Background and purpose: Spinal mobilization is commonly used to relieve pain and assist recovery of mobility in individuals with low back pain. Fundamental to this concept is the belief that spinal mobilization will influence the mechanical properties of the symptomatic motion segment. The objective of the present study was to examine the segmental effects of a standardized mobilization procedure on the posteroanterior (PA) stiffness of the lumbar spine.
Method: Audio and visual feedback was used to train a physiotherapist to perform PA mobilization at a consistent load and frequency. After training, twenty-four subjects without low back pain were recruited for the intervention phase of the study. The spinal posteroanterior mobilization (SPAM) apparatus was used to measure the PA stiffness of the lumbar spine at three measurement sites (L1, L3 and L5). The trained physiotherapist then applied the standardized PA mobilization technique via the L3 spinous process for two minutes. Following mobilization, PA stiffness was measured three times at the three locations.
Results: The physiotherapist was able to apply a standardized mobilization with a mean force of 146 N (standard deviation (SD) 8 N) at a frequency of 1.5 Hz. The first trial on each assessment demonstrated a pre-condition effect. Two minutes' PA mobilization resulted in no significant change in the PA stiffness of the lumbar spine at the level to which the mobilization was applied, or at the L1 and L5 segments. The 95% confidence intervals (CI) of the difference in PA stiffness before and after testing included zero at each measurement site.
Conclusions: Clinicians should pre-condition the spine when assessing PA stiffness both before and after interventions. A standardized mobilization of 150 N at 1.5 Hz for two minutes had no segmental effect on spinal PA stiffness. Subsequent studies need to consider other mechanisms that may contribute to the changes that occur after PA spinal mobilization.