The effect of changes in foot sensation on plantar pressure and muscle activity

Objective. Purpose was (a) to quantify changes that occur in plantar pressure following attenuation of sensory input from the plantar surface of the foot, and (b) to quantify the resultant changes in motor output as measured by the changes of muscular activation. Design. Cross-sectional design in a laboratory setting. Background. The importance of afferent feedback to controlling gait has been demonstrated in quasi-static situations, and with animal models. However, the effects and functional significance of sensory feedback from cutaneous receptors in the plantar surface of the foot during walking are still not resolved. Methods. Sensory thresholds were deter-mined for the plantar surface of the foot. Sensory feedback was reduced with an ice intervention. Three altered sensory states were tested: whole foot, forefoot and rearfoot ice exposure. Plantar pressure distributions and lower extremity muscle patterns were collected while walking before and after ice exposure. Results. Exposure to ice increased vibration thresholds to low and high frequency vibrations. Peak pressure and pressure-time integral were significantly higher in areas of normal sensitivity and lower at the insensate areas. The center of pressure underfoot shifted away from areas of decreased sensitivity when sensory input is reduced from a portion of the foot. Muscle patterns were significantly altered when sensory feedback was changed. Conclusions. By altering sensory feedback, one can alter gait kinetics and muscular activation patterns. Cutaneous feedback is important in the regulation and modification of gait patterns, and sensory input needs to be included in any model that attempts to predict motion.