Persons with recurrent low back pain exhibit a rigid postural control strategy

Abstract

Persons with recurrent low back pain (LBP) have been observed to have altered proprioceptive postural control. These patients seem to adopt a body and trunk stiffening strategy and rely more on ankle proprioception to control their posture during quiet upright standing. The aim of this study is to determine the effect of changing postural condition (stable and unstable support surface) on postural stability and proprioceptive postural control strategy in persons with recurrent LBP. Postural sway characteristics of 21 persons with recurrent LBP and 24 healthy individuals were evaluated in upright posture with or without standing on "foam" for the conditions as follows: (1) control (no vibration); (2) vibration of the triceps surae muscles; (3) paraspinal muscle vibration; (4) vibration of the tibialis anterior muscles. Vision was occluded in all conditions except for one control trial. All trials lasted 60 s. Vibration (60 Hz, 0.5 mm), as a potent stimulus for muscle spindles, was initiated 15 s after the start of the trial for a duration of 15 s. Persons with recurrent LBP showed significantly different postural control strategies favoring ankle muscle proprioceptive control (ratio closer to 1) instead of paraspinal muscle proprioceptive control (ratio closer to 0) for both standing without foam (ratio ankle muscle/paraspinal muscle control = 0.83) (P < 0.0001) and on foam (ratio ankle muscle/paraspinal muscle control = 0.87; P < 0.0001) compared to healthy individuals (0.67 and 0.46, respectively). It is concluded that young persons with recurrent LBP seem to use the same proprioceptive postural control strategy even in conditions when this ankle strategy is not the most appropriate such as standing on an unstable support surface. The adopted proprioceptive postural control strategy might be effective in simple conditions, however, when used in all postural conditions this could be a mechanism to undue spinal loading, pain and recurrences.

Fig. 1

a Experimental setup: Condition 1—triceps surae muscle vibration trial. b Experimental setup: Condition 2—paraspinal muscle vibration trial

Fig. 2

Means and standard deviations of the relative proprioceptive weighting triceps surae muscle/lumbar multifidus muscle of healthy persons and persons with recurrent low back pain when standing on a stable support surface (white) and on an unstable support surface (striped pattern). Higher numbers mean more use of proprioceptive input from the ankle muscles

Fig. 3

a Means and standard deviations of the relative proprioceptive weighting triceps surae muscle/lumbar multifidus of sub-classified persons with low back pain when standing on a stable support surface (white) and on foam (striped pattern). b Means and standard deviations of the relative proprioceptive weighting triceps surae muscle/lumbar multifidus of sub-classified healthy persons when standing on a stable support surface (white) and on foam (striped pattern)