• Journal of Oral Medicine and Pain
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• v.22 no.1
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• pp.145-155
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• 1997

The purpose of this study was to compare differences in endurance time and EMG power spectral characteristics of the masticatory muscles during sustained isometric contraction between patients and controls. 15 CMD patients{8 women and 7 men, aged 15 to 38 years(24.1$\pm$7.5)}, and 15 healthy volunteers{8 women and 7 men, aged 15 to 30 years(24.7$\pm$3.4)} without past history or present symptoms of CMD were included in this study. Sustained isometric contractions of masticatory muscles were perfomeed as long as possible at 50% level of maximum voluntary contraction(MVC) of EMG activity via visual feedback, and the duration of sustained isometric contraction(endurance time) was examined. The author perfomed EMG power spectral analysis in the myoelectric signals of masseter and anterior temporal muscle during sustained isometric contraction in CMD patients with chronic muscle pain and healthy controls. The author came to following conclusions from the results. 1. The endurance time of the patient group was shorter than the control group in sustained isometric contraction of masticatory muscles(p<0.01). 2. MF values of masticatory muscles with sustained isometric contraction during endurance time were decreased following regression line in both groups(p<0.01, r>0.9). 3. The amount of MF shift to lower frequency range exhibited no significant differences between the patients and the control group in sustained isometric contraction during endurance time. 4. SMF to lower frequency range of the patient group was steeper than the control group in sustained isometric contraction during endurance time(p<0.05).

• Journal of Oral Medicine and Pain
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• v.20 no.2
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• pp.269-281
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• 1995

To study the characteristics of EMG power spectrum of masticatory muscles during sustained isometric contraction and recovery at various contraction times, the author analysed the EMG signals of anterior temporal and masseter muscles before, during, and after sustained isometric contraction at 50% level of maximum voluntary contraction (MVC) for 15,30,60 seconds. Twelve normal subjects were included in this study. The author came to following conclusions from the results. 1. MMF of anterior temporal muscle in the contraction period was significantly higher than that of masseter muscle during sustained isometric contraction regardless of isometric contraction times (p<0.05). 2. MMF in the contraction period decreased as the contraction time increased during sustained isometric contraction in both temporal and masseter muscles(p<0.05). 3. SMF in the contraction period increased as the contraction tie increased during sustained isometric contraction in both temporal and masseter muscles(p<0.01). 4. MMF in the first part of recovery period (20 seconds) decreased as the contraction time increased during sustained isometric contraction(p<0.05). However, MMF in the later parts of recovery period (20-120 seconds) showed no significant differences. 5. MMF of anterior temporl muscle in the recovery period was significantly higher than that of masseter muscle after sustained isometric contraction regardless of isometric contraction times (p<0.05). 6. The recovery rate of MF reached 100% in 100 seconds after the isometric contraction regardless of isometric contraction times.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.6 no.1
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• pp.59-65
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• 2012

In this study, muscle fatigue of biceps and triceps during isometric exercise depending on concentric contraction and eccentric contraction was evaluated using EMG. 12 healthy male volunteers was performed concentric exercise and eccentric exercise by maximum flection and extension of elbow joint. Integrated EMG (IEMG) in time domain and mean power frequency (MNF) in frequency domain were calculated. MNF of the biceps and triceps was decreased, whereas IEMG was increased during concentric contraction and eccentric contraction. But muscle fatigue index appeared higher at region of stretched muscle length. in this result, muscle fatigue occurs at both biceps and triceps muscle during concentric and eccentric exercise, and muscle fatigue was affected by muscle contraction and extension.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.153-160
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• 2000

Occupational cumulative traumas (CTDs) are becoming one of leading ailments in industrialized worl $d^{(1.2)}$. The degree of muscle fatigue is important parameter to understand cause of occupational cumulative trauma disorders. To quantify degree of muscle fatigue, muscle EMG activity was measured during isometric and dynamic contractions(repetitive concentric/eccentric muscle contraction) and its analyzed data, such as RMS, median frequency, and median power were compared when the muscle was fresh and exhausted. When muscle become fatigue, it was observed that median frequency decreased and median power and RMS increased However, based on overall prolonged observation, median frequency increased and median power and RMS decreased. Therefore it was concluded that shifting patterns of RMS, median frequency, and median power values can be used as parameter to evaluate degree of muscle fatigue even in dynamic muscle contraction.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.141-146
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• 2008

The purpose of this study is to develop the algorithm which can control muscle power assist robot especially for elderly. Recently, wearable robots for power assistance are developed by many researchers, and its application fields are also variable such as for medical or military equipment. However, there are many technical barriers to develop the wearable robot. This study suggest a control method improving performance of a wearable robot system by using a EMG signal of major muscles and a force sensor signal as command signal of system. The result of the robot Prototype efficiency experiment, the case of Maximum Isometric motion it suggest 100% power of muscle, the man need only 66% of MVIC(Maximum Voluntary Isometric Contraction) to lift 5kg dumbbell without robot assist. However the man needs only 52% of MVIC to lift 5kg dumbbell with robot assist. Therefore 20% muscle power increased with robot assist. Also, we designed light weight robot mechanism that extract the command signal verified and drive the wanted motions.

• The Journal of Korean Physical Therapy
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• v.10 no.2
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• pp.33-40
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• 1998

This study was carried out to investigate the muscle strength of quadriceps muscles by means of isokinetic test. The experimental objects were devided into electrically stimulated, isotonic and isometric groups and trained for 4weeks. The results were as follows : 1. the values of total work, peak torque, average power and the ratio of peak torque between flexors and extensors revealed singnificant statistically in three experimental groups(p<0.05). 2. The endurance was increased slightly in electrically stimulated group, but decreased in isotonic and isometric group, 3. The value of post training on all items did not reveal significant statistically in three experimental groups(P>0.05). 4. The electrically stimulated groups effected on increasing of muscle strength as isotonic and isometric exercises.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.115-124
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• 2008

The purpose of this study was to know influenced on the change of Oswestry back pain disability index(OBPDI), isometric muscle power(IMP), muscular activation with chronic low back pain(CLBP) patients after Trunk Stabilization Exercise. Intervention was provided 6 weeks(5 days a week). Muscular activation was measured during IMP(Muscles : transversus abdominis : TA, internal obliqus : IO, external obliqus : EO, rectus abdominis : RA and erector spinae: ES). The results were as follows. 1. OBPDI about the MBE and the SE groups had effective decrease pain and disability. 2. IMP of intervention after the MBE and the SE groups had effective improve muscle power. 3. Muscle activation during IMP of intervention after was : TA, IO, RA had increase in the MBE and the SE groups. EO muscle activation during IMP of intervention after had increase only MBE groups. This shows that the MBE and the SE groups had effective increase because it has effective improve muscle power. Therefore, this study shows ￡hat trunk stabilization exercise program influenced on the change of OBPDI, IMP, muscular activation with CLBP patients.

• Journal of the Ergonomics Society of Korea
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• v.22 no.2
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• pp.57-69
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• 2003

This study was performed to investigate the isometric endurance time as percentages of maximum voluntary contraction. Electromyogram(EMG) and Borg's CR-I0 value were measured by push-pull-up-down tasks for 10 healthy males. The normalized EMG value and the MPF(mean power frequency) were used to estimate the muscle recruitment pattern and the development of muscle fatigue. The subjects exerted and maintained 5 levels of %MVC(maximum voluntary contraction) in $90^{\circ}$ shoulder flexion/ 180oelbow extension at sitting posture. The up-task showed the lower endurance time and higher Borg's CR-I0 value than the other task types. Comparing Rohmert's curve with the endurance time of task types. Rohmert's curve overestimated the endurance time of up-task and underestimated the endurance time of push-pull-down tasks. The normalized EMG value showed that muscles recruitment patterns were different from task types. The 4 muscles(biceps brachii muscle, tricep brachii muscle. middle deltoid muscle. trapezius muscle) recruitment patterns of up-task were higher than those of other tasks. The MPF value decreased with the endurance time, and the shift of MPF at up-task was larger than that of the other task types.

• Korean Journal of Applied Biomechanics
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• v.25 no.3
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• pp.275-281
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• 2015

Objective : In order for Taekwondo athletes to perform destructive kicking performance, they are expected to have Taekwondo-specific muscle properties such as high muscle strength and power. The purpose of this study was to investigate the joint angle-dependent force-producing property of Taekwondo athletes' knee extensor muscles, which is one of the primary muscle groups involved in kicking performance. Method : Ten Taekwondo male athletes (age: $19.9{\pm}0.7yrs$, height: $180.6{\pm}6.2cm$, body mass: $75.9{\pm}8.9kg$, career: $9.2{\pm}2.9yrs$.) and 10 healthy male non-athletes (age: $26.3{\pm}2.6yrs$, height: $174.2{\pm}4.8cm$, body mass: $72.8{\pm}7.7kg$) participated in this study. Subjects performed maximum isometric knee extension at knee joint angles of $40^{\circ}$, $60^{\circ}$, $80^{\circ}$, and $100^{\circ}$ (the full knee extension was set to $0^{\circ}$) with the hip joint angles of $0^{\circ}$ and $80^{\circ}$ (the full extension was set to $0^{\circ}$). During the contractions, knee extension torque using an isokinetic dynamometer simultaneously with muscle activities of the rectus femoris (RF), and the vastus lateralis (VL) and vastus medialis (VM) using surface electromyography were recorded. Based on the torque values at systematically different knee-hip joint angles, the joint torque-angle relationships were established and then the optimal joint angle for the knee extensor was estimated. Results : The results of this study showed that the isometric knee extension torque values were greater for the Taekwondo athletes compared with the non-athlete group at all hip-knee joint angle combinations (p<.05). When the hip joint was set at $80^{\circ}$, the peak isometric torque was greater for the Taekwondo athletes compared with the non-athlete group ($313.61{\pm}36.79Nm$ and $221.43{\pm}35.92Nm$, respectively; p<.05) but the estimated optimum knee joint angles were similar ($62.33{\pm}5.71^{\circ}$ and $62.30{\pm}4.67^{\circ}$ for the Taekwondo athletes and non-athlete group, respectively). When the hip joint was set at $0^{\circ}$, the peak isometric torque was greater for the Taekwondo athletes compared with the non-athlete group ($296.29{\pm}45.13Nm$ and $199.58{\pm}25.23Nm$, respectively; p<.05) and the estimated optimum knee joint angle was larger for the Taekwondo athletes compared with the non-athlete group ($78.47{\pm}5.14^{\circ}$ and $67.54{\pm}5.77^{\circ}$, respectively; p<.05). Conclusion : The results of this study suggests that, compared with non-athletes, Taekwondo athletes have stronger knee extensor strength at all hip-knee joint angle combinations as well as longer optimum muscle length, which might be optimized for the event-specific required performance through prolonged training period.

• Journal of the Korean Society of Physical Medicine
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• v.8 no.4
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• pp.593-600
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• 2013

PURPOSE: We investigated the relationship between personality, music type and MVIC, power for the knee extensor on inducing muscle fatigue. METHODS: The subjects of this study were 22 healthy students. MVIC(Maximum Voluntary Isometric Contraction) and power in knee extension was measured by PRIMUS RS. Personality types was measured by MBTI(Myers-Briggs Type Indicator) that is an instrument designed to provide descriptive profiles of personality types and preferences. The collected data were analyzed using the independent t-test, MANOVA and Pearson-test. RESULTS: There was no significant differences both MVIC and power of the knee extensor according to personality and music type. The power was significantly increased by increasing the MVIC during a knee extension on inducing muscle fatigue without music type(r= .786~.896). There was no significant correlation both MVIC and power of the knee extensor according to personality. CONCLUSION: There was a positive correlation between power and MVIC during a knee extension on inducing muscle fatigue without music type. There was no significant correlation both MVIC and power of the knee extensor according to personality.