Yong-Jun Piao

Development of Abnormal Gait Detection and Vibratory Stimulation System on Lower Limbs to Improve Gait Stability

The purpose of this study is to develop an abnormal gait detection algorithm and a vibratory stimulation system on a lower limb to improve gait stability and prevent falls. The system consists of a gait measurement module, an abnormal gait detection module, and a vibratory stimulation module. The gait measurement module measures the vertical acceleration of the ankle during walking using an accelerometer. The measured acceleration values are sent to a portable microcontroller, which controls vibratory stimulations to the ankles based on an algorithm that detects the peak acceleration values. If the acceleration peaks are found to occur irregularly, the abnormal gait detection algorithm activates the vibratory stimulation module. To determine the effect of vibratory stimulations under dynamic condition, this study investigated the contribution of ankle muscle proprioception on the control of dynamic stability and lower limb kinematics while walking using vibratory stimulation to alter the muscle spindle output of individuals’ left lower limb. Vibrators were attached to the left ankle joint (tibialis anterior, triceps surae). Participants were required to walk along a travel path and step over an obstacle placed in their way. There were four task conditions; an obstacle (10%, 20%, and 30% of the participants’ height) was positioned at the midpoint of the walkway, or the participants’ walking path remained clear. For each obstacle condition, participants experienced either no vibration, or vibration of the tibialis anterior muscle and the triceps surae muscle of the left lower limb. Vibration began upon detection of an abnormal gait and continued for one second. Vibrating the ankle muscles of the left lower limb while stepping over an obstacle resulted in significant changes in COM behavior on both the anterior/posterior (A/P) and medial/lateral (M/L) planes. The results provide strong evidence that the primary endings of the ankle muscle spindles play a significant role in the control of posture and balance during the swing phase of locomotion by providing information on the movement of the body’s COM with respect to the support foot.

Experimental Studies on the Training of Postural Control Using an Unstable Platform

We performed experimental studies on the training of postural control using a training system which consists of an unstable platform, a computer, a computer interface, a monitoring device, and training programs. Using this system with the training programs that we have developed, we performed a variety of experiments of training the abilities of postural control of subjects. To evaluate the effects of the training, the parameters on how long a subject can maintain a focus on a target, the mean absolute deviation of the trace, and the fatigue of the muscles in lower limbs were measured. The experimental results showed that the training system can improve the ability of postural control of the subject. Therefore, the training system could be applied to clinical rehabilitation training for posture control as a new balance training system

Development of Rehabilitation Training System Using Unstable Flatform with Magneto-Rheological Damper

The purpose of this paper was to develop a rehabilitation training system which is controlled by electric currents to the Magneto-Rheological dampers system. This system provided the function for the training of the unbalance of the lower extremities. 10 subjects executed the tracing and moving exercises which are presented through the display monitor and confirmed own the capability of performance on the task. The electromyographies of the four muscles in lower extremities were recorded and analyzed in the time and frequency domain the muscles of interest were rectus femoris, biceps femoris, gastrocnemius, tibialis anterior. The experimental results showed that subjects had a task under feedback mode then subjects improve the capability of performance, increasing the in time, decreasing the out time and the distance of body shift. The moving average EMG, spectral energy of four muscle is lower the feedback mode than the constant mode. This could aid the hemiplegic patients to train more easily.

Analysis of temporal perception for audio-visual stimulation

In situations of perception, researches about audio-visual stimulation have generally found that audition prevails over vision in temporal perception, whereas vision is dominant over audition for spatial perception. Modality appropriateness to a given task generally determines the direction of inter-modality effect. However, we found a reverse effect in some situations where a change in the frequency of visual stimulation was associated with a perceived change in the frequency of auditory stimulation. The physical stimulus didn’t always accord with the perception. Thus, we performed two different experiments to certain the influence of the orientation between auditory and visual stimulus, the color of visual stimulus and sex difference of testee with normal people. In first experiment, 12 participants were asked to judge the change in the frequency of audio-visual stimulation using a visual flicker and auditory flutter stimulation in the condition of same auditory and visual orientation. When auditory temporal cues were presented, the change in the frequency of the visual stimulation was associated with a perceived change in the frequency of the auditory stimulation apart from different or same visual and auditory orientation. In second experiment, 30 men and women were asked to judge the change in the frequency of audio-visual stimulation using a color of visual flicker and auditory flutter stimulation. The colors for visual stimulus are red and green. The accuracy of perception drops down in red. Men and women showed similar perceptual tendency however in case of women, the value of standard deviation is larger than that of men. These results imply that audiovisual asymmetry effects are influenced by the cues of visual and auditory information, such as the orientation between auditory and visual stimulus, the color of visual stimulus.

Development of a Somatosensory Stimulation System for the Improvement of Postural Stability

This paper proposes a somatosensory stimulation system for the improvement of postural stability using vibration as somatosensory stimulation. This system consists of vibratory stimulation and postural response measurement. To evaluate this system, the center of pressure(COP) was closely observed in turn with simultaneous or separate mechanical vibratory stimulations to flexor ankle muscles (tibialis anterior, triceps surae) and two plantar zones on both feet while standing on a stable and an unstable support. The simultaneous vibratory stimulations cleared influenced postural stability and the effects of vibrations were higher with the unstable support. In separate vibratory stimulations, the extent of the COP sway reduced when the direction of the vibratory stimulations and that of the inclination of body coincided for flexor ankle muscle stimulations. In the contrary, the extent of the COP sway increased when the direction of the stimulations and that of body inclination coincided for plantar zone stimulations. These results can be useful for the development of rehabilitation systems that utilizes somatosensory inputs for postural balance.