Mj. Simmonds et al., USE OF A SPINAL MODEL TO QUANTIFY THE FORCES AND MOTION THAT OCCUR DURING THERAPISTS TESTS OF SPINAL MOTION, Physical therapy, 75(3), 1995, pp. 212-222
Background and Purpose. Despite the widespread use of spinal mobilizat
ion, little is known about the forces used or the accuracy of therapis
ts in estimating the forces they use in administering the technique. T
he purposes of this study were to quantify the forces used and to dete
rmine the accuracy of therapists in applying forces on a mechanical mo
del. Subjects. Ten physical therapists participated. Methods. A spinal
model was used to measure applied force and displacement under differ
ent conditions of stiffness. The therapists applied oscillatory poster
oanterior mobilizations to the model under three different conditions
of stiffness. Results. Mean peak forces across grades and stiffness le
vels ranged between 57.59 and 178.27 N. The forces were generally lowe
r in the least stiff condition. Displacement varied with stiffness and
mobilization grade. In the least stiff condition, the mean displaceme
nt varied between 2.25 and 3.45 mm for grades 1 to 4, respectively. Co
nclusion and Discussion. Intertherapist variability was high, and ther
e was a systematic bias in underestimating the magnitude of applied fo
rce and in overestimating motion. The variability in force application
and the general overestimation of motion detection may explain the po
or reliability of measurements obtained with clinical tests based on m
otion palpation.