra (C5). The signal is selected for 10 seconds. | within 10 minutes immediately after manipulation | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Spine, Manipulation, Pain Threshold, Electromyography.