Electromyography-signal-based muscle fatigue assessment for knee rehabilitation monitoring systems

Kim, Hyeonseok,Lee, Jongho,Kim, Jaehyo Springer-Verlag 2018 Biomedical Engineering Letters (BMEL) Vol.8 No.4

A Smart Bench Press Machine: Automatic Weight Control Sensitive to User Tiredness

Kim, Jihun,Jo, Han-jin,Kim, Kiyoung,Ji, Hae-geun,Kim, Jaehyo The International Promotion Agency of Culture Tech 2019 International Journal of Advanced Culture Technolo Vol.7 No.1

In order to provide a safe free-weight-training environment to people without workout trainers, we suggest a smart bench press machine with an automatic weight control system sensitive to user tiredness. Physical weight plates on the machine are replaced with a hydraulic cylinder as a press load and the cylinder knob is coupled with a step motor to change its tensile force automatically in-between lifting exercises. Three subjects participated to verify the usability of the smart bench press machine. They were asked to lift a 6-RM press load 10 times with 3 different lifting conditions: 1) no assistance, 2) a human assistance, and 3) the automatic weight control. All subjects were not able to complete the 10 sets without assistance due to tiredness, but they finished the full sets under the two assistive conditions. Average lifting speeds under the automatic weight control condition showed the most consistent level. Normalized quasi-tension data based on surface electromyogram signals of both Pectoralis Majors revealed that the subjects maintained the target muscle activation level above 50% but not more than 80% throughout the 10 sets. Therefore, the smart bench press machine is expected to both keep pace with the lifting exercise and reduce risk of injuries due to excessive muscle tensions.

Human Arm Posture Control Using the Impedance Controllability of the Musculo-Skeletal System Against the Alteration of the Environments

Jaehyo Kim,Makoto Sato,Yasuharu Koike 제어·로봇·시스템학회 2002 International Journal of Control, Automation, and Vol.4 No.1

We show that humans execute the postural control ingeniously by regulating the impedance properties of the musculo-skeletal system as the motor command against the alteration of the environment. Adjusting muscle activity can control the impedance properties of the musculo-skeletal system. To quantify the changes in human arm viscoelasticity on the vertical plane during interac-tion with the environment, we asked our subject to hold an object. By utilizing surface electromyographic(EMG) studies, we deter-mined a relationship between the perturbation and a time-varying muscle co-activation. Our study showed when the subject lifts the object by himself the muscle stiffness increases while the torque remains the same just before the lift-off. These results suggest that the central nervous system(CNS) simultaneously controls not only the equilibrium point(EP) and the torque, but also the muscle stiffness as themotor command in posture control during the contact task.

전통적인 길이 척도 환산에 대한 역사 · 문화적 재고

김재효(Kim JaeHyo),강연석(Kang YeonSeok),고호경(Ko HoKyoung) 한국의사학회 2010 한국의사학회지 Vol.23 No.2

Currently, in Korea, all lengths are written in “meter” unit, and the non-statutory measuring units are banned for use. However, in some fields, traditional measuring units are widely used with necessary modifications, and people in such fields raise varying arguments on conversion to “meter” unit. This research examines traditional measuring units from historical and cultural viewpoints, and provides suggestions on how to improve consistency and standardization for more accurate and effective exchange of scientific opinions.

Muscle Synergy Analysis for Stroke During Two Degrees of Freedom Reaching Task on Horizontal Plane

Hyeonseok Kim,Jongho Lee,Jaehyo Kim 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.2

This study aimed to investigate muscle synergies from major muscles that contribute to each degree of freedom (DOF) in a low DOF task with trunk restraint during a fundamental reaching task used frequently in daily life. Seven non-patients (controls) and eleven stroke patients (mild or severe groups) in Brunnstrom stage 2–4 recovery were assessed. Subjects performed two DOF reaching tasks requiring motor coordination of the elbow and shoulder on the horizontal plane. Electromyography signals were measured during the task, and muscle synergy data extracted from them were analyzed using cluster analysis. No significant differences were noted between patients with stroke and healthy subjects in terms of the coefficient of determination, R-squared, determined according to the number of modules. Cluster analysis revealed that each of the clusters in the control and mild groups was governed by one channel. However, one cluster in the severe group was governed by two channels. When the clusters of the mild group and the control group were compared, the highest similarities (all values exceeded 0.9) were noted between the corresponding clusters of the two groups. All other similarity values were < 0.8. A similar trend was noted when the severe group clusters were compared with control group clusters; however, only three corresponding pairs of clusters exhibited similarity values exceeding 0.9, while the rest were < 0.8. Muscle synergies during the two DOF reaching tasks with trunk restraint showed differences in extensors between healthy individuals and patients with stroke.

A Wearable Soft Robot for Stroke Patients’ Finger Occupational Therapy and Quantitative Measures on the Joint Paralysis

Jihun Kim,Geonhui Lee,Hanjin Jo,Wookhyun Park,Yu Shin Jin,Ho Dong Kim,Jaehyo Kim 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.12

We suggest a wearable soft robot for post-stroke, hemiplegic patients’ finger rehabilitation and quantitative evaluations on the joint paralysis. The device consists of a pair of gloves. One measures finger positions of the normal side, and the other induces symmetric movements on the affected side by pneumatic force. Ten patients at Brunnstrom stage 3 and 4 from a local hospital participated in this study. They performed Rolyan Stacking Cones 10 times with and without the support of the soft robot. We measured subjects’ proximal interphalangeal angles and air pressures in the pneumatic glove during the exercise to monitor grab/release patterns. The soft robot helped open their paralyzed finger joints by more than 50 degrees on average regardless of Brunnstrom stages. We applied pattern recognition methods on the measurement to quantitatively evaluate the subjects. A support vector machine revealed a misclassification rate of 20%, implying that there were a considerable number of overlapping data sets near the boundary between Brunnstrom stages. K-means method with three clusters suggested a new subject group near the support vector machine border. Thus, we conclude that our wearable soft robot not only provides grab/release guides to post-stroke patients but also provides quantitative information on their finger paralysis supplementary to the existing qualitative assessments.

A Smart Bench Press Machine : Automatic Weight Control Sensitive to User Tiredness

Jihun Kim,Han-jin Jo,Kiyoung Kim,Hae-geun Ji,Jaehyo Kim 국제문화기술진흥원 2019 International Journal of Advanced Culture Technolo Vol.7 No.1

In order to provide a safe free-weight-training environment to people without workout trainers, we suggest a smart bench press machine with an automatic weight control system sensitive to user tiredness. Physical weight plates on the machine are replaced with a hydraulic cylinder as a press load and the cylinder knob is coupled with a step motor to change its tensile force automatically in-between lifting exercises. Three subjects participated to verify the usability of the smart bench press machine. They were asked to lift a 6-RM press load 10 times with 3 different lifting conditions: 1) no assistance, 2) a human assistance, and 3) the automatic weight control. All subjects were not able to complete the 10 sets without assistance due to tiredness, but they finished the full sets under the two assistive conditions. Average lifting speeds under the automatic weight control condition showed the most consistent level. Normalized quasi-tension data based on surface electromyogram signals of both Pectoralis Majors revealed that the subjects maintained the target muscle activation level above 50% but not more than 80% throughout the 10 sets. Therefore, the smart bench press machine is expected to both keep pace with the lifting exercise and reduce risk of injuries due to excessive muscle tensions.

저 레이놀즈 수가 원심압축기 성능에 미치는 영향

김재효(Jaehyo Kim),정영진(Young-Jin Jung),최민석(Minsuk Choi) 한국유체기계학회 2015 한국유체기계학회 학술대회 논문집 Vol.2015 No.12

한국 HCI 학회논문지 손 재활 운동을 위한 생체신호 및 3D 인터페이스기반 가상물체 이동 프로그램

김진욱(Jinuk Kim),권지혜(Jihye Kwon),임수빈(Subin Im),이성윤(Sungyoon Lee),김재효(Jaehyo Kim) 한국HCI학회 2014 한국HCI학회 학술대회 Vol.2014 No.2

본 논문에서는 손에 부착한 Attitude & Heading Reference System(AHRS)과 근전도 전극을 통해 추출한 근육의 활성도를 이용하여 손 마비 환자를 위한 재활 프로그램을 제안한다. 제안하는 프로그램은 기존 기계적 장치에 의존하던 재활 프로그램에서 벗어나 디지털 미디어를 이용하여 환자 스스로 재활할 수 있을 뿐 아니라, 근전도의 강도에 따라 부하가 있는 환경에서 또한 재활이 가능하다. 본 논문에서는 제안한 인터페이스의 구조와 형태, 구현을 제시하며, MATLAB 기반으로 구현한 간단한 실험을 통해 인터페이스의 활용 가능성을 평가하였다. The paper proposes a rehabilitation program for hand-paralyzed patients using Attitude & Heading Reference System (AHRS) and muscle signal activity from the patient’s electromyogram. Unlike current rehabilitation programs using mechanical devices, this program not only helps the patients practice rehabilitation themselves using digital media, but also reflects the magnitude of the force under overloaded environment according to the stiffness of the muscle signal. The paper suggests the structure, shape, and realization of the program and evaluates the practicality of the MATLAB based program through simple applications and experiments.

Dual Mode Feedback-Controlled Cycling System for Upper Limb Rehabilitation of Children with Cerebral Palsy

Cho, Seung-Yeon,Kim, Jihun,Seo, Seong-Won,Kim, Sung-Gyung,Kim, Jaehyo The International Promotion Agency of Culture Tech 2019 International Journal of Advanced Culture Technolo Vol.7 No.1

Background/Objectives: This paper proposes a dual mode feedback-controlled cycling system for children with spastic cerebral palsy to rehabilitate upper extremities. Repetitive upper limb exercise in this therapy aims to both reduce and analyze the abnormal torque patterns of arm movements in three- dimensional space. Methods/Statistical analysis: We designed an exercycle robot which consists of a BLDC motor, a torque sensor, a bevel gear and bearings. Mechanical structures are customized for children of age between 7~13 years old and induces reaching and pulling task in a symmetric circulation. The shafts and external frames were designed and printed using 3D printer. While the child performs active/passive exercise, angular position, angular velocity, and relative torque of the pedal shaft are measured and displayed in real time. Findings: Experiment was designed to observe the features of a cerebral palsy child's exercise. Two children with bilateral spastic cerebral palsy participated in the experiment and conducted an active exercise at normal speed for 3 sets, 15 seconds for each. As the pedal reached 90 degrees and 270 degrees, the subject showed minimum torque, in which the child showed difficulty in the pulling task of the cycle. The passive exercise assisted the child to maintain a relatively constant torque while visually observing the movement patterns. Using two types of exercise enabled the child to overcome the abnormal torque measured in the active data by performing the passive exercise. Thus, this system has advantage not only in allowing the child to perform the difficult task, which may contribute in improving the muscle strength and endurance and reducing the spasticity but also provide customizable system according to the child's motion characteristic. Improvements/Applications: Further study is needed to observe how passive exercise influences the movement characteristics of an active motion and how customized experiment settings can optimize the effect of pediatric rehabilitation for spastic cerebral palsy.