Kazunori Yamazaki

The Relationship between Physical Function and Postural Sway during Local Vibratory Stimulation of Middle-aged People in the Standing Position

[Purpose] The purpose of this study was to examine the relationship between physical function and postural sway during local vibratory stimulation of middle-aged subjects in an upright position. [Subjects] The subjects were 25 healthy community-dwelling middle-aged people. [Methods] We measured postural sway using a Wii board while vibratory stimulations of 30, 60, or 240 Hz were applied to the subjects’ lumbar multifidus or gastrocnemius muscles. Physical function was evaluated by 5-m usual gait speed and grip strength. [Results] Gait speed was strongly correlated to the anteroposterior body sway in the upright position during 30 Hz gastrocnemius muscles vibration (GMV). [Conclusion] Postural sway during 30 Hz GMV was strongly associated with gait speed and showed a posterior displacement. These findings show that the lower leg’s response to balance control under 30 Hz proprioceptive stimulation might be a good indicator of declining gait function.

Fundamental study on evaluation of rotator cuff function using three-dimensional force display robot

The final aim of our research is to develop an evaluation system of rotator cuff function quantitatively using the three dimensional force display robot. The rotator cuff is made up of four inner muscles that act to stabilize the shoulder. Because of inner muscles, it is difficult to evaluate rotator cuff function directly. In this paper we perform three fundamental experiments to develop new evaluation methods of rotator cuff function. In the evaluation methods isotonic force is measured in various positions of an upper limb by using the force sensor, and muscular activity is measured by surface electromyography. The differences between the healthy shoulder and the disabled shoulder were found by the new proposed evaluation methods. From the results of experiments, the availability of the proposed methods is verified.

Relationship between paraspinal muscle cross-sectional area and relative proprioceptive weighting ratio of older persons with lumbar spondylosis.

[Purpose] The purpose of this study was to examine the relationship between the paraspinal muscle cross-sectional area and the relative proprioceptive weighting ratio during local vibratory stimulation of older persons with lumbar spondylosis in an upright position. [Subjects] In all, 74 older persons hospitalized for lumbar spondylosis were included. [Methods] We measured the relative proprioceptive weighting ratio of postural sway using a Wii board while vibratory stimulations of 30, 60, or 240 Hz were applied to the subjects’ paraspinal or gastrocnemius muscles. Back strength, abdominal muscle strength, and erector spinae muscle (L1/L2, L4/L5) and lumbar multifidus (L1/L2, L4/L5) cross-sectional areas were evaluated. [Results] The erector spinae muscle (L1/L2) cross-sectional area was associated with the relative proprioceptive weighting ratio during 60Hz stimulation. [Conclusion] These findings show that the relative proprioceptive weighting ratio compared to the erector spinae muscle (L1/L2) cross-sectional area under 60Hz proprioceptive stimulation might be a good indicator of trunk proprioceptive sensitivity.

Improvement of Knee Flexion and Extension Simulation Accuracy in KneeRobo

In a previous paper, we reported on the initial development of KneeRobo, which replicates knee joint troubles experienced by patients in order to enable students studying to become physical or occupational therapists to gain practical training/testing virtually. We also developed a control algorithm that enabled KneeRobo to realize involuntary internal/external rotation during knee flexion and extension. However, it is well known that in addition to internal/external rotation, abduction/adduction also occurs involuntarily during knee flexion and extension. Consequently, this paper proposes a new control method that improves the simulation accuracy of KneeRobos knee joint movements. This is accomplished by developing a control algorithm and designing a pulley arrangement that facilitates realization of involuntary movements such as internal/external rotation and abduction/adduction during knee flexion and extension by KneeRobo. The results of experimental comparison with the actual knee joint movements of a healthy person confirm that the knee joint movements simulated by the improved KneeRobo are accurate.

Postural Sway Response to Local Vibratory Stimulation in Young, Middle-aged and Elderly People in Standing Position

We investigated the postural sway in response to local vibratory stimulation applied to young, middle-aged and elderly people in the standing position. For this purpose we developed a variable-frequency vibratory stimulation device and measured the postural sway using a gravicorder. As a result, when the vibratory stimulation was applied to the gastrocnemius muscles, the center of pressure moved backward in all subject groups. We found that elderly people with low back pain may perform balance control using their trunks more than their lower legs.

Development of rehabilitation support system for lower limbs for recovery and quantitative evaluation of proprioception

Proprioception should be necessary for the trunk balance and skillful movement. However, proprioception deteriorates due to aging and spinal cord injury. Training for the recovery of proprioception is required because of the ADL and prevention of overturning. We have developed a new rehabilitation support system for “sensory training”. The purpose of this study is to perform clinical trials with 2 patients by using our system and discuss the results of clinical trials by analyzing the experimental data. In our system, video games are prepared as test programs for the proposed system. The measurements are performed one time before the operation and once or more until subjects are discharged from the hospital after the operation. In experiments, as the comparison studies, conventional quantitative evaluation tests, namely gravicorder test and 10 meter walking test are performed. As a result, this system plays a role of helping the patient with deteriorated proprioception to control lower limb as useful training tool based on the vision information feedback.

Proprioceptive change impairs balance control in older patients with low back pain

[Purpose] This study aims to determine the specific proprioceptive control strategy used during postural balance in older patients with low back pain (LBP) and non-LBP (NLBP) and to assess whether this strategy is related to proprioceptive decline and LBP. [Subjects and Methods] Pressure displacement center was determined in 47 older persons with LBP and 64 older persons with NLBP during upright stance on a balance board without vision. Gastrocnemius (GS) and lumbar multifidus muscle (LM) vibratory stimulations of 60 and 240-Hz, respectively, were applied to evaluate the relative contributions of different proprioceptive signals (relative proprioceptive weighting ratio, RPW) used in postural control. Age, height, weight, back muscle strength, L1/2 and L4/5 lumbar multifidus cross section area ratio, skeletal muscle mass index, sagittal vertical axis, and Roland-Morris disability questionnaire (RDQ) were evaluated. [Results] Compared with older patients with NLBP, those with LBP showed a lower RPW 240-Hz, lower L4/5 lumbar multifidus cross-sectional area ratio, and a significantly higher age and RDQ. Logistic regression analysis showed that RPW 240-Hz and age were independently associated with LBP, after controlling for confounding factors. [Conclusion] Older patients with LBP decreased their reliance on GS (RPW 240-Hz) proprioceptive signals during balance control.

Development of Measurement System for Quantitative Evaluation of Skillfulness of Lower Extremities

The final goal of our research is to develop a measurement system for quantitative evaluation of the skillfulness of the lower extremities. In our previous work, we developed the measurement system of the foot movement on the floor with the sitting posture. In this study, we developed a quantitative evaluation method of the skillfulness of the lower extremities. We verified the reliability of the proposed quantitative evaluation method by calculating the intra-rater reliability for two trials ICC(1,1) of the evaluation results.

A newly developed system for quantitative evaluation on hand sensorimotor integration function

This paper presents a newly developed quantitative evaluation system on hand sensorimotor integration function. The objective assessment of hand sensorimotor integration function should be necessary to evaluate how the affected thumb or fingers move smoothly. Our present study aims to construct the quantitative evaluation system of sensorimotor integration function of the hand finger. The experimental results show the different tendency between non-dominant hand and dominant hand in the healthy persons. Furthermore, the phenomenon that the visual information and the somatosensory information are integrated by the integration function, is found only for the healthy dominant hand.