• Journal of the Korean Society of Physical Medicine
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• v.5 no.3
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• pp.405-412
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• 2010

Purpose : The purpose of this study was to assess the effects of the trunk muscle activity on bridging exercise according to the knee joint angle. Methods : Twenty-five healthy adults volunteered to participate in this study. Subjects were required to complete following four bridging exercises; knee joint flexion $120^{\circ}$, $90^{\circ}$, $60^{\circ}$, $45^{\circ}$. Surface electromyography from selected trunk muscles was normalized to maximum voluntary isometric contraction. Muscle activity was measured by QEMG-4 system(LXM 3204, Laxtha Korea). A repeated measures of one-way ANOVA with post-hoc Bonferroni's correction was used to determine the influence of bridging exercise on muscle activity for each muscle and descriptive statistics was used to determine local/global muscle ratio. Results : The internal oblique of bridging exercises $120^{\circ}$, $90^{\circ}$ showed significantly(p<.05). The erctor spinae of all bridging exercises showed significant excepted between $60^{\circ}$ and $45^{\circ}$(p<.05). Median of internal oblique/rectus abdominis ratio of $120^{\circ}$ was 4.41, $90^{\circ}$ was 3.94, $60^{\circ}$ was 3.58, $45^{\circ}$ was 3.39. Median of internal oblique/external oblique ratio of $120^{\circ}$ was 2.66, $90^{\circ}$ was 2.43, $60^{\circ}$ was 2.87, $45^{\circ}$ was 2.64. Conclusion : Angular motion decreasing with knee joint flexion made erector spinae activation increase. on the other hand, as decreasing abdomen muscle activation, the more performing motor learning is required for abdomen muscle strength and co-contraction for the trunk stabilization.

• Journal of Biomedical Engineering Research
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• v.31 no.4
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• pp.310-315
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• 2010

Estimation of muscle forces is important in biomechanics, therefore many researchers have tried to build a muscle model. Recently, optimization techniques for adjusting muscle parameters, i.e. EMG-driven model, have been used to estimate muscle forces and predict joint moments. In this study, an EMG-driven model based on the previous studies has been developed and isometric and isokinetic contraction movements were evaluated to validate the developed model. One healthy male participated in this study. The dynamometer tasks were performed for maximum voluntary isometric contractions (MVIC) for ankle dorsi/plantarflexors, isokinetic contraction at both $30^{\circ}/s$ and $60^{\circ}/s$. EMGs were recorded from the tibialis anterior, gastrocnemius medialis, gastrocnemius lateralis and soleus muscles at the sampling rate of 1000 Hz. The MVIC trial was used to customize the EMG-driven model to the specific subject. Once the subject's own model was developed, the model was used to predict the ankle joint moment for the other two dynamic movements. When no optimization was applied to characterize the muscle parameters, weak correlations were observed between the model prediction and the measured joint moment with large RMS error over 100% (r = 0.468 (123%) and r = 0.060 (159%) in $30^{\circ}/s$ and $60^{\circ}/s$ dynamic movements, respectively). However, once optimization was applied to adjust the muscle parameters, the predicted joint moment was highly similar to the measured joint moment with relatively small RMS error below 40% (r = 0.955 (21%) and r = 0.819 (36%) and in $30^{\circ}/s$ and $60^{\circ}/s$ dynamic movements, respectively). We expect that our EMG-driven model will be employed in our future efforts to estimate muscle forces of the elderly.

• Annals of Clinical Neurophysiology
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• v.5 no.2
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• pp.187-191
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• 2003

Purpose: MEPs elicited by transmagnetic stimulations of the motor cortex are facilitated by voluntary muscle contraction. We evaluated the effects of the imagination of the movements on latencies of MEPs and reciprocal inhibition by using transmagnetic stimulations. Methods: Twenty two healthy volunteers(eight men and fourteen women) were studied. TMSs were delivered at rest and during imagining abducting or adducting right thumb. A stimulator with a round coil and a fixed intensity of 80% of maximum was used to evoke MEPs. MEPs were evoked by magnetic stimulations over the scalp and cervical spine(C7-T1), and central motor conduction times(CMCT) were calculated by subtracting the latency of compound muscle action potentials(CMAPs) obtained by stimulating over the cervical spine from that obtained by stimulating over the scalp. The motor evoked potentials were recorded from right abductor pollicis brevis muscle(APB) and adductor pollicis muscle(AP) simultaneously. Results: Imagination of abduction resulted in a shortened latency of the CMAPs in APB, and a prolonged latency in AP. Imagination of adduction resulted in a shortened latency in AP, and a prolonged latency in APB. But the imagination caused no significant change in the latency of CMAPs elicited by stimulation over cervical spine. Therefore, the changes of the CMCTs account for these latency changes with imagination of movement. With the imagination of abduction, there are significant reduction of the CMCT's in APB(10.8%) and prolongation in AP(5.8%). On the other hand, with the imagination of adduction, prolongation of the CMCT's in APB(7.3%) and reduction in AP(5.9%) were observed. Conclusion: These findings indicate that imagination of muscle contraction increases the excitability of the human corticospinal system. Reciprocal inhibition may be accountable for the prolonged latency in the antagonist muscle.

• Journal of The Korean Society of Integrative Medicine
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• v.9 no.1
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• pp.133-140
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• 2021

Purpose: This study aimed to compare the relative muscle activity on the erector spinae, gluteus maximus, and hamstring, using a non-visual feedback bridge exercise and a visual feedback bridge exercise with a tension sensor and clinometer. Methods: Twenty-two healthy subjects participated in this study. The study subjects performed bridge exercises without visual feedback, bridge exercises using a tension sensor, and bridge exercises using an inclinometer in the supine position, and the muscle activity of the left and right erector spinae, gluteus maximus, and hamstring muscles was measured while maintaining isometric contraction during the bridge movement. Muscle activity was measured by using surface an electromyography equipment. To standardize the measured action potential of each muscle, the maximum voluntary isometric contraction was measured. The bridge exercise was repeated 3 times for 5s each. Using repeated analysis of variance, we compared the significant difference in EMG activity for each muscle between the three experiments, and all statistical processing was performed using SPSS version 26. The statistical significance level was set at α = 0.05. Results: During bridging exercises, the asymmetry of the muscle activity of the erector spinae and gluteus maximus during visual feedback guiding was lower than that during no visual feedback. However, there was no significant difference. Moreover, the asymmetry of the muscle activity of the hamstring muscles was significantly lower during tension sensor visual feedback than that during no visual feedback (p<0.05). Conclusion: These findings suggest that bridge exercise with visual feedback using a tension sensor and an inclinometer is effective in inducing symmetrical movement. When it is necessary to symmetrically adjust the weight load of both feet during the bridge exercise, it is effective to apply visual feedback using a tension sensor.

• Korean Journal of Applied Biomechanics
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• v.17 no.2
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• pp.41-50
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• 2007

The purpose of this study was to examine the effects of Task-oriented training on the balance, lapse time and MVC(Maximum Voluntary Contraction) of CVA(cerebral vascular accident) patients. The active balance equipment was used to measure of the static balance, lapse time and task-oriented training. The EMG technique was used to record muscle activitie of affected side of gluteus medius and vastus medialis. The raw EMG data were filtered with band pass filter (60Hz) to remove artifacts and then low pass filtered (20Hz) to find the linear envelope which resemble muscle tension curve. The experiment had been conducted at the department of physical therapy in J hospital in M city during 8weeks. The thirty patients experienced the stroke were participated: training group (15), control group (15). They were ambulatory with or without an assistive device. They were assessed on central perturbation(mm) in the static balance, lapse time(s) and MVC test(mV). The data were analyzed using repeated measured ANOVA. The results were as follows: After Task-oriented training, central perturbation and lapse time was significantly differences in both groups(p<.001), and MVC in gluteus medius were no significant differences in both groups, but vastus medialis was significant differences in both groups (p<.001).

• Journal of Biomedical Engineering Research
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• v.27 no.2
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• pp.73-77
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• 2006

Prolonged immobilization leads to significant weakness and atrophy of the skeletal muscle and can also impair the recovery of muscle strength following injury. Therefore, it is important to minimize the period under immobilization and accelerate the return to normal activity. This study examined the effects of combined heat treatment and rest-inserted exercise on the muscle activity of the lower limb during knee flexion/extension. Twelve healthy subjects were assigned to 4 groups that included: (1) heat treatment + rest-inserted exercise; (2) heat treatment + continuous exercise; (3) no heat treatment + rest-inserted exercise; and (4) no heat treatment + continuous exercise. Heat treatment was applied for 15 mins prior to exercise. Continuous exercise groups performed knee flexion/extension at 0.5 Hz for 300 cycles without rest whereas rest-inserted exercise groups performed the same exercise but with 2 mins rest inserted every 60 cycles of continuous exercise. Changes in the rectus femoris and hamstring muscle activities were assessed at 0 and 2 weeks of treatment by measuring the electromyography signals of isokinetic maximum voluntary contraction. Significant increases in both the rectus femoris and hamstring muscles were observed after only 2 weeks of treatment when both heat treatment and rest-inserted exercise were performed. These results suggest that combination of various treatment techniques, such as heat treatment and rest-inserted exercise, may accelerate the recovery of muscle strength following injury or immobilization.

• 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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.7
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• pp.910-916
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• 2018

In this paper, we developed a shoulder rehabilitation exercise device and monitoring system to remotely provide rehabilitation system for the ones who need shoulder exercises including the patients with rotator cuff rupture. In order to evaluate the severity of shoulder muscle injury, a total of 4 shoulder rehabilitation exercises ((3) shoulder abduction, (2) shoulder flexion, (3) shoulder abduction with elbow flexion, (4) shoulder extension with elbow flexion) were selected and instructed to be performed with a 3 kg dumbbell for 5 times. For EMG (electromyogram) signal analysis, each subject's maximum voluntary contraction (MVC) was measured. EMG signals reflect the activation level of contracting muscles during dynamic exercises. Six participants' muscle activation levels in posterior deltoid, middle deltoid, upper trapezius, and infraspinatus were measured and compared. The mean power spectrum values in the time and frequency domains were compared between two age-matched groups (20s and 50s). The results showed lower muscle activation in the elderly subjects (n=3) compared to that of the ones in their twenties (n=3).

• Journal of Biomedical Engineering Research
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• v.32 no.1
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• pp.1-6
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• 2011

An active training system has been developed to assist the upper extremity function in patients with spasticity. We also evaluated the performance of the developed assistive system in five normal subjects and one hemiplegic patient. The maximum voluntary contraction (MVC) tests for biceps brachii and triceps brachii were performed and the relationship between linear enveloped EMG signal and the elbow joint torque was found. In order to implement an active training, our system was designed to allow isokinetic movement only when the subject generates elbow joint motion larger than the pre-fixed threshold level. The proposed EMG-feedback control method could provide active exercises, resulting in better rehabilitation protocol for spastic patients.

• Journal of the Ergonomics Society of Korea
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• v.26 no.4
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• pp.41-47
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• 2007

This paper suggested the best work conditions including short break time and the number of mouse clicks on the computer work for the prevention of MSDs on VDT work. Fatigue measures included EMG based parameters. The short break time conditions are grouped into 7, 15, and 30 seconds after every work for 10 min and the number of mouse clicks are divided into 10, 20, and 30 clicks/min. The result of the ANOVA of the shift value of %MVC(Maximum Voluntary Contraction) showed the following: 1) There was a considerable difference as regards to the break time except the number of mouse clicks on the upper trapezius muscle(p$<$0.05). The best conditions were shown in 15 sec after every 10 min and 30 clicks/min. 2) There were considerable differences as regards to the number of mouse clicks except the break time on the extensor digitorum muscle and extensor carpi ulnaris muscle(p$<$0.05). The best conditions were shown in 7 sec after every 10min and 10 clicks/min.