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Pohang, South Korea

Hong J.-S.,Gerontechnology center | Kim J.-H.,Gerontechnology center | Hong J.-H.,Korea University | Chun K.-J.,Gerontechnology center
Journal of Biomechanical Science and Engineering | Year: 2012

This study aimed to analyze the muscular activity associated with the proper function, stability, and mobility of the shoulder joint. In the field of orthopedics, the shoulder joint is recognized as having extensive mobility. Using an electromyograph (sEMG), the muscular activity in 10 elderly male subjects was analyzed during joint movements while performing isokinetic exercises. The muscular activity of an agonist was analyzed using both the percent maximum voluntary contraction (%MVC) and the EMG (μV) value before normalization. The %MVC quantified four motions (flexion, extension, abduction, and adduction) for the 10 upper limb muscles whereas the latter did not. The results showed that the pectoralis major (clavicular insertion) activated as an agonist during abduction and adduction. A comparison of when the muscles activated based on each motion revealed that the middle deltoid muscle activated the fastest during abduction. This research is expected to facilitate measurement of the shoulder function for both rehabilitation equipment and their associated programs. © 2012 by JSME. Source

Kim J.H.,Gerontechnology center | Chun K.J.,Gerontechnology center | Hong J.S.,Korea University | Kim C.W.,Gerontechnology center | Hong J.H.,Korea University
ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) | Year: 2012

The hemiparalysis, which is a widely known side effect of the disease, requires consistent and accurate rehabilitation exercise treatment. The Grahamizer is a representative piece of equipment for such treatment. Because it consists of a double pivot system, under exercise, the irregularly moving pivots could create an unintended movement and malfunction. Using the Grahamizer, this study analyzed movement patterns based on changes in the armrest's length and the central axis location for a stable and accurate upper limb rehabilitation exercise. Eight healthy subjects participated in the study. The Grahamizer, which allows the length of the armrest and the central axis location to be adjusted, was used for experimental equipment. The length could be adjusted to five levels (280mm, 220mm, 160mm, 100mm, and 40mm), and the location ranged from 5 levels to 1 level based on the length of the arm support (280mm: 5positions, 220mm: 4positions, 160mm: 3positions, 100mm: 2positions, 40mm: 1position). A marker located above a knob traced the knob's movements. The experiment was conducted three times. Each subject held the knob and implemented rotational movements passively, with an angular velocity of 30°/s. After integrating the subjects' movement traces, the tendency was analyzed. A previous study provided an analysis of the elbow and shoulder joint movements under a normal upper-body rotation movement. This study on movement traces was conducted based on those results. Longer armrest lengths and greater distances between the central axis location and knob showed greater stability for the rotation movements. Remarkable results were found for changes in the axis location. However, smaller distances between the axis location and knob revealed larger movement traces. A previous study found, when a counterclockwise rotation was defined as 0°∼360°, that an elbow motion of 0°∼180° is flexion and 180°∼360° is extension. The shoulder joint motions are similar: 0°∼90°: medial rotation, 90°∼180°: lateral rotation, 180°∼270° medial rotation, and 270°∼360°: lateral rotation. According to the previous study, with a larger trace (smaller distance between the axis location and knob), the rotation movements of the elbow and shoulder are more accurate from 0° to 180° than from 180° to 360°. The experiment confirmed that the Grahamizer's armrest axis location has an impact on movement traces, and changes in the traces prevented the intended joint exercise. Under the circumstances, the location is an important design variable when developing the Grahamizer. Copyright © 2012 by ASME. Source

Hong J.S.,Korea University | Chun K.J.,Gerontechnology center | Kim J.H.,Gerontechnology center | Hong J.H.,Korea University
ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) | Year: 2012

An increase in the aging population around the world and in degenerative diseases has caused an epidemic of stroke. Hence, rehab equipment for treating its after-effects has been actively developed. A repeated upper-body rehab exercise is required and this exercise can only yield good results when its accurate motion is guided by a therapist. However, few kinematics studies have been conducted based on design variables such as changes in the rotational central axis and body measurement. So, this study analyzed the angular changes in two motions of the elbow (Flexion-Extension: F-E, Pronation- Supination: P-S) and three motions of the scapula (Anterior- Posterior tilt: A-P, Internal-External rotation: I-E, Upward- Downward rotation: U-D) based on changes in the arm support length and central axis location. Eight healthy subjects participated in this study. Rehabilitation equipment for the upper limb, which can be adjusted to different arm support lengths and central axis locations, was used as the experimental equipment. The length could be adjusted to five levels (280 mm, 220 mm, 160 mm, 100 mm, and 40 mm). In the case of an experiment involving changes in the axis locations, the length was fixed as 280 mm, which allowed five different axis locations. Each subject implemented a rotational movement passively at an angular velocity of 30°/s. In this study, we observed changes in the motion patterns of the upper-limb rotational movement based on the length and the location. The patterns based on the two design variables revealed a consistent tendency under the elbow (forearm) and the scapula (shoulder rhythm). Yet, three scapula motions showed little changes in the angular width, and only I-E showed an angular width of 5°. First, with respect to the tendency of the five motions based on changes in the lengths, the prolonged length showed a decreased angular width. Second, in terms of the tendency of the five motions based on changes in the locations, a relatively long distance between the handle and the axis (Location 1 → Location 5) confirmed a decreased angular width owing to a relatively small rotational movement at Location 5. The F-E motion of the elbow clearly showed two time cycles per rotation. Other motions revealed one time cycle per rotation. With respect to the upper-body rotational movement, we confirmed that motions related to the forearm were more active than motions related to the shoulder. Copyright © 2012 by ASME. Source

Hong J.-S.,Gerontechnology center | Hong J.-S.,Korea University | Chun K.-J.,Gerontechnology center | Kim J.-H.,Gerontechnology center | And 2 more authors.
International Journal of Precision Engineering and Manufacturing | Year: 2013

This study examined muscle imbalance in the cases of isokinetic movement of the shoulder joint, targeting the young and the old. The experiment was divided into the dominant and non-dominant sides and consisted of flexion, extension, abduction, adduction, external rotation, and internal rotation. Regarding the angular velocity, the peak torque was measured for the equal condition of 30, 60, and 120 deg/s. The concentric and eccentric muscular strengths were measured based on each motion. This study showed that concentric movement tended to decrease the peak torque on the dominant and non-dominant sides alike by increasing the angular velocity, whereas an eccentric movement had a tendency to boost the peak torque by increasing the velocity except for the dominant external rotation. In the case of the young, most of the motion showed that the dominant side had a higher peak torque than the non-dominant side regardless of the angular velocity. The results from the elderly were different from the young, and the non-dominant side tended to have a higher peak torque than the dominant one regardless of the angular velocity. According to the Antagonistic Strength relationships(Concentric) in the young and the old, young people's flexion/ extension ratio was 3 ~ 13%, abduction/adduction 1 ~ 16%, and external rotation/internal rotation 5 ~ 10%. The data from the elderly showed that the ratio of abduction/adduction under concentric contraction ranged from 20 to 31%, which was higher than that reported previously. The elderly showed an imbalanced muscle tendency. This result is expected to provide a useful basic guideline for measuring the shoulder function of the young and old, and consisted rehabilitation equipment and its programs. © 2013 Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg. Source

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