Trip-specific training enhances recovery after large postural disturbances for which there is NO expectation.

PURPOSE: Informed consent usually provides foreknowledge of experimental methods that can potentially increase expectation of stimuli and, therefore, influence the response. We determined the effects of increased expectation and trip-specific training on the recovery response following a treadmill-delivered, trip-specific disturbance. To deliver unexpected disturbances, subjects were deceived during the informed consent process. The primary hypothesis was that the recovery response following an expected postural disturbance would be characterized by trunk kinematics that have been shown to decrease the likelihood of a fall, compared to following an unexpected postural disturbance. We further hypothesized that following an unexpected postural disturbance, the recovery response of the subjects who had completed a trip-specific training protocol would be more biomechanically favorable to recovery compared to those of subjects who had not received the training. METHODS: Young adults were randomized into Untrained or Trained groups. During the informed consent process, the purpose of the study was explained to subjects in both groups as being to determine the effect of trip-specific training on postural sway while performing an attention-demanding task. Untrained subjects completed two trials during which they minimized their postural sway. During the second trial, an unexpected disturbance was delivered while they performed the attention-demanding task. Trained subjects performed a pre-training postural sway trial, followed by the delivery of a series of expected, training disturbances. Finally, an unexpected disturbance was delivered while they minimized postural sway and performed the attention-demanding task. RESULTS: Expectation significantly improved trunk kinematics (p < .05). In addition, participation in the trip-specific training protocol following the unexpected disturbance the trunk kinematics of the Trained subjects were more biomechanically favorable to recovery than those of the Untrained subjects (p < .01). CONCLUSION: Improved trunk kinematics following trip-specific training may be independent of the extent to which the disturbance is expected.

Unilateral Discomfort Increases the Use of Contralateral Side during Sit-to-Stand Transfer.

Individuals with unilateral impairment perform symmetrical movements asymmetrically. Restoring symmetry of movements is an important goal of rehabilitation. The aim of the study was to evaluate the effect of using discomfort-inducing devices on movement symmetry. Fifteen healthy individuals performed the sit-to-stand (STS) maneuver using devices inducing unilateral discomfort under the left sole and left thigh or right sole and right thigh and without them. 3D body kinematics, ground reaction forces, electrical activity of muscles, and the level of perceived discomfort were recorded. The center of mass (COM), center of pressure (COP), and trunk displacements as well as the magnitude and latency of muscle activity of lower limb muscles were calculated during STS and compared to quantify the movement asymmetry. Discomfort on the left and right side of the body (thigh and feet) induced statistically significant displacement of the trunk towards the opposite side. There was statistically significant asymmetry in the activity of the left and right Tibialis Anterior, Medial Gastrocnemius, and Biceps Femoris muscles when discomfort was induced underneath the left side of the body (thigh and feet). The technique was effective in causing asymmetry and promoted the use of the contralateral side. The outcome provides a foundation for future investigations of the role of discomfort-inducing devices in improving symmetry of the STS in individuals with unilateral impairment.