• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1588-1593
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• 2008

This paper describes a real-time isometric pinch force prediction algorithm from surface electromyogram (sEMG) using multilayer perceptron (MLP) for human robot interactive applications. The activities of seven muscles which are observable from surface electrodes and also related to the movements of the thumb and index finger joints were recorded during pinch force experiments. For the successful implementation of the real-time prediction algorithm, an off-line analysis was performed using the recorded activities. Four muscles were selected for the force prediction by using the Fisher linear discriminant analysis among seven muscles, and the four muscle activities provided effective information for mapping sEMG to the pinch force. The MLP structure was designed to make training efficient and to avoid both under- and over-fitting problems. The pinch force prediction algorithm was tested on five volunteers and the results were evaluated using two criteria: normalized root mean squared error (NRMSE) and correlation (CORR). The training time for the subjects was only 2 min 29 sec, but the prediction results were successful with NRMSE = 0.112 ${\pm}$ 0.082 and CORR = 0.932 ${\pm}$ 0.058. These results imply that the proposed algorithm is useful to measure the produced pinch force without force sensors in real-time. The possible applications include controlling bionic finger robot systems to overcome finger paralysis or amputation.

• Journal of the Ergonomics Society of Korea
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• v.32 no.3
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• pp.273-278
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• 2013

Objective: This study aims to analyze and evaluate fatigue in upper trapezius muscles of adults when inputting text on a smart phone, thereby examining the risk of cumulative trauma disorders in the musculoskeletal system of the upper extremity. Method: Forty-five healthy adults were divided equally into three groups: a smartphone group, a notebook group, and a desktop group. A surface electromyogram was placed on the upper trapezius muscle of each participant, after which they inputted text for ten minutes within an ergonomic setting; their side posture was recorded on video and analyzed. Results: The spectral edge frequency values for the smartphone group, as recorded from the upper right trapezius muscles on the surface electromyogram, showed a significant decrease(p<.05). Regarding the RULA, all three groups had results indicating "action level 2". Conclusion: All three groups had results indicating "action level 2" according to the RULA, which means that additional research on the posture of the participants while performing tasks is necessary, and their posture needs to be corrected. In particular, the smartphone group has the highest levels of fatigue in the upper trapezius muscles, suggesting that the task of inputting text on a smartphone is a high risk for causing cumulative trauma disorders.

• Journal of Korean Physical Therapy Science
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• v.25 no.1
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• pp.20-30
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• 2018

Background: This study evaluates the effects of lower muscle activity of squat exercise on supporting surface and visual feedback. Methods: The subjects include 30 healthy subjects. To measure muscle activation of the lower limb during squat exercise(stable and unstable surface, visual and unvisual). For evaluation of muscle activation(rectus femoris, biceps femoris), was measured using the Electromyogram, EMG was used. Results: The results shows that Rectus Femoris(RF) and Biceps Femoris(BF) muscle activations were significantly (p<0.05) difference in unvisual-unstable surface(USUV), unvisual-stable surface(SUV), visual-unstable surface(USA), and visual-stable surface(SV) during squat exercise. Conclusion: Squat exercise can improve muscle activation of the lowe limb. particularly, unvisual-unstable surface during squat exercise can improve muscle activation of the lowe limb.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.19 no.2
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• pp.61-66
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• 2013

Background: This study tried to identify the bridge exercise posture for efficient exercise application by comparing muscle activity of buttocks and thighs according to internal-external rotation and pronation & supination in bridge exercise. Method: Nine males in their 20s living in D city were randomly selected as subjects. Muscles such as vastus medialis oblique (VMO), vastus lateralis (VL), semitendinosus (ST), biceps femoris (BF), gluteus maximus (GMAX), gluteus medius (GMED), tensor fasciae latae(TFL), and adductor longus (ADL) were measured using eight channel surface electromyogram (MyoSystem 1400A, Noraxon, USA) to measure muscle activity. Statistics process was performed through paired t test. Results: In the changes in electromyogram signals according to internal-external rotations according to internal-external rotation of shinbones, in most cases muscle activity was higher in external rotation than in internal rotation, but there was no statistical significance (p>.05). In particular, it was lower in TFL and ADL. There was no statistical significance in the comparison between two groups (p>.05). In the changes in electromyogram signals according to internal-external rotations according to pronation & supination of thighs, GMED showed significantly higher value in supination than in pronation (p>.05), and in ADL pronation is significantly higher than supination (p<.05). Conclusion: In internal-external rotation of shinbone and pronation & supination of thighs in bridge exercise, changes in muscle length can make effects on muscle activity of buttocks and thighs. Therefore, muscle strength enforcement program on buttocks and thighs through bridge exercise can make effects on patients with lower limb functional damages in clinical situations.

• Journal of the HCI Society of Korea
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• v.10 no.2
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• pp.21-26
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• 2015

NUI (Natural User Interface) system interprets the user's natural movement or the signals from human body to the machine. sEMG (surface electromyogram) can be observed when there is any effort in muscle even without actual movement, which is impossible with camera and accelerometer based NUI system. In sEMG based movement recognition system, the minimal number of electrodes is preferred to minimize the inconvenience. We analyzed the decrease in recognition accuracy as decreasing the number of electrodes. For the four kinds of movement intention without movement, extension (up), flexion (down), abduction (right), and adduction (left), the multilayer perceptron classifier was used with the features of RMS (Root Mean Square) from sEMG. The classification accuracy was 91.9% in four channels, 87.0% in three channels, and 78.9% in two channels. To increase the accuracy in two channels of sEMG, RMSs from previous time epoch (50-200 ms) were used in addition. With the RMSs from 150 ms, the accuracy was increased from 78.9% to 83.6%. The decrease in accuracy with minimal number of electrodes could be compensated partly by utilizing more features in previous RMSs.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.8
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• pp.132-141
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• 2009

In this paper, we describe finger force estimation from surface electromyogram (sEMG) data for intuitive and delicate force control of robotic devices such as exoskeletons and robotic prostheses. Four myoelectric sites on the skin were found to offer favorable sEMG recording conditions. An artificial neural network (ANN) was implemented to map the sEMG to the force, and its structure was optimized to avoid both under- and over-fitting problems. The resulting network was tested using recorded sEMG signals from the selected myoelectric sites of three subjects in real-time. In addition, we discussed performance of force estimation results related to the length of the muscles. This work may prove useful in relaying natural and delicate commands to artificial devices that may be attached to the human body or deployed remotely.

• PNF and Movement
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• v.10 no.4
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• pp.25-31
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• 2012

Purpose : The purpose of present study was to investigate the effects of proprioceptive neuromuscular facilitation (PNF) lifting on contralateral leg muscle activities in a seated position. Methods : Twenty healthy subjects were recruited for this study. Lifting was performed from each of the three position. An surface electromyogram (EMG) was used to record the EMG activities from vastus medialis (VM), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius medialis (GM) in contralateral leg muscle. The data were analyzed using a repeated measures of one-way analysis of variance (ANOVA) with post-hoc Bonferroni's correction to determine the statistical significance. Results : The results of this study were summarized as follows: In comparison to the start position, percentage maximal voluntary isometric contraction (%MVIC) values of the VM, TA and GM demonstrated a significantly higher activities in the end position(p<.05). Conclusion : The result shows that contralateral leg muscles activities significantly more increase in the end position when PNF lifting was applied. Therefore, this study will be used to prove effect of indirect approach for the stability and strengthening in patients with leg impairments.

• The Journal of Korean Physical Therapy
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• v.30 no.6
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• pp.211-217
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• 2018

Purpose: This study is to investigate influence of tDCS on lower limb muscle activity and balance ability in soccer player. Methods: Sessions were conducted with 15 subjects in tDCS group and 15 in action observation training group for 20 minutes, 5 sessions a week, for 8 weeks. All soccer players underwent 30 minutes of plyometric training before main exercise. To evaluate lower limb muscle activation, rectus femoris and biceps femoris were taken measure using surface electromyogram system and to evaluate balance ability, surface area, whole path length, limited of stability were measured using biorescue. Results: Regarding balance shown in surface area, whole path length, limited of stability and muscle activation in rectus femoris and biceps femoris, tDCS group showed more significant change than action bservation training group. Conclusion: Therefore, intervention using tDCS is more effective in improving lower limb muscle activation and balance ability than action observation training.

• Korean Journal of Applied Biomechanics
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• v.22 no.3
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• pp.349-356
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• 2012

This study aimed to assess the effects of progressive lumbar stability exercises and lumbar stability exercises on changes in the transversus abdominis muscle thickness and lower extremity muscle fatigue index in soccer players. Ten subjects were assigned to undergo training in each of the 2 groups, namely, the progressive lumbar stability exercise group and lumbar stability exercise group. Each intervention session lasted for 30 min, and 4 sessions were conducted in a week for 6 weeks for soccer players of S. University in Jeonnam, Korea. Changes in the transversus abdominis muscle thickness and lower extremity muscle fatigue index were measured using ultrasound and surface electromyogram. The results of the ultrasound measurement for the transversus abdominis muscle thickness indicated that progressive lumbar stability exercises were more effective than lumbar stability exercises. The results of the lower extremity muscle fatigue index measurements using surface electromyogram indicated that the fatigue index decreased in the progressive lumbar stability exercise group. Progressive lumbar stability exercise is believed to have put more workload during the shaking of the limbs, leading to increased stability and increased efficiency of the lower extremity muscle, thereby decreasing the fatigue index. Therefore, progressive lumbar stability exercises can be an effective measure for preventing injuries and improving the game performance of sports players by increasing the transversus abdominis muscle thickness and decreasing the lower extremity muscle fatigue index.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.1
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• pp.17-22
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• 2009

In this paper, we extract well-known parameters such as zero crossing rate(ZCR), low band energy(Band) and median frequency(MDF) from surface electromyogram (EMG), and compare to evaluate themselves as measures for fatigue. In experiments, 3 males and 3 females volunteered to participate in surface EMG recordings placed on the biceps brachii and each recording experiment continued until exhaustion.