• 대한인간공학회지
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• 제30권6호
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• pp.689-694
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• 2011

Objective: The aim of this study is to evaluate the fluctuation of signal amplitude during repetitive dynamic contraction based on surface electromyography(EMG). Background: The most previous studies were considered isometric muscle contraction and they were difference to smoothing window length by moving average filter. In practical, the human movement is dynamic state. Dynamic EMG signal which indicated as the nonstationary pattern should be analyzed differently compared with the static EMG signal. Method: Ten male subjects participated in this experiment, and EMG signal was recorded by biceps brachii, anterior/posterior deltoid, and upper/lower trapezius muscles. The subject was performed to repetitive right horizontal lifting task during ten cycles. This study was considered three independent variables(muscle, amplitude processing technique, and smoothing window length) as the within-subject experimental design. This study was estimated muscular activation by means of the linear envelope technique(LE). The dependent variable was set coefficient of variation(CV) of LE for each cycle. Results: The ANOVA results showed that the main and interaction effects between the amplitude processing technique and smoothing window length were significant difference. The CV value of peak LE was higher than mean LE. According to increase the smoothing window length, this study shows that the CV trend of peak LE was decreased. However, the CV of mean LE was analyzed constant fluctuation trend regardless of the smoothing window length. Conclusion: Based on these results, we expected that using the mean LE and 300ms window length increased reproducibility and signal noise ratio during repetitive dynamic muscle contraction. Application: These results can be used to provide fundamental information for repetitive dynamic EMG signal processing.

• 한국융합학회논문지
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• 제10권3호
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• pp.67-72
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• 2019

본 연구는 일주일 동안의 컴퓨터 사용시간이 몸통 근육 두께와 압력 통증 역치에 미치는 영향을 분석하였다. 33명의 대상자를 일주일에 컴퓨터를 10시간 이하(A 그룹), 10시간에서 20시간(B 그룹), 20시간 이상 사용하는 그룹(C 그룹)으로 나누어 위 등세모근, 작은가슴근, 앞 목갈비근, 중간 목갈비근의 근 두께와 위 등세모근, 작은가슴근, 앞 목갈비근, 중간 목갈비근, 어깨올림근의 압력 통증 역치를 측정하였다. 본 연구의 결과 C 그룹의 작은가슴근, 앞 목갈비근, 중간 목갈비근은 다른 그룹들의 근 두께에 비해 유의하게 증가되었고(p<.05) 위 등세모근, 앞 목갈비근, 작은가슴근, 어깨올림근의 압력통증역치는 다른 그룹들에 비해 유의하게 감소하였다(p<.05). 그러므로, 본 연구는 1주일 동안 컴퓨터를 장시간 사용하는 사람들은 장시간 컴퓨터 사용이 다양한 근골격계 질환의 원인이 될 수 있음을 인지하고 그에 따른 적절한 예방적 접근을 수행할 것을 권장한다.

• 한국전문물리치료학회지
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• 제16권2호
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• pp.67-76
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• 2009

In order to prevent upper extremity musculoskeletal disorders, effective keyboard selection is an important consideration. The aim of this study was to compare upper extremity muscle activity according to transverse plane angle changes during vertical keyboard typing. Sixteen healthy men were recruited. All subjects had a similar typing ability (rate of more than 300 keystrokes per minute) and biacromion and forearm-fingertip lengths. Four different types of keyboard (vertical keyboard with a transverse plane angle of $60^{\circ}$, $96^{\circ}$, or $120^{\circ}$, and a standard keyboard) were used with a wrist support. The test order was selected randomly for each subject. Surface electromyography (EMG) was used to measure upper extremity muscle activity during a keyboard typing task. The collected EMG data were normalized using the reference contraction and expressed as a percentage of the reference voluntary contraction (%RVC). In order to analyze the differences in EMG data, a repeated one-way analysis of variance, with a significance level of .05, was used. Bonferroni correction was used for multiple comparisons. There were significant differences in the EMG amplitude of all seven muscles (upper trapezius, middle deltoid, anterior deltoid, extensor carpi radialis, extensor carpi ulnaris, flexor carpi radialis, and flexor carpi ulnaris) assessed during the keyboard typing task. The mean activity of each muscle had a tendency to increase as the transverse plane angle increased. The mean activity recorded during all vertical keyboard typing was lower than that recorded during standard keyboard typing. There was no significant difference in accuracy and error scores; however, there was a significant difference between transverse plane angles of $60^{\circ}$ and $120^{\circ}$ with regard to comfort. In conclusion, a vertical keyboard with a transverse plane angle of $60^{\circ}$ would be effective in reducing muscle activity compared with vertical keyboards with other transverse plane angles.