Effects of altered sensory information during posture and gait: A developmental perspective.

In young adults, the role of Ia primary muscle spindles from the gastroc-soleus have been investigated extensively during quiet standing and are considered important contributors to the maintenance of quiet stance. The Ia primary muscle spindles may play a limited influence on the modulation of muscle activity during the stance phase of gait for young adults. An investigation into the contribution of Ia primary muscle spindles to the control of postural stability and gait in children between the ages of 5--7 and 9--11 years of age was completed. During the postural task afferent information was manipulated via unilateral tendon vibration with and without visual information. In general, the perturbation of the proprioceptive information during the postural control task was more destabilizing to the children compared to the young adults, particularly when vision was occluded. Based on the current findings it was not definitive that peripheral factors contributed significantly to postural differences observed between children and adults. However, several centrally mediated factors, such as difficulty reweighing sensory inputs, delayed muscle onsets and inefficient muscle activity, were considered attractive and plausible explanations contributing to the differences observed between children and adults. During the walking task, vision was always available and vibration was briefly applied during the swing and stance phases or continuously throughout the gait cycle. The principal findings related to the walking study involved the modulation of plantarflexor muscle activity during the stance phase for the children and not the young adults, and a greater number of alterations to the walking characteristics during the continuous vibration condition for the children when compared to the young adults. The modulation of muscle activity during the stance phase for the children suggests peripheral factors specific to the phasic gating of sensory information appears to be different for children than young adults during walking. While the differences observed between the children and young adults during the continuous vibration condition are suggestive of difficulties with centrally mediated processes potentially related to the ability to flexibility manage, extract, and process afferent inputs.PhDBiological SciencesHealth and Environmental SciencesKinesiologyPhysiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/125829/2/3224696.pd