• Journal of International Academy of Physical Therapy Research
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• v.11 no.2
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• pp.2071-2076
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• 2020

Background: Based on the understanding of the muscle activation relationship between the infraspinatus and posterior deltoid muscles to according to the angle of motion during external rotation on glenohumeral joint, effective shoulder joint strengthening exercise for the prevention and rehabilitation of shoulder injury due to muscle strength imbalance can be performed by achieving the ideal muscle activity ratio during exercise. Objectives: To compare and analyze the muscle activation changes and activity ratio of the infraspinatus and posterior deltoid muscles according to the glenohumeral external rotation angle. Design: Quasi-randomized trial. Methods: The study included 48 healthy male and female adults who provided informed consent for participation in the study. All the subjects performed isometric glenohumeral external rotation by setting the angle of motion to 30°, 45°, and 60° using a 5 kg resistance weight pulley. On surface electromyography, the differences in muscle activation and activity ratio between the infraspinatus and posterior deltoid muscles were investigated. Results: A significant difference in muscle activation was found in the comparison between the infraspinatus and posterior deltoid muscles according to the glenohumeral external rotation angle (P<.05). The muscle activation levels of the infraspinatus and posterior deltoid muscles were highest at the external rotation angles of 30° and 60°, respectively. The muscle activity ratio between the infraspinatus and posterior deltoid muscles also showed a significant difference (P<.05) and was highest at the shoulder external rotation angle of 30°. Conclusion: The findings of this study suggest that muscle activity is the highest at the shoulder external rotation angle of 30° in healthy individuals.

• PNF and Movement
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• v.13 no.2
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• pp.95-102
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• 2015

Purpose: The purpose of this study was to analyze the effect of arm flexion patterns of proprioceptive neuromuscular facilitation on muscle activation in the contralateral lower extremity. Open kinematic chain and closed kinematic chain positions were used. Methods: This study used an electromyogram (MP150, Biopac Systems, USA) to measure muscle activation in 20 healthy male students. Comparative analysis was completed on muscle activation of the vastus lateralis, biceps femoris, tibialis anterior, and gastrocnemius of the contralateral lower extremity. Open kinematic chain and closed kinematic chain positions were used with a unilateral arm flexion-abduction-external rotation pattern. Paired t-tests using the SPSS 12.0 for Windows analyzed the data produced by the electromyogram. Results: There was a statistically significant difference in muscle activation in the biceps femoris, gastrocnemius, and tibialis anterior when the open kinematic chain and closed kinematic chain positions were compared (p < 0.05). Conclusion: The biceps femoris, gastrocnemius, and tibialis anterior muscles showed greater muscle activation in the closed kinematic chain position when compared to the open kinematic chain position.

• Journal of the Korean Society of Physical Medicine
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• v.6 no.1
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• pp.93-101
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• 2011

Purpose : The purpose of this study was to investigate the effects of maximum muscle activation of lower extremity of facility dwelled elderly Hansen's disease after isometric trunk exercise for 12weeks. Methods:18 elderly Hansen's disease who isometric trunk exercise for 12weeks were recruited for this study. They were instructed to perform maximum muscle activation of lower extremity after exercise. and the subjects were divided into normal sensory group, sensory loss in left foot group, sensory loss in right foot group and sensory loss in both feet group, according to the sensory condition ability on their soles. Results : After exercise, Hamstring muscle increased significantly (p<.05), and activation of the rectus femoris muscle decreased with a significance (p<05). In terms of Post-hoc test for examining the difference in MVIC according to sensory condition, there was significant difference in the normal sensory group, sensory loss in right and left foot group of left hamstring muscle before the exercise(p=.01) and the normal sensory group, sensory loss in both feet group of right hamstring muscle before the exercise(p=.04). Conclusion : These results indicate that the maximum muscle activation was changed after isometric trunk exercise. it could be improved maximum muscle activation of lower extremity muscle after the exercise although there was sensory loss.

• Journal of Korean Physical Therapy Science
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• v.24 no.2
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• pp.36-44
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• 2017

Background: To determine the effect of proprioceptive exercise(PE) on muscle activation and balance of healthy subjects. Methods: 20 subjects were randomly assigned to proprioceptive exercise(PE, n=10) and general exercise group(GE, n=10). To measure muscle activation of the lower limb and balance. For evaluation of muscle activation(Tibialis anterior, Gastrocnemius lateral and medial head), the Electromyogram was used, and balance was measured using the one-leg standing test, OLST. Results: Tibialis anterior(TA), Gastrocnemius medial head(GM) and Gastrocnemius lateral head(GL) muscle activations were significantly (p<0.05) improved in PE group and GE group. and significantly difference between groups(p<0.05). Regarding balance, eye open and close OLST were significantly (p<0.05) increased in PE group and GE group. and significantly difference between groups(p<0.05). Conclusion: Proprioceptive exercise can improve muscle activation of the lowe limb and balance in subjects.

• The Journal of Korean Physical Therapy
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• v.31 no.2
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• pp.76-81
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• 2019

Purpose: This study examined the effects of squatting with different foot positions on the muscle activation of the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles in subjects with genu varum. Methods: Thirty four subjects participated in this study. Surface electromyography was used to measure the muscle activation of the VMO and VL muscles at the knee angles ($15^{\circ}$, $60^{\circ}$) at three foot positions (internal rotation, neutral position, external rotation) during squatting. Results: Muscle activation differences at different knee angles and foot positions differed significantly between the VMO and VL muscles in both the varus and normal groups. In addition, there was a significant difference according to the knee angles with the foot in external rotation in the VMO and VL ratio. In the varus group, however, the VMO and VL ratio were significantly different only with the feet in internal rotation. In the muscle activation changes of the knee angle differences in the foot position, there was no significant difference in the varus group, but both the VMO and VL muscles were significant different in the normal group. Conclusion: In both groups, regardless of the foot position, muscle activation of the VMO and VL muscles increased with increasing knee flexion angle. In the normal group, when squatting with the feet in external rotation, the VMO and VL muscles activations increased with increasing knee angle. In the varus group, however, the foot position did not affect the VMO or VL muscle activation. This study shows that subjects with genu varum and normal subjects have different VMO and VL muscle activation patterns during squat exercises.

• Journal of Korean Physical Therapy Science
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• v.31 no.3
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• pp.89-99
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• 2024

Background: Squats are well-known for their effectiveness in strengthening the quadriceps femoris muscle. Flexibility and stability of the ankle joint are critical factors in performing squats correctly. Ankle instability can lead to injuries owing to compensatory actions. The role of the soleus muscle in maintaining ankle balance is crucial to minimize the risk of injury. Moreover, squats on unstable surfaces have gained attention for their potential to enhance balance and stability, which in turn helps prevent injuries. Therefore, this study aims to investigate the correlation between the soleus and quadriceps femoris muscles during squat exercises on various support surfaces. Design: Simple regression analysis Methods: Participants performed three different types of squats. Prior to commencing the exercises, we conducted electromyography (EMG) measurements to assess the activity of both the soleus and quadriceps femoris muscles. The order of the exercise execution was randomized. The squats were performed in a Full Squat format, and a one-minute rest was provided between each exercise type. Results: Our analysis of the results revealed significant differences in the activation levels of the soleus and quadriceps femoris across different squat types (p<.05). The regression analysis revealed an inverse relationship between the activity levels of the soleus and quadriceps femoris. Specifically, the quadriceps femoris exhibited the highest activation during squats using a wedge, while its activation was lowest during squats using the TOGU. In contrast, the soleus muscle demonstrated its highest activation during squats using the TOGU. Conclusion: Compared to traditional floor squats, the disparities in soleus and quadriceps femoris muscle activation observed during Wedge or TOGU squats can be attributed to the influence of ankle stability and balance. As the surface instability increased during squats, the soleus muscle's activity increased while the activation of the quadriceps femoris muscle decreased. These findings suggest that heightened soleus activation on unstable surfaces can significantly impact the activation of the quadriceps femoris muscle during squat exercises.

• The Journal of Korean Physical Therapy
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• v.23 no.1
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• pp.1-5
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• 2011

Purpose: The purpose of this study was to investigate changes in muscle activation associated with foot position during a sit-to-stand exercise among normally healthy elderly subjects. Methods: Eight subjects (male=3; female=5; mean age=$70.13{\pm}{\pm}2.53$years) were recruited.The activation of six muscles (neck extensor; lumbar extensor; hamstring; rectus femoris; gastrocnemius; tibialis anterior) was measured by surface EMG (TeleMyo 2400T G2, Noraxon Inc., USA) during a sit-to-stand protocol under three different foot positions (ankle dorsiflexion of 0, 15, or 30 degrees). Results: Muscle activation of the neck extensor and hamstring was decreased according to the change in foot position (p<0.05), but activation of the rectus femoris was increased (p<0.05). Muscle activation of the neck extensor was significantly different between 0 and 15 degrees (p<0.05). Muscle activation of the hamstring was significantly different between 0 and 15 degrees and between 0 and 30 degrees (p<0.05). Muscle activation of the rectus femoris was significantly different between 0 and 30 degrees and between 15 and 30 degrees (p<0.05). However, activation of lumbar extensor, gastrocnemius and tibialis anterior muscles did not significantly differ between foot positions. Conclusion: These findings suggest that muscle activation during a sit-to-stand movement differs depending on foot position. We believe that these differences should be considered when educating the elderly regarding proper body movements.

• PNF and Movement
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• v.16 no.1
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• pp.33-42
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• 2018

Purpose: The aim of this study was to investigate the effects of trapezius and serratus anterior strengthening exercise on the shoulder pain and muscle activation of patients with spinal cord injury and functional shoulder impingement syndrome. Methods: The study consisted of 10 patients with spinal cord injury who were hospitalized in Rehabilitation Hospital U, Uijeongbu, South Korea. The exercise was implemented three times a week for 10 weeks. In each session, the subjects performed one of a total of five types of exercise at mid-level intensity. The shoulder pain and disability index (SPADI) was used to evaluate the patients before and after the intervention. The muscle activation of the upper trapezius, middle trapezius, lower trapezius, and anterior serratus muscle was assessed by surface electromyography (EMG) at the beginning of the experiment and 10 weeks later. Wilcoxon's singed-rank test was conducted to determine differences in the pain index and muscle activation before and after the exercise. The level of statistical significance was set at ${\alpha}=0.05$. Results: SPADI scores significantly decreased after the exercise (p<0.05). In comparisons of muscle activation, there was a significant improvement in the upper trapezius at $60^{\circ}$ shoulder joint flexion (p<0.05). There was no significant improvement at $90^{\circ}$ shoulder joint flexion. The middle trapezius showed a significant improvement at $120^{\circ}$ shoulder joint flexion (p<0.05). Conclusion: Trapezius and serratus anterior strengthening exercise reduced pain in spinal cord injury patients with functional shoulder impingement syndrome. The decreased muscle activation of upper trapezius and increased muscle activation of the anterior serratus muscle at $60^{\circ}$ shoulder joint flexion point to positive effects of the exercise on supraduction of the scapula.

• PNF and Movement
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• v.16 no.1
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• pp.151-159
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• 2018

Purpose: The aim of this study was to examine the activation of the contralateral upper and lower extremities and trunk muscle during ipsilateral upper extremity diagonal isokinetic exercise. Methods: Twenty-one healthy male subjects with no history of shoulder injury undertook ipsilateral diagonal isokinetic exercise at 60, 120, and $180^{\circ}/sec$, utilizing a standard Biodex protocol. Muscle activation amplitudes were measured in the upper trapezius, pectoralis major, biceps brachii, rectus abdominis, external oblique, rectus femoris, adductor longus, and biceps femoris muscles using electromyography. A one-way analysis of variance and paired t-tests were conducted, and the data were analyzed using SPSS, version 21.0. Results: The results revealed no statistically significant interaction between motion and angular velocity and no statistically significant contralateral muscle activation according to angular velocity (p>0.05). However, they revealed statistically significant contralateral muscle activation according to motion (p<0.05). Conclusion: These results suggest that the movements involved in contralateral upper extremity diagonal isokinetic exercise can enhance muscle strength in patients affected by stroke, fracture, burns, or arthritis.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.11
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• pp.1476-1478
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• 1999

A musculotendon model is proposed to predict muscle force during muscle fatigue due to the continuous functional electrical stimulation(FES). Muscle fatigue dynamics can be modeled as the electrical admittance of muscle fibers and included in activation dynamics based on the{{{{ { Ca}^{2+ } }}}} kinetics. The admittance depends on the fatigue variable that monotonically increase or decrease if electrical pulse exists or not, and on the stimulation parameters and the number of applied pulses. In the response of the change in activation the normalized Hill-type contraction dynamics connected with activation dynamics decline the muscle shortening velocity and thus its force under muscle fatigue. The computer simulation shows that the proposed model can express the muscle fatigue and its recovery without changing any stimulation parameters.