An Investigation into the Role of Tactile Feedback in the Neuromuscular Control of Spine Movement
The spine requires refined, adaptable neuromuscular control to ensure proper function. To facilitate this control, many sensory systems contribute feedback about the position and movement of one's body. These systems include feedback from muscles, tendons, ligaments, as well as the skin. The overall aim of this PhD dissertation was to investigate the influence of tactile (skin) sensory feedback on the neuromuscular control of the spine. To address this aim, four experiments were completed. In Experiment #1 the effect of decreased tactile sensitivity on spine neuromuscular control was investigated. Participants had the skin of their back anaesthetized (numbed). When compared to a control group, the anesthesia resulted in a significant impairment in skin sensitivity. However, this reduction had negligible impact on spine neuromuscular control. In Experiments #2 and #3, the influence of spine flexion-extension posture on skin structure and tactile sensitivity were investigated, respectively. For Experiment #2 participants were required to adopt extended, neutral or flexed spine postures during which measures of skin stretch, thickness and hardness were taken. The results demonstrated that spine posture significantly influenced each measure of skin structure. In Experiment #3 participants were asked to adopt the same three postures, during which measures of touch sensitivity, spatial acuity and skin stretch sensitivity were obtained. The results suggested that posture-mediated changes in skin structure (Experiment #2) significantly influenced the sensitivity to tactile stimuli. In Experiment #4, the utility of skin stretch feedback to facilitate adjustments in spine movements was investigated. If participants perceived skin stretching at specific regions of the back, they were instructed to adjust their spine flexion movement to minimize this sensation. These results are the first to demonstrate the utility of tactile information to evoke a redistribution of flexion motion across spine subsections (e.g. thoracic/lumbar) or intervertebral joints. Combined, Experiments #1-4 suggest that tactile feedback is a supplementary resource which can be used in the neuromuscular control of spine movement. When tactile feedback is diminished, neuromuscular control appears unaffected (Experiment #1). When pertinent posture-mediated (Experiments #2 and #3) feedback is provided, it can be interpreted to evoke a re-distribution of flexion movement across the spine (Experiment #4).