Introduction: Several theories have been proposed to explain the therapeutic benefit of spinal manipulation (SM), one of which is the reflexogenic response, whereby there is thought to be a reflex reduction in pain, muscle hypertonicity and functional improvement.

Methods: 60 patients were randomised to receive a single high velocity low amplitude thrust or a sham manipulation, where a similar thrust was given to the subject, but applied non-specifically. After testing for reliability, physiological effects in a number of muscle groups was explored through assessment of pressure pain threshold (PPT) and muscle activity using algometry and surface electromyography (sEMG) respectively. The sEMG reflex response was recorded during the manipulation and a record of whether cavitation was achieved was recorded. PPT measurements were taken pre and post intervention over three experimental visits (each visit being a week apart).

Results: There were no statistically significant differences in the magnitude of the sEMG reflex response to a single SM compared to the sham. However at the third application a significantly larger sEMG reflex response was seen in the SM group compared to the sham manipulation, for multifidus (F=9.57, p=0.01) and gluteus maximus muscles (F=6.41, p=0.02). There were no associations between the size of the reflex response and any of the subject’s baseline characteristics or changes in pain at any time point.

Conclusion: It is unlikely SM influences pain and function via a muscular reflexogenic effect. It may be that the longitudinal change in the reflex response indicates a biomechanical change in one group.

Background: There is evidence that spinal manipulation (SM) has therapeutic benefit in the treatment of back pain. However, there is still poor understanding of the physiological mechanism by which it achieves its therapeutic benefit. In order to explore the mechanism of SM, this study explored it’s immediate anti-nociceptive effect, by measuring the pressure pain threshold (PPT) in spinal muscles pre and post SM, in subjects with low back pain.

Methods: A group of low back pain patients (n=60) were randomised into two groups, one received a SM to a dysfunctional segment in the lumbar spine. The second group received a sham procedure, where the patient was placed in a similar ‘wind up’ position, but the thrust applied non-specifically through the low back. Algometry measurements were taken over four spinal muscles (iliocostalis, multifidus, glutei and trapezius), before and after the manipulation or sham procedure.

Results: Paired t-tests for within group differences showed statistically significant differences for the SM group iliocostalis (p< 0.001) multifidus (p< 0.001) glutei (p< 0.001) and trapezius (p=0.20) with small to moderate effect size (0.60; 0.58; 0.36 & 0.20 respectively) small between group differences were also noted. There were no significant changes in PPT in any muscle in response to the sham procedure.

Conclusion: SM produced a statistically significant change in PPT with a small to medium effect size. No changes were observed in the sham and thus the active component of SM appears to be related to the specific manipulative thrust technique rather than to the general handling and positioning of the patient.

Introduction: Algometry has been shown to be an effective way of quantifying pressure pain threshold (PPT), although it’s reliability in assessing spinal muscle pain (excluding trigger points) has not been robustly analysed.

Method: Intra-rater test re-test reliability PPT assessment by algometry over the belly of four pairs of spinal muscles, (iliocostalis, multifidus, gluteus maximus and trapezius) in a healthy sample (80 assessments) was analysed. Healthy subjects were tested twice (within 15mins) on three occasions (separated by a week); 240 sets of assessments revealed good within-session reliability (ICC> .91) and good between session reliability (ICC> .87), with a relatively small measurement error (approximately 3kg/cm²) and no systematic difference within session or between sessions.

Conclusion: In conclusion, PPT assessment by algometry is a reliable, both within and between sessions, measure of a subject’s pain. This study provides further validity to the use of this measure as a suitable, convenient method of monitoring treatment effects.