• The Journal of Korean Physical Therapy
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• v.28 no.3
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• pp.212-216
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• 2016

Purpose: The current study seeks to identify the relationship between torque values of the quadriceps and muscle activity during isometric and isokinetic exercises. Methods: The subjects of the study included 29 healthy individuals 17 men and 12 women) who took part in isometric and isokinetic exercises that utilized the quadriceps. The isometric exercises were performed three times each at 4 different angles (0, 30, 60, and 90 degrees). For the isokinetic exercises, concentric contraction and eccentric contraction were undertaken three times each at two angular velocities (30 and 60 degrees). Results: The muscle activity of the quadriceps during the isometric exercises showed significant differences at the 30, 60, and 90 degree angles. During the concentric contractions and eccentric contractions, muscle activity at the peak torque of the quadriceps indicated significant differences in vastus medialis, vastus lateralis, and rectus femoris at angular velocities of 30 and 60 degrees. Conclusion: When applied clinically based on the biomechanical analysis of the current study, it is possible to anticipate and selectively strengthen muscles with isometric and isokinetic exercises for not only healthy adults and professional athletes, but also for those who experience limited knee movement for long periods following knee surgeries.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.1
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• pp.55-63
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• 2003

In this study was proposed that a new estimating method for investigation of contractile state changes which generated from continuous isometric contraction of skeletal muscle. The physiological changes(EMG, ECG) and the psychological changes by CNS(central nervous system) were measured by experiments, while the muscle of subjects contracted continuously with isometric contraction in constant load. The psychological changes were represented as three-step-change named 'fatigue', 'pain' and 'sick(greatly pain)' from oral test, and the method which compared physiological change with psychological change on basis of these three steps was developed. The result of analyzing the physiological signals, EMG and ECG signal changes were observed at the vicinity of judging point in time of psychological changes. Namely, it is supposed that contractile states have three kind of states pattern (stable, fatigue, pain) instead of two states (stable, fatigue).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1628-1633
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• 2017

The purpose of this study was to identify the difference and correlation in elbow joint maximal flexion strength according to measurement methods and characteristics of muscular contraction, and to develop the predictive equation of elbow joint maximal flexion strength for the optimal exercise intensity setting and accurate measurement. Subjects were 30 male university students. Elbow joint maximal flexion strength of isokinetic contraction, isometric contraction at $75^{\circ}$ elbow joint flexion position, isotonic concentric 1RM, manual muscle strength (MMT) were measured with isokinetic dynamometer, dumbbell, and manual muscle tester. Pearson's r, linear regression equation, and multiple regression equation between variables were calculated. As a result, the highest value was isometric contraction. The second highest value was MMT. The third highest value was isokinetic contraction. 1RM was the lowest. Predictive equations of elbow joint maximal flexion strength between isometric and isokinetic contraction, between isometric contraction and 1RM, among isometric contraction, 1RM, and body weight were developed. In conclusion, 1RM and isokinetic elbow joint maximal flexion strength could be seemed to underestimate the practical elbow joint maximal flexion strength. And it is suggested that the developed predictive equations in this study should be useful in criteria- and goal-setting for resistant exercise and sports rehabilitation after elbow joint injury.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.3 no.1
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• pp.1-12
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• 2005

This study aimed at examining the maximal isometric contraction caused by voluntary exercise and at comparing its aspects of decrease and restoration in their different repeated application, as to the quadriceps muscles of thigh in the subjects composed of patients with spastic hemiplegia and normal adults. Using isokinetic exercise analyser(Biodex Medical Systems Inc., Biodex System 3PRO, U.S.A.), experiment was conducted as to the normal group composed of fifteen adults and the patient group composed of fifteen patients with spastic hemiplegia. As to each group, MVIC(maximal voluntary isometric contraction) of the quadriceps muscle of thigh caused by voluntary exercise and the aspects of decrease and restoration of the isometric contraction were examined with the method to induce isometric exercise, and their SDI(strength decrement index) and SRI(strength recovery index) were also calculated. The results can be summarized as follows: 1. As for decrease of maximal isometric contraction, both groups showed slow decrease in voluntary exercise, but the normal group showed rapid decrease later phase. 2. As for SDI, no significant differences could be observed in comparison between groups. 3. As for restoration of maximal isometric contraction, both groups showed slow restoration in voluntary exercise, but the normal group showed rapid restoration early phase. 4. As for SRI, comparison between groups showed significant differences in voluntary exercise. These results lead us to the conclusions that spastic muscle is characterized by slow decrease and restoration of MVIC in comparison with normal muscle in voluntary exercise.

• Physical Therapy Korea
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• v.1 no.1
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• pp.75-82
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• 1994

The purpose of this study is to determine cardiovascular reponses to concentric, eccentric and isometric exercise applied to the knee extensor muscle group. Exercise types studied were concentric, eccentric and isometric. The subjects were sixty healthy male volunteers who had no hypertension or cardiac disease. Heart rate, systolic and diastolic blood pressure were recorded prior to starting exercise. The subjects also performed 10RM on right lower extremity. A N-K table was used for three exercises to right knee extensors. Each exercise was selected randomly and applied to each subject 10 times in a 10 second. After each exercise, heart rate, systolic and diastolic blood pressure were recorded immediately. Findings were as follows concectric contractions had a greater effect on the increase of systolic blood pressure and heart rate than eccentric or isometric contractions. Diastolic blood pressure is influenced only by isometric contractions. Eccentric contractions have less effect on the increase of systolic blood pressure and heart rate than concentric or isometric contractions. We hope that the results of this experiment can be adapted to exercise programs for patients with cardiac disease.

• Physical Therapy Korea
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• v.17 no.2
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• pp.1-9
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• 2010

To develop effective training methods for strengthening a weakened quadriceps femoris muscle in hemiplegic patients, we examined the effects of maximal isometric contraction of the nonparalyzed knee joint on the electromyographic activities of the paralytic muscle. An electromyogram (EMG) was used to record the electromyographic activities of the paralytic quadriceps femoris muscle in 27 hemiplegic patients. The maximal isometric contraction was measured for each subject to normalize the electromyographic activities. The maximal isometric extension and flexion exercises were randomly conducted when the knee joint angles of the nonparalyzed knees were $0^{\circ}$, $45^{\circ}$, and $90^{\circ}$. The patients were encouraged to maintain maximal isometric contractions in both knee joints during each measurement, and three measurements were taken. A one-minute rest interval was given between each measurement to minimize the effects of muscle fatigue. An average from the three values was taken as being the root mean square of the EMG and was recorded as being the maximal isometric contraction. The electromyographic activity obtained for each measurement was expressed as a percentage of the reference voluntary contraction, which was determined using the values obtained during the maximal isometric contraction. The results of this study are summarized as follows: First, when the knee joint angle of the nonparalyzed knee was $0^{\circ}$, the electromyographic activities of the paralytic medial aspect of rectus femoris were related to measurement by a maximal isometric flexion exercise than by an extension exercise (p<.05). Second, when the knee joint angle of the nonparalyzed knee was $90^{\circ}$, the electromyographic activities of the paralytic lateral aspect of rectus femoris were related to measurement by a maximal isometric flexion exercise than by an extension exercise (p<.05). The results show that myoelectrical activities of paralytic quardriceps were not related to measurement angles and exercise directions of the nonparalized knee joint. Studies on various indirect intervention to improve muscular strength of patients with nervous system disorders of the weakened muscle should be constantly conducted.

• Physical Therapy Korea
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• v.8 no.3
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• pp.27-34
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• 2001

Physical therapists have been using biofeedback training to induce improvements in various circumstances. The purpose of this study was to compare the effects of visual and tactile feedback using electrical stimulation on quadriceps strength. Nineteen women without known impairment of the neuromusculoskeletal system volunteered for this study. Subjects were randomly allocated into three groups: visual feedback, tactile feedback, and control group. The torque of isometric knee extension force was measured. Subjects were asked to exert the maximal isometric contraction force of quadriceps over a 30 second period. The resting period of 10 minutes was given after the maximal isometric contraction to avoid the muscle fatigue. In between groups comparison, significant differences of the peak torque and the torque area were found on the performance of the maximal isometric contraction of quadriceps (p<.05). The values peak of torque and torque area were significantly higher during visual feedback than tactile feedback. The results of this study suggest that visual feedback is more powerful than tactile feedback (p<.01).

• Physical Therapy Korea
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• v.23 no.2
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• pp.75-83
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• 2016

Background: Several studies have discussed diverse exercise methods considered to be useful for the selective contraction of the vastus medialis oblique (VMO) muscle for the treatment of patellofemoral pain syndrome. Some studies have reported that exercise methods, including hip adduction, in closed kinetic chain exercises are more effective in terms of the muscle activation of the VMO and the timing of the muscle's initial contraction. We focused on isometric contraction during a closed kinetic chain exercise with hip adduction. Objects: The purpose of this study was to examine muscle activation in the VMO and the vastus lateralis (VL) and the onset time difference between their initial contractions via closed kinetic chain isometric quadriceps femoris exercises including hip adduction. Methods: In total, 36 healthy subjects adopted two hip positions during isometric contraction of the quadriceps femoris in a closed kinetic chain exercise (hip neutral and hip adduction position). Statistical analyses were conducted using a paired t-test (${\alpha}=.05$). Results: Isometric contraction of the quadriceps femoris in a closed kinetic chain exercise caused a greater increase in VMO muscle activity in the hip adduction position [$52.68{\pm}22.21$ percentage of maximal voluntary isometric contraction (%MVIC)]than the hip neutral position ($43.43{\pm}19.85%MVIC$). The onset time difference (VL-VMO) decreased more in the hip adduction position ($-82.14{\pm}34.2ms$) than the hip neutral position ($73.94{\pm}2.94ms$). Conclusion: We recommend this exercise as a clinically useful therapeutic method for patients with patellofemoral pain syndrome due to weakening of the VMO muscle and lateral inclination of the patella.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.5
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• pp.843-850
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• 2017

The EMG amplitude estimator, which has been investigated as an indicator of muscle force, is utilized as the control input to artificial prosthetic limbs. This paper describes an application of the optimal EMG amplitude estimator to the surface EMG signals recorded during constant isometric %MVC (maximum voluntary contraction) for 30 seconds and reports on assessing performance of the amplitude estimator from the application. Surface EMG signals, a total of 198 signals, were recorded from biceps brachii muscle over the range of 20-80%MVC isometric contraction. To examine the estimator performance, a SNR(signal-to-noise ratio) was computed from each amplitude estimate. The results of the study indicate that ARV(average rectified value) and RMS(root mean square) amplitude estimation with forth order whitening filter and 250[ms] moving average window length are optimal and showed the mean SNR improvement of about 50%, 40% and 20% for each 20%MVC, 50%MVC and 80%MVC surface EMG signals, respectively.

• Journal of the Ergonomics Society of Korea
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• v.14 no.1
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• pp.9-23
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• 1995

The objectives of the study were twofole: (1) to investigate effects of rhythmic contraction and sustained contraction methods on recovery rate of isometric endurance capacity and (2) to compare aptterns of muscle recruitment of both arms observed during each contraction period. In the experiment, each of two subjects performed five successive rhythmic or sustained isometric contractions at 50% MVC with both arms to the point of fatigue, which was the failure to maintain the required tension. In making the contractions, the subjects stood erect with upper arms held at an angle of approximately 90 .deg. to the forearm. The interval between the successive contractions was kept constant at 3, 7, 20, or 40 minutes. Regardless of the contraction methods, the recovery rate was least at the shortest interval and was highest at the longest interval. However, a statistical analysis showed that the recovery rates for the rhythmic contractions were significantly lower than those for the sustained contractions throughout 4 different intervals. Furthermore, as the frequency of the rhythmic contractions per min, increased 4 to 6 times, the recovery rate of isometric endurance capacity decreased. From an EMG anglysis, recruitment pattern of the muscules of both arms was found to be common between two different contraction methods. The biceps muxcles of the upper arms played a major role in exerting 50% MVC, while the brachioradialis muscles of the forearms acted as synergists. As the contraction proceeded, the role of the biceps muscles as a prime mover lessened due to the fatigue. Then, the brachioradialis muscles exerted more strength to sustain 50% MVC. The implications of these finding were discussed.