Tasuku Miyoshi

Effect of the walking speed to the lower limb joint angular displacements, joint moments and ground reaction forces during walking in water.

Purpose: The purpose of this study was to compare the changes in ground reaction forces (GRF), joint angular displacements (JAD), joint moments (JM) and electromyographic (EMG) activities that occur during walking at various speeds in water and on land. Method: Fifteen healthy adults participated in this study. In the water experiments, the water depth was adjusted so that body weight was reduced by 80%. A video-motion analysis system and waterproof force platform was used to obtain kinematics and kinetics data and to calculate the JMs. Results: Results revealed that (1) the anterior-posterior GRF patterns differed between walking in water and walking on land, whereas the medio-lateral GRF patterns were similar, (2) the JAD patterns of the hip and ankle were similar between water- and land-walking, whereas the range of motion at the knee joint was lower in water than on land, (3) the JMs in all three joints were lower in water than on land throughout the stance phase, and (4) the hip joint extension moment and hip extensor muscle EMG activity were increased as walking speed increase during walking in water. Conclusions: Rehabilitative water-walking exercise could be designed to incorporate large-muscle activities, especially of the lower-limb extensor muscles, through full joint range of motion and minimization of joint moments.

Effects of loading and unloading of lower limb joints on the soleus H-reflex in standing humans

OBJECTIVE To investigate the effects of loading and unloading of the lower limb joints on the soleus H-reflex in standing humans. METHODS H-reflexes were elicited in the soleus muscle in subjects standing on a force platform in a water tank under the following loading conditions of the ankle and knee joints: control condition; reduced loads of -10 and -20 N; imposed loads of 10 and 20 N. The joint loading was altered by changing the combinations of buoys and weights attached to the lower limb segments, while total body weight was kept constant. RESULTS As the ankle- or knee-joint load was reduced, the H-reflex was significantly enhanced compared to that under the control condition. In contrast, the H-reflex was decreased as the ankle- or knee-joint load was increased. In both cases, similar levels of background activity were recorded. CONCLUSIONS The present results suggest that joint afferents might mediate the suppression of the soleus H-reflex in standing humans. However, the identification of the receptors and/or the mechanisms cannot be addressed under the current experimental set up. SIGNIFICANCE The results of this study give some basic insights into reflex control in an upright posture.

Inhibition of the human soleus Hoffman reflex during standing without descending commands

The purpose of the present study was to ascertain the contribution of peripheral sensory inputs to posture-related Hoffman reflex (H-reflex) modulation in the human soleus muscle. The soleus H-reflexes were elicited in the sitting (SI) and passive standing (ST) conditions in patients with clinically complete spinal cord injuries (SCI) and in neurologically normal subjects. The results clearly showed suppression of the H-reflex amplitude during the ST compared with the SI condition especially in the SCI group. Considering the lack of a descending neural command in the SCI patients, our findings suggest that peripheral sensory inputs primarily contribute to the reduction of the soleus H-reflex during the upright standing posture.

Lower limb joint moment during walking in water.

Purpose: Walking in water is a widely used rehabilitation method for patients with orthopedic disorders or arthritis, based on the belief that the reduction of weight in water makes it a safer medium and prevents secondary injuries of the lower-limb joints. To our knowledge, however, no experimental data on lower-limb joint moment during walking in water is available. The aim of this study was to quantify the joint moments of the ankle, knee, and hip during walking in water in comparison with those on land. Method: Eight healthy volunteers walked on land and in water at a speed comfortable for them. A video-motion analysis system and waterproof force platform were used to obtain kinematic data and to calculate the joint moments. Results: The hip joint moment was shown to be an extension moment almost throughout the stance phase during walking in water, while it changed from an extension- to flexion-direction during walking on land. The knee joint moment had two extension peaks during walking on land, whereas it had only one extension peak, a late one, during walking in water. The ankle joint moment during walking in water was considerably reduced but in the same direction, plantarflexion, as that during walking on land. Conclusions: The joint moments of the hip, knee, and ankle were not merely reduced during walking in water; rather, inter-joint coordination was totally changed.

Robotic gait trainer in water: Development of an underwater gait-training orthosis

Purpose. To develop a robotic gait trainer that can be used in water (RGTW) and achieve repetitive physiological gait patterns to improve the movement dysfunctions. Method. The RGTW is a hip-knee-ankle-foot orthosis with pneumatic actuators; the control software was developed on the basis of the angular motions of the hip and knee joint of a healthy subject as he walked in water. Three-dimensional motions and electromyographic (EMG) activities were recorded in nine healthy subjects to evaluate the efficacy of using the RGTW while walking on a treadmill in water. Results. The device could preserve the angular displacement patterns of the hip and knee and foot trajectories under all experimental conditions. The tibialis anterior EMG activities in the late swing phase and the biceps femoris throughout the stance phase were reduced whose joint torques were assisted by the RGTW while walking on a treadmill in water. Conclusion. Using the RGTW could expect not only the effect of the hydrotherapy but also the standard treadmill gait training, in particular, and may be particularly effective for treating individuals with hip joint movement dysfunction.

Automatic detection method of muscle fiber movement as revealed by ultrasound images

The objective of this study was to develop a method of muscle structure measurement based on the automatic analysis of muscle fibers, proximal fascias, and distal aponeurosis movements as revealed by a time-series of ultrasound images. This method was designed to detect changes in the length of muscle fiber movements, and its validity was demonstrated in a time-series of muscle movement, slow ankle dorsiflexion (10 degrees/s), by comparison to manual measurement. The results showed that, when this method was used, the changes in the length of the muscle fiber under slow muscle movement were smaller than those in manual operations by novice individuals. However, with the proposed method, it was possible to obtain a sufficient degree of validity and reliability for the changes in the length of the muscle fiber length compared with those in manual operations, since the correlation coefficients exceeded 0.8 which was tested by the linear regression. The proposed method suggests that automation reduces the errors caused by manual operations and makes the processing of data possible in an acceptable amount of time.

Development of body weight support gait training system using antagonistic bi-articular muscle model

The purpose of this study is to develop a body weight support gait training system for stroke and spinal cord injury. This system consists of a powered orthosis, treadmill and equipment of body weight support. Attachment of the powered orthosis is able to fit subject who has difference of body size. This powered orthosis is driven by pneumatic McKibben actuator. Actuators are arranged as pair of antagonistic bi-articular muscle model and two pairs of antagonistic mono-articular muscle model like human musculoskeletal system. Part of the equipment of body weight support suspend subject by wire harness, and body weight of subject is supported continuously by counter weight. The powered orthosis is attached equipment of body weight support by parallel linkage, and movement of the powered orthosis is limited at sagittal plane. Weight of the powered orthosis is compensated by parallel linkage with gas-spring. In this study, we developed system that has orthosis powered by pneumatic McKibben actuators and equipment of body weight support. We report detail of our developed body weight support gait training system.

Basic experiments of upper limb rehabilitation using haptic device system

Rehabilitation exercises which maintain a patients interest and quantitative evaluation of rehabilitation are required. To solve these problems, we have developed a haptic device system. This system consists of a haptic device, a display, a computer, and software for a training program. When users move the grip, the haptic device provides a virtual force, either assisting the movement of their arm or working against it. To investigate the functional effect of this system using a training program, we measured the grip position, velocity, force on the grip, and electromyographic (EMG) activities during a reaching task for five healthy subjects. Spatio-temporal patterns of both the velocity and grip force, the accuracy of the grip trajectories, and the EMG patterns were similar in all subjects. These results suggested that the EMG activities were improved by applying the virtual force to the grip. These results can be used for the development of rehabilitation training programs and evaluation methods.

2-D direction histogram based entropic thresholding

Abstract Local image features are effective descriptors for image analysis and are also important cues for image segmentation. In this paper, we propose a novel entropic thresholding approach. This approach incorporates local features into a conventional entropic method to implement the thresholding. The local features are obtained from an orientation histogram to describe the edge property of the local neighborhood. To verify the performance of our method, thresholding was carried out on different types of images and compared with some well-known entropic approaches. Experimental results show that using the local edge property can give a better thresholding result.

Development of Pneumatic Gait Assist System

The aim of this study is to develop a pneumatic gait training system. This study report the prototype of pneumatic gait training system based on a modified long-leg orthosis and a treadmill system. The special pneumatic actuator, the similar actuator to human muscular system, was used as the actuator for hip and knee flexion/extension movement. This prototype system of pneumatic gait training is able to utilize for both land and underwater environments. We evaluated this system by the experimental test on land and underwater conditions. It is indicated from the experiment test that 1) the hip and knee joint movement patterns of both on land and underwater gait were quite similar kinematics for normal gait pattern, 2) the activity of lower limb muscles decreased across the gait cycle on land gait, 3) the activity of hip extensor and knee flexor muscles decreased during stance phase in underwater gait. These results of this study suggest that the pneumatic gait training system might be effective for gait training to several motor disorders.