Muscle testing response to provocative vertebral challenge and spinal manipulation: a randomized controlled trial of construct validity.
OBJECTIVE
To evaluate the relationship of muscle strength response to a provocative vertebral challenge and to spinal manipulation.


METHODS
Prospective double-blind randomized controlled trial: crossover and between subjects designs.


METHODS
Laboratory: Center for Technique Research.


METHODS
Sixty-eight naive volunteers from the student body, staff and faculty of the college.


METHODS
Provocative vertebral challenge: standardized 4-5 kg force applied with a pressure algometer to the lateral aspects of the T3-12 spinous processes.


METHODS
manual high velocity low amplitude adjustment or switched-off activator sham.


METHODS
Piriformis muscle response was defined in two ways: reactivity (a decrease in muscle resistance, yes or nor, following a vertebral challenge); responsiveness (the cessation of reactivity following spinal manipulation). Relative response attributable to the maneuver (RRAM): the percent of an outcome attributable to the challenge or adjustment itself.


RESULTS
Average RRAM = 16% reactivity to vertebral challenge; average RRAM = 0% responsiveness to spinal manipulation. Six to 10% of muscle tests were positive regardless of examiner, previous finding or intervention.


CONCLUSIONS
For the population under investigation, muscle response appeared to be a random phenomenon unrelated to manipulable subluxation. In and of itself, muscle testing appears to be of questionable use for spinal screening and post-adjustive evaluation. Further research is indicated in more symptomatic populations, different regions of the spine, and using different indicator muscles.
Haas
M
M
Research Department, Western States Chiropractic College, Portlan, OR 97230-3099.
Peterson
D
D
Hoyer
D
D
Ross
G
G
D000328:Adult; D015982:Bias; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008349:Manipulation, Orthopedic / Q000379:methods*; D009119:Muscle Contraction; D015203:Reproducibility of Results; D013122:Spinal Diseases / Q000503:physiopathology; D013131:Spine / Q000502:physiology*