Do Clinical Models Add Enlightment or Confusion to the Identification of Control Pathways?

Speculations about the contribution of sensory feedback to balance corrections have been strongly influenced by the clinical observations of balance disorders following vestibular or proprioceptive sensory loss. Unfortunately, those speculations have been more influenced by early rudimentary concepts of postural control tested under a limited set of circumstances. For example, from examinations of only lower-leg balance-correcting responses to slow support-surface perturbations in the pitch plane. Such focused protocol would immediately exclude any valid modeling of trunk control which, unlike the ankle, is more unstable in pitch and roll planes. In order to draw a tighter link between new conceptual schemes about balance control pathways and clinical models, it is essential that the biomechanical consequences of a disease state and muscle responses underlying instability of the trunk be considered.