Linking SM to Sensorimotor Dysfunction
There is important work showing that forces of the
magnitude of SM loads can stimulate proprioceptors in
the joints and muscles [37,38]. The approach in this
current study is to use SM as a tool to influence proprioceptive
input to spinal tissues and observe the
effects that input has on sensorimotor function. Thus,
this study may provide clues to the sensorimotor
mechanisms that underlie the observed functional deficits
associated with LBP, as well as the mechanism of
action of SM.
Postural Sway
The capability of a person to maintain balance in an
upright posture requires a complex integration of accurate
sensory input and precisely coordinated motor output
[39]. Sensory inputs include the vestibular system,
the visual system and the proprioceptors in muscles and
joints. Muscle activity must be simultaneously controlled
at three levels to achieve stability: spinal reflex, brain
stem balance and cognitive programming [40]. Disturbances
to the neuromuscular system can affect the
degree of efficiency and accuracy with which posture is
maintained [41].
LBP patients have impaired postural stability compared
to healthy individuals [42-46]. It is hypothesized
that the reduced proprioceptive acuity derived from
muscle or joint mechanoreceptors can be a cause of
altered postural sway [47]. Another theory is that LBP
patients have impaired short-term memory that leads to
delays in processing postural control information and
increased sway [48].
Response to Sudden Impact Loads
In the flow of everyday living, people sometimes experience
sudden and unanticipated forces, such as stepping
off a curb unexpectedly. An individual’s central nervous