Abstract
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.
Correspondence should be addressed to SBPR at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE, England.
