Elsevier

Manual Therapy

Volume 13, Issue 6, December 2008, Pages 492-499
Manual Therapy

Original article
An investigation into the effects of a unilaterally applied lumbar mobilisation technique on peripheral sympathetic nervous system activity in the lower limbs

https://doi.org/10.1016/j.math.2007.05.015Get rights and content

Abstract

Physiotherapeutic management of lumbar disorders often utilises specific segmental joint mobilisation techniques; however, there is only limited evidence of any neurophysiological effects and much of this has focused on the cervical spine and upper limbs. This study aims to extend the knowledge base underpinning the use of a unilaterally applied lumbar spinal mobilisation technique by exploring its effects on the peripheral sympathetic nervous system (SNS) of the lower limbs.

Using a double blind, placebo controlled, independent groups study design and based upon power calculations, 45 normal naïve healthy males were randomly assigned to one of three experimental groups (control, placebo or treatment; a unilaterally applied postero-anterior mobilisation to the left L4/5 zygopophyseal joint). SNS activity was determined by recording skin conductance (SC) obtained from lower limb electrodes connected to a BioPac unit. Validation of the placebo technique was performed by post-intervention questionnaire. Results indicated that there was a significant change in SC from baseline levels (13.5%) that was specific to the side treated for the treatment group during the intervention period (compared to placebo and control conditions).

This study provides preliminary evidence that a unilaterally applied postero-anterior mobilisation technique performed, at a rate of 2 Hz, to the left L4/5 lumbar zygopophyseal joint results in side-specific peripheral SNS changes in the lower limbs.

Introduction

Lumbar spine disorders reportedly affect around 17.3 million people in the United Kingdom at an annual cost of £1bn to the NHS and £565m to private healthcare providers (Maniadakis and Gray, 2000).

Since the publication of the recommendations of the Clinical Standards Advisory Group (CSAG, 1994), the Royal College of General Practitioners (RCGP, 1998), the UKBEAM trial (UKBEAM Trial Team, 2004) and the Clinical Guidelines for the management of Persistent LBP (CSP, 2006), the use of spinal manipulative therapy (SMT) techniques for patients with lumbar symptoms has received support as a management strategy with 58.9% of UK therapists (Foster et al., 1999) and 83.7% of North American therapists (Li and Bombardier, 2001; Poitras et al., 2005) utilising SMT as a preferred treatment for patients with low back pain (LBP).

The available evidence regarding any neurophysiological or analgesic effects that occur as a result of treatment is not always clear (Assendelft et al., 1995). Although, the last two decades have seen the emergence of conceptual models supporting the use of SMT in the management of segmental pain and joint dysfunction (Zusman, 1986, Zusman, 2004; Wright, 1995). Hypothetical mechanisms of action of SMT include: direct physiological effects on articular and peri-articular structures (Wyke and Polacek, 1975), neurophysiological mechanisms at both spinal and supraspinal levels (Wright, 1995, Wright, 1999; Solly, 2004), endocrine/hormonal effects and a non-specific placebo effect (Zusman, 1986, Zusman, 2004; Katavich, 1998).

The dilemma facing the clinician, in determining the physiological and therapeutic effects of SMT interventions on patients, is the difficulty in accurately and quantitatively measuring the proposed effects on the key target tissue. Several researchers (Petersen et al., 1993; Vicenzino et al., 1994, Vicenzino et al., 1996; Wright and Vicenzino, 1995; Chiu and Wright, 1996; Sterling et al., 2001) have explored the neurophysiological basis of specific SMT techniques in the cervical spine and upper limbs, utilising the sympathetic nervous system (SNS) as a measure of neurophysiological response. Specific SNS changes have been reported following SMT, namely; sudomotor function (Petersen et al., 1993; Slater et al., 1994; Vicenzino et al., 1994; Wright and Vicenzino, 1995; Chiu and Wright, 1996; Sterling et al., 2001); cutaneous vasomotor changes (Petersen et al., 1993) and cardiac and respiratory functions (McGuiness et al., 1997; Vicenzino et al., 1998a). Chiu and Wright (1996) compared the effects of two different frequencies/speeds of oscillation (0.5 and 2 Hz) of a cervical spine joint mobilisation technique, and observed significant SNS responses with the 2 Hz technique. This work supported that of McGuiness et al. (1997) who investigated the effects of mobilisation techniques on the magnitude of the SNS response, revealing that an oscillatory technique produced the greatest effect. This is corroborated, in part, by the findings of Moulson and Watson (2006) who applied a non-oscillatory cervical sustained natural apophyseal glide (SNAG). Despite having a sympathoexcitatory response, the magnitude of this response was not significantly greater than the placebo condition within the treatment period suggesting that the oscillatory component of the technique is an important factor in changes to SNS activity (Kenney et al., 1991; Gebber et al., 1999).

Neurophysiological (SNS) effects following SMT have revealed that in humans SMT produces an immediate hypoalgesic and sympathoexcitatory effect on both asymptomatic and symptomatic subjects that are specific to mechanical nociception as opposed to thermal nociception and sympathoinhibition (Vicenzino et al., 1995, Vicenzino et al., 1996, Vicenzino et al., 1998b; Sterling et al., 2001). These findings have led to the concept that SMT may exert its initial effects by activating descending pain inhibitory systems (DPIS) from the peri-acqueductal gray (PAG) region of the brain and, depending on whether the response is excitatory or inhibitory could indicate whether or not it is a dorsal PAG or a ventral PAG response (Wright, 1995; Wright and Vicenzino, 1995). Kenney et al. (1991) have suggested the possibility of selective and functionally complementary coupling of different post-ganglionic sympathetic nerves and, specifically, the presence of an ipsilateral preference towards observed SNS discharge. So far, these findings have not yet been applied to physiotherapy research into SMT and the lumbar spine. Indeed, studies supporting this conceptual framework have been conducted on the cervical spine (Petersen et al., 1993; Slater et al., 1994; Vicenzino et al., 1995, Vicenzino et al., 1996, Vicenzino et al., 1998b; Wright and Vicenzino, 1995; Chiu and Wright, 1996; Sterling et al., 2001; Moulson and Watson, 2006) and upper limbs (Vicenzino et al., 1994; Simon et al., 1997).

This study aimed to explore the hypothesis that a specific mechanical mid-to-end range mobilisation technique, applied to the left Lumbar 4/5 ZP joint at a rate of 2 Hz, would result in a significant change from baseline in peripheral SNS activity (as measured by skin conductance—SC) that would be greatest in the ipsilateral leg during the intervention period compared to the contra-lateral limb, the placebo and the control conditions.

Section snippets

Subjects

The study recruited a convenience sample of 45 healthy, physiotherapeutically naïve, asymptomatic, non-smoking male volunteers (aged 18–25 years, mean 21.5 years, S.D.=1.85). All volunteers were further assessed for their suitability using inclusion and exclusion criteria as described in other studies (Vicenzino et al., 1994). Subjects were randomly assigned to one of the three subject groups using the third party, concealed randomisation method (Schulz et al., 1995). An all-male group was

Instrumentation and measurement

Physiological recording of SC was measured by a Biopac GSR100B Electro-dermal Activity Amplifier (MP30; Biopac Systems Inc., Santa Barbara, CA), employing a constant voltage technique and sampling the absolute, direct current SC at the rate of 20 samples per second.

Analysis of the SC data obtained involved calculation of the “Integral Measurement” for baseline, intervention and final rest periods. These were normalised to the time period of each experimental phase. Intervention period and final

Data analysis

With independent, matched-group designs, it is important to establish homogeneity of the subjects otherwise it is difficult to determine the influence that individuals may have on the final analysis (Sim and Wright, 2002).

Statistical analysis of the data was designed to test the three elements of the hypothesis: (1) that the SMT treatment would result in a PC in SC values from baseline that were greater than those of the placebo and control conditions; (2) that any PC observed would be greatest

Laboratory conditions

Room temperature was recorded at the beginning and end of each subject's experimental session as per published guidelines (Uematsu et al., 1988) with relative constancy within each session demonstrated (mean 24.9 °C, SD 0.275, range 24.4–25.5 °C) with a maximum within subject experimental room temperature variation being no more than 0.3 °C (mean 0.2 °C, SD 0.1 °C, range 0.0–0.3 °C).

Homogeneity of the matched groups

All 45 subjects completed the study (15 per group). Statistical analysis of subject variance (Levene's Test of

Discussion

The findings of this study demonstrated that a unilaterally applied antero-posterior accessory mobilisation technique administered at a rate of 2 Hz to the left side of the L4–5 segment resulted in statistically significant side-specific changes in peripheral SNS activity during the intervention period, and that this response was greater than those of the contra-lateral limb, and of both the placebo and control conditions.

To the authors’ knowledge, no previous studies have investigated whether

References (57)

  • M. Sterling et al.

    Cervical mobilisation: concurrent effects on pain, sympathetic nervous system activity and motor activity

    Manual Therapy

    (2001)
  • B. Vicenzino et al.

    The initial effects of a cervical spine manipulative physiotherapy treatment on the pain and dysfunction of lateral epicondylalgia

    Pain

    (1996)
  • B. Vicenzino et al.

    Cardiovascular and respiratory changes produced by the lateral glide mobilisation of the cervical spine

    Manual Therapy

    (1998)
  • A. Wright

    Hypoalgesia post-manipulation therapy: a review of a potential neurophysiological mechanism

    Manual Therapy

    (1995)
  • A. Wright

    Recent concepts in the neurophysiology of pain

    Manual Therapy

    (1999)
  • M. Zusman

    Spinal manipulative therapy: review of some proposed mechanisms and a new hypothesis

    Australian Journal of Physiotherapy

    (1986)
  • W.J.J. Assendelft et al.

    The relation between methodological quality and conclusions in reviews of spinal manipulation

    Journal of the American Medical Association

    (1995)
  • B. Blackwood et al.

    The crossover study design and its clinical application

    Nurse Researcher

    (1998)
  • J.M. Bland et al.

    Matching

    British Medical Journal

    (1994)
  • Clinical guidelines for the physiotherapy management of persistent low back pain. Part 2. Manual therapy

    (2006)
  • S.M. Ellestad et al.

    Electromyographic and skin resistance responses to osteopathic manipulative treatment for low back pain

    Journal of the American Osteopathic Association

    (1988)
  • N.E. Foster et al.

    Management of non-specific low back pain by physiotherapists in Britain and Ireland

    Spine

    (1999)
  • G.L. Gebber et al.

    Differential patterns of spinal sympathetic outflow involving a 10-Hz rhythm

    Journal of Neurophysiology

    (1999)
  • G.L. Hardy et al.

    Inter and intratherapist reliability of passive accessory movement technique

    New Zealand Journal of Physiotherapy

    (1991)
  • W. Jänig et al.

    Neurophysiological analysis of target-related sympathetic pathways—from animal to human: similarities and differences

    Acta Physiologica Scandinavica

    (2003)
  • M.J. Kenney et al.

    Differential relationships among discharges of postganglionic sympathetic nerves

    American Journal of Physiology

    (1991)
  • L.C. Li et al.

    Physical therapy management of low back pain: an exploratory survey of therapist approaches

    Physical Therapy

    (2001)
  • Cited by (61)

    View all citing articles on Scopus
    View full text