Research Review By Dr. Stanley Bacso©


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Date Posted:

May 2011

Study Title:

Immediate effects of lumbar spine manipulation on the resting and contraction thickness of Transversus Abdominis in asymptomatic Individuals


Puentedura EJ et al.

Author's Affiliations:

University of Nevada - Las Vegas (UNLV), School of Allied Health Science, Department of Physical Therapy, USA.

Publication Information:

Journal of Orthopaedic & Sports Physical Therapy 2011; 41(1): 13-21.

Background Information:

For some time now, it has been suggested that the Transversus Abdominis (TrA) muscle plays a role in spinal stability and control in asymptomatic individuals and low back pain (LBP) patients (1-5). More specifically, original research in this area revealed delays in TrA activation with upper limb movements or trunk perturbation in LBP subjects (this research is from the Queensland, Australia group – Hides, Richardson et al.). Further, previous studies have shown immediate decrease in resting TrA thickness and an increase in contraction thickness following lumbar Thrust Joint Manipulation (SMT) in patients with low back pain. This however has not been evaluated in healthy individuals. (EDITOR’S NOTE: Overall, the importance of the TrA remains controversial. Some world renowned experts – including Dr. Stu McGill – suggest that the entire corset of abdominal muscles together is most important, rather than the isolation of the TrA. This has led to ongoing debate about rehabilitation and treatment approaches. This has yet to be settled and there are likely components of both main approaches [‘bracing’ and ‘hollowing/TrA-specific rehab] that are applicable in certain patient populations.)

The objective of this study is to determine if lumbar SMT results in changes to the resting and contraction thickness of the TrA muscle in healthy individuals. The proposed approach was to facilitate isolated contraction of the TrA by way of the employing an Abdominal Drawing-In Maneuver (ADIM) (6-8). While acknowledging that muscle thickness changes of the TrA have been observed in ultrasound imaging of patients with low back pain following lumbar manipulation (9), this study examined the changes in TrA muscle thickness at rest and during ADIM following lumbar SMT in asymptomatic individuals. The results may provide further information as to the therapeutic effectiveness, the exact neurological mechanism and physiological effects of manipulation therapy.

Pertinent Results:

Put simply, the results of this particular study indicate that there was no difference in thickness of the TrA muscle at rest or during contraction both prior to, and following, either the SMT or the sham procedure in healthy individuals. In other words, there was no interaction observed between the treatment & muscle thickness at rest or in the contracted state.

Clinical Application & Conclusions:

This study raises questions pertaining to the mechanism of action for spinal manipulation, and the role of TrA in the pathology of low back pain. Although there is evidence to support the clinical effectiveness of joint manipulation in a select group of patients with low back and neck pain, the precise mechanism(s) responsible for this benefit still remains unclear. In general, the proposed mechanisms for SMT involve neurophysiological and reflexogenic responses at the joint mechanoreceptor and muscle spindle level. Further, spinal manipulation is thought to lead to pain modulation as well as attenuation of motor activity and/or normalization of muscular coordination as well as kinematic muscle firing patterns (15-17). This may assist in disrupting the “cycle of pain” (i.e., spasm-ischemia-pain-spasm cycle) as well as allowing for the strengthening and conditioning of the stabilizing musculature in this region (16).

The results of this particular study indicated that there was no difference in the thickness of the TrA muscle at rest or during contraction whether it followed a thrust joint manipulation or sham procedure in healthy individuals. These findings were in contrast to those studies that found differences in both the resting and contracted thicknesses of TrA muscles following manipulation in patients with acute low back pain (9, 18). These researchers postulated that changes in the thickness of these muscles might be due to segmental and/or supra-segmental effects afforded by manipulation (19), including neurophysiological and hypo-analgesic effects significantly different from that of placebos noted in other studies (20-25).

The interesting difference was that in this study the participants did not have any low back pain. As such, it was argued that inhibitory descending influences such as pain modulation would have had little effect on asymptomatic individuals - whereas these influences and the physiological results (i.e. changes in the TrA) would have been more noticeable in symptomatic patients.

An additional consideration was that the immediate effects of SMT in asymptomatic individuals were studied using needle electromyography and assessed using H-reflex (15, 16) to examine motor neuron activity. The results indicate that the EMG latencies were found to occur within 50-200 milliseconds after the manipulative thrust, and lasted only 100-400 milliseconds. As such, it is possible the parameters of this study were unable to measure changes in the muscle tissue even if significant influences were present, albeit only detectable for a short period of time.

Study Methods:

This study used 35 healthy (no LBP) participants (men and women, average age ~25) who were randomly assigned to joint manipulation or sham manipulation treatment. All of the participants were instructed on the abdominal draw-in (ADIM) maneuver. Data was analyzed to test for two hypotheses:
  1.  the resting thickness of TrA following TJM would differ from that following sham procedure; and
  2.  contracted thickness of TrA following TJM would differ from that following a sham procedure
Individuals were assigned into two groups, one receiving lumbar SMT at the time of their first visit and a sham manipulation (i.e. non-thrust) on the subsequent visit. The second group received these interventions in reverse order.

Ultrasound imaging was used to assess the thickness of the TrA muscle. This has been shown to be a reliable method for assessing thickness changes of the anterolateral abdominal muscles (10, 11). Once assigned to one of the two groups, the individuals were instructed to properly perform the ADIM maneuver and produce isometric TrA contraction (9, 12, 13). The individuals performed the ADIM in the quadruped position (neutral spine) five times, holding each contraction for 10 seconds. Then, the individual was placed in the prone position with a pillow underneath the abdomen and instructed to continue the exercise - gently lifting the weight of the lower abdomen off the pillow without moving the spine for another set of five for 10 seconds each.

Ultrasound images were obtained both pre-treatment and post-treatment; aligned perpendicular to the anterolateral abdominal musculature and measurement of the TrA muscle taken after normal exhalation. This was taken with the patient positioned in the supine hook-lying position. A total of 12 images were obtained of the right anterolateral abdominal wall for each participant: three pre-treatment relaxed, three pre-treatment contracted, three post-treatment relaxed, and three post-treatment contracted. The participants returned one-week later to undergo the alternate treatment and a second set of 12 ultrasound still images were obtained for each individual.

SMT was delivered utilizing a high-velocity end-range rotation thrust to the lumbar spine with the patient side-lying. The thrust was applied with the forearm against the pelvis in a downward direction by applying exaggerated pelvic rotation. The stabilizing arm held the axillary region and did not apply thrust (stabilization only) - this appeared very reminiscent of the, “lumbar roll” maneuver used in conventional chiropractic Diversified manual technique. The sham intervention included a similar set up maneuver with the patient in the side-lying position but with both hips and knees flexed to 45°. The researchers then applied a Maitland Grade 1 oscillation for lumbar rotation (14). No cavitation occurred or was obtained during the sham treatment.

To assess the relationship of the manipulation on TrA muscular thickness analysis of variance (ANOVA) was conducted for muscle thickness at rest and for muscle thickness during the contracted state.

Study Strengths/Weaknesses:

As indicated previously, the responses may have occurred too quickly to be observed via ultrasound imaging, which would be conducted several minutes after the manipulative thrust was applied. Electromyography latencies of times between 50-200 ms after the manipulation have been measured, which lasted only 100-400 ms. This could be problematic for the detection of any tangible or lasting TrA change. This could also be considered an inherent weakness in the design of the study as it might be incapable of detecting any significant changes in TrA muscle even if it had occurred.

An additional consideration is that the participants might not have been performing the ADIM maneuver in the same manner and with the same consistency. There was neither a measurement of muscle contraction nor electromyography outcomes to verify the consistency and reliability of the performed abdominal contraction (ADIM) maneuver. This is significant as previous studies had indicated a strong relationship between EMG signal amplitude (i.e. the ‘strength’ of the contraction) and changes in the TrA muscle thickness (26, 27). It was also noted that the ultrasound imaging measures might not be useful in determining very subtle changes in the muscle thickness (27).

It was also noted that this report did not examine thickness changes of associated musculature more closely connected with the postural mechanical effects of SMT, such as the changes in lumbar multifidus following the treatment interventions.

By the authors’ own admission, their results also indicated that the sample size might have been too small for this type of study. The current data could not provide reasonable estimates of expected outcomes in order to prognosticate future studies or to provide sufficient extrapolative measures.

Additional References:

  1. Hodges P et al. Preparatory Trunk Motion Accompanies Rapid Upper Limb Movement. Exp Brain Res. 1999, 124: 69-79.
  2. Hodges P, Richardson C. Contraction of the Abdominal Muscles Associated with Movement of the Lower Limb. Phys Ther. 1997, 77:132-142.
  3. Hodges P, Richardson C. Feed-forward Contraction of Transfers of Dominance Is Not Influenced by the Direction of Our Movement. Exp Brain Res. 1997, 114: 362-370.
  4. Hodges P, Richardson C. Relationship between Limb Movement Speed and Associated Contraction of the Trunk Muscles. Ergonomics. 1997, 40; 1220-1230.
  5. Hodges P, Richardson C. Transversus Abdominis And the Superficial of Domino Muscles Are Controlled Independently in a Postural Task. Neurosci Lett. 1999, 265: 91-94.
  6. O’Sullivan P et al. Evaluation of Specific Stabilizing Exercises in the Treatment of Chronic Low Back Pain with Radiologic Diagnosis of Spondylitis and Spondylolisthesis. Spine 1997, 22; 2959-2967.
  7. O'Sullivan P et al. Altered Abdominal Muscle Recruitment in Patients with Chronic Back Pain Following a Specific Exercise Intervention. J Orthop Sports Phys Ther. 1998, 27: 114-124.
  8. Richardson C et al. Therapeutic Exercise for Lumbopelvic Stabilization: A Motor Control Approach for the Treatment and Prevention of Low Back Pain (Second Edition) London, UK: Churchill Livingstone, 2004.
  9. Gill N, Teyhan D. Improved Contraction of the Transversus Abdominis Immediately Following Spinal Manipulation: a Case Study Using Real-Time Ultrasound Imaging. Man Ther. 2007, 12: 280-285.
  10. Henry S, Westervelt K. The Use of Real-Time Ultrasound Feedback in Teaching Abdominal Hollowing Exercises to Healthy Subjects. J Ortho Sports Phys Ther. 2005, 35: 338-345.
  11. Koppenhaver S et al. Reliability of Rehabilitative Ultrasound Imaging of the Transversus Abdominis and Lumbar Multifidus Muscles. Arch Phys Med Rehabil. 2009, 90: 87-94.
  12. Hides J et al. Ultrasound Imaging Assessment of Abdominal Muscle Function during Drawing in of the Abdominal Wall: An Intrerater Reliability Study. J Ortho Sports Phys Ther. 2007, 37: 480-486.
  13. Teyhen D et al. The Use of Ultrasound Imaging of the Abdominal Drawing in Maneuver in Subjects with Low Back Pain. J Ortho Sports Phys Ther. 2005, 35: 346-355.
  14. Maitland G et al. Maitland's Vertebral Manipulation (7th Edition). Philadelphia, PA: Elsevier Butterworth-Heinemann, 2005.
  15. Herzog W et al. Electromyographic Responses of Back and Limb Muscles Associated with Spinal Manipulative Therapy. Spine 1999, 24: 146-152.
  16. Murphy B et al. Sacroiliac Joint Manipulation Decreases the H-Reflex. Electromyogr Clin Neurophysiol. 1995, 35: 87-94.
  17. Pickar J. Neurophysiological Effects of Spinal Manipulation. Spine J. 2002, 2: 357-371.
  18. Raney N et al. Observed Changes in Lateral Abdominal Muscle Thickness after Spinal Manipulation: A Case Series Using Rehabilitative Ultrasound Imaging. J Ortho Sports Phys Ther. 2007, 37: 472-479.
  19. Bialosky J et al. The Mechanisms of Manual Therapy in the Treatment of Musculoskeletal Pain: a Comprehensive Model. Man Ther. 2009, 14: 531-538.
  20. Bialosky J et al. The Influence of Expectation on Spinal Manipulation Induced Hypoalgesia: An Experimental Study and Normal Subjects. BMC Musculoskelet Disord. 2008, 9: 19.
  21. Fernandez C et al. Immediate Effects On Pressure Pain Threshold Following a Single Cervical Spine Manipulation in Healthy Subjects. J Orthop Sport Phys Ther. 2007, 37: 325-329.
  22. Fryer G et al. The Effect of Manipulation and Mobilization on Pressure Pain Thresholds in the Thoracic Spine. J Osteopath Med. 2004, 7: 8-14.
  23. Oliveria-Campelo, N et al. The Immediate Effects of Atlanto-Occipital Joint Manipulation and Suboccipital Muscle Inhibition Technique on Active Mouth Opening and Pressure Pain Sensitivity over Latent      Myofascial  
  24. Trigger Points in the Masticatory Muscles. L Orthop Sports Phys Ther. 2010, 40: 310-317.
  25. Ruis M et al. Changes in Pressure Pain Sensitivity in Latent Myofascial Trigger Points in the Upper Trapezius Muscle after a Cervical Spine Manipulation in Pain-Free Subjects. JMPT. 2007, 30: 578-583.
  26. Terrett A, Vernon, H. Manipulation and Pain Tolerance. A Controlled Study of the Effect of Spinal Manipulation on Paraspinal Cutaneous Pain Tolerance Levels. Am J Phys Med. 1984, 63: 217-225.
  27. McMeeken J et al. The Relationship between EMG and Change in Thickness of Transversus Abdominis. Clin Biomech. 2004, 19: 337-342.
  28. Hodges P et al. Measurement of Muscle Contraction with Ultrasound Imaging. Muscle Nerve. 2003, 27: 682-692.