Lifestyle and Health/Medicine

Tadayoshi Asaka

Contributing to Rehabilitation of Balance Disability

Tadayoshi Asaka , Professor

Faculty of Health Sciences (Departments of Health Sciences, School of Medicine)

High school : Hokkaido Kitami Hokuto High School

Academic background : College of Medical Technology (Now: Department of Health Sciences), Hokkaido University

Research areas
Research keywords
Postural control, motor control, rehabilitation

What started you on your current path of research?

Picture 1: Testing in the motor control laboratory (Pennsylvania State University). This experience became the basis of my current research.

After graduating from the Department of Engineering, I entered the medical field because of my interest in people. Afterwards, I learned a great deal from patients with disabilities while gaining clinical experience as a physical therapist. Because the hospital where I worked had many patients with intractable nerve and muscle disorders (Parkinson's disease, spinocerebellar degeneration, etc.), I became interested in postural balance (postural control), which is the essential element of basic movements like standing and walking.
My current research method is based on my studies in America (Picture 1), where I received direct instruction from a professor who is a leader in the field of motor control. The motor control theories, analytical methods, and other approaches promoted by the professor have been a great asset in the advancement of my current research. By clarifying the mechanism of postural control, I hope to contribute to rehabilitation for improved balance, prevention of falls in the elderly, and other areas.


What are you researching?

Picture 2: Studying muscle activities in the body and legs immediately before the release of a bar held with both hands (connected to the weight behind).

Before we move, the muscles that regulate posture receive a pre-programmed signal from the brain to maintain posture after moving. At the same time, the brain picks up sensory signals (visual sensation, labyrinthine sensory, somatosensory) caused by bodily movement, and uses them to regulate and maintain balance after moving. Focusing on the former signaling system, known as anticipatory postural control (Picture 2), and the latter system, known as responsive control (Picture 3), we are investigating the effects on them of aging by comparing young people and older people and by studying characteristic patterns in patients with balance disorders (cerebrovascular disease, Parkinson's disease, cerebellar ataxia, etc.). We are also working with sport science researchers to study the outstanding posture control of elite athletes.

Picture 3: Researching postural response induced by horizontal back-and-forth movement of the floor surface in an elite ski jumper

The muscle activities in posture-related muscles are measured with an electromyograph (Picture 4). Wireless telemeter electrodes are attached to the body, and the action potential created by muscle contraction is detected by a receiver. Postural changes and the body’s center of gravity are calculated using a three-dimensional movement analysis system (Picture 5). Multiple markers are attached to specific areas of the body and infrared cameras compute spatial coordinates. Force-plates are also used to measure pressure at the soles of the feet and can detect minute changes in postural control.


Picture 4: Electromyograph system
Simultaneously measures multiple muscle activities: The inset shows the wireless telemeter while the antennae in the center of the photo are the receivers.

Picture 5: Three-dimensional movement analysis systemThe body’s center of gravity and the angle of the joints are computed from the spatial coordinates of multiple markers: The spots on the arms and legs are the markers while the black flooring is the force-plate



What's next?

Figure  Example of a motor learning test
The objective is to match the center of pressure calculated by the force plate with the target (green dot) moving back and forth across the monitor. When the center of pressure enters the forward or backward target area (dotted lines), feedback is given by either visual (red dots) or auditory stimuli.

Clinical rehabilitation generally involves movement training through sensory feedback based on sight, hearing, and somatic sensation. For balance training likewise, I hope to devise an effective motor-learning method based on sensory feedback. The picture on the right is one example: The center of pressure is calculated by the force-plate and displayed on the monitor in real-time. In learning to balance by moving the center of gravity backwards and forwards, we are studying the difference in learning effect between visual and auditory feedbacks.
By expanding the scope of joint research, both in interdisciplinary and international terms, my objective is to clarify movement and postural control mechanisms in patients with nervous system diseases so as to develop effective learning methods and thereby contribute to the development of neurophysiotherapy.