• Korean Journal of Applied Biomechanics
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• v.28 no.1
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• pp.37-43
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• 2018

Objective: The aim of this study was to analyze muscle activation of the lower extremities as a function of changes of the center of pressure (CoP) of the foot during squats in order to provide quantitative information to trainers who would like to teach correct movements for developing muscles. Method: Ten men with over three years of weight training experience participated in this study (age: $26.1{\pm}0.8yrs$, height: $171.2{\pm}3.9cm$, body mass: $71.1{\pm}5.7kg$, 60%RM: $84{\pm}9kg$, career: $4.0{\pm}0.7yrs$). The participants were instructed to perform a squat in each of 3 conditions, with different CoP's (the front, middle, and rear of the foot). Results: The position of the CoP showed significant differences according to instructions in both the eccentric and concentric contraction phases (p < .05). The range of movement of the hip and ankle joints showed significant differences corresponding to changes of the CoP position (p < .05). The rectus femoris and gluteus maximus muscle showed significant differences for different CoP positions only in the concentric contraction phase, while the gastrocnemius and anterior tibialis were significantly different in both the concentric and eccentric contraction phase (p < .05). Conclusion: When the target muscle of squat training is the gastrocnemius, the CoP should be located in the front of the foot for effective muscle training. When the target muscles of squat training are the gluteus maximus and quadriceps femoris, the CoP should be located on the rear of the foot.

• Physical Therapy Korea
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• v.31 no.2
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• pp.142-150
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• 2024

Background: Scapular dyskinesis (SD) is closely related to imbalance of the rotator cuff (RC) muscles. However, previous studies have only focused on isometric strength. To our knowledge, there has been no study examining potential differences in concentric and eccentric strength and functional strength ratio (FSR) of the RC muscles based on functional parameters related to throwing in with or without SD. Objects: This study aimed to determine whether there was a difference in the RC muscle strength and FSR between the dominant shoulder with SD and the non-dominant shoulder without SD in adolescent baseball players. Methods: Forty adolescent baseball players participated and classified types of SD based on movement patterns using the SD test by two examiners. The isokinetic concentric and eccentric peak torque of the internal rotation (IR) and external rotation (ER) were measured and quantified as peak torque to body weight (PT/BW). Also, the FSR was obtained by calculating the strength ratios of eccentric IR to concentric ER (IRecc/ERcon) and eccentric ER to concentric IR (ERecc/IRcon), respectively. Results: There was a significant decrease in the IR and ER PT/BW in the dominant shoulder with SD compared to the non-dominant shoulder without SD (p < 0.05), regardless of contraction types. However, no significant difference was observed in the FSR in both IRecc/ERcon and ERecc/IRcon ratios. Conclusion: The findings indicate that the isokinetic concentric and eccentric PT/BW of the IR and ER muscles were significantly lower in the dominant shoulder with SD than in the nonthrowing shoulder without SD. Therefore, when establishing a strategy for addressing RC muscle weakness in adolescent baseball players with SD, it is essential to consider an approach that accounts for scapular kinematic recovery.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.6
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• pp.670-677
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• 2011

This study is to estimate the joint torques without torque sensor using the EMG (Electromyogram) signal of agonist/antagonist muscle with Neural Network Back Propagation Algorithm during the elbow motion. Command Signal can be guessed by EMG signal. But it cannot calculate the joint torque. There are many kinds of field utilizing Back Propagation Learning Method. It is generally used as a virtual sensor estimated physical information in the system functioning through the sensor. In this study applied the algorithm to obtain the virtual senor values estimated joint torque. During various elbow movement (Biceps isometric contraction, Biceps/Triceps Concentric Contraction (isotonic), Biceps/Triceps Concentric Contraction/Eccentric Contraction (isokinetic)), exact joint torque was measured by KINCOM equipment. It is input to the (BP)algorithm with EMG signal simultaneously and have trained in a variety of situations. As a result, Only using the EMG sensor, this study distinguished a variety of elbow motion and verified a virtual torque value which is approximately(about 90%) the same as joint torque measured by KINCOM equipment.

• PNF and Movement
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• v.22 no.1
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• pp.151-158
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• 2024

Purpose: The present study investigated how variations in diagonal exercises affect shoulder muscle activity, examining changes in neuromuscular activation during scapular and shoulder diagonal patterns of exercises. Furthermore, we explored whether the exercise phase affects muscle activation. Methods: Sixteen asymptomatic male participants were recruited. Four diagonal pattern exercises (scapular anterior elevation, posterior elevation, flexion-adduction-external rotation, flexion, abduction-external rotation), and two exercise phases (concentric and eccentric) were administered. Surface electromyography data were collected. Results: Upper trapezius activity was significantly higher during the concentric phase of scapular posterior elevation exercises compared with the others (p<0.05). The serratus anterior, anterior deltoid, and infraspinatus activities were significantly higher during shoulder diagonal pattern exercises compared with the scapular diagonal pattern exercises (p<0.05). Except for the lower trapezius, muscular activities during the concentric phase were significantly greater compared with the eccentric phase (p<0.05). Conclusion: The current study suggests that the diagonal pattern of exercise may contribute to selective strengthening of the shoulder complex muscles and that the form of exercise should be tailored to the subject. It also suggests that diagonal exercises with concentric contractions tend to be more beneficial than eccentric contractions for overall muscle recruitment, but the effects vary for specific diagonal patterns.

• 한국체육학회지인문사회과학편
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• v.54 no.5
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• pp.769-780
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• 2015

This study investigated the changes in inflammatory mediators, immunocompetent cells and bone merrow progenitor cells by the magnitude of muscle damage and type of the muscle contraction in the elderly. Twenty older adults who had not been involved in a resistance-training program at least 6 months prior to the present study were assigned to eccentric exercise group (ECC, n=10) and concentric exercise group (CON, n=10). All subjects performed 10 sets of 6 maximal isokinetic eccentric (ECC 1) or concentric (CON) contractions with the non-dominant arm in a randomized, with 4 wk between bouts (ECC 2). Skeletal muscle damage index (ROM, VAS, Plasma CK), inflammation mediators (TNF-α, IL-1, IL-6), immunocomperent cells (CD3+, CD4+, CD8+, CD19+), bone merrow progenitor cell (CD34+) and leukocytes were measured before, immediately after, 2, 24, 48, 72, and 96 h after exercise. Changes in ROM and VAS were greater (P<.05) after ECC 1 than CON and ECC 2. Increases in TNF-α and IL-6 were greater (P<.05) 24, 48 and 72 h after ECC 1 than CON and ECC 2. Increases in neutrophils were greater (P<.05) 2 h after ECC 1 than CON and ECC 2. It was confirmed that muscle damage was greater following eccentric than concentric contractions as well as first bout than second bout in the elderly, and suggested that TNF-α, IL-6 and neutrophils should closely correlate with magnitude of muscle damage.

• The Journal of Korean Physical Therapy
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• v.11 no.1
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• pp.137-141
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• 1999

Proprioceptive neuromuscular facilitation(PNF), pelvic patterns are very important for orthopaedic and neurologic patient. It is an essential treatment techniques for motor developmental disorder. CVA, lumbar disk, muscle weekness and pain control of lumbar, pelvic and lower extremity, Pelvic patterns of PNP has 4 different type of basic pattern. each of them is combinding of movement plane and functional movement. Biomechanically most of PNF patterns are a concentric contraction with third-class lever. But the movement pattern have a technique of combination of isotonic that should make a eccentric contraction with second-class lever.

• 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.

• The Journal of Korean Physical Therapy
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• v.11 no.3
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• pp.65-69
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• 1999

Proprioceptive neuromusculat facilitation(PNF), scapular patterns are very important for orthopaedic and neurologic patients. It is an essential treatment techniques for motor developmental disorder, CVA, cervical disk, frozen shoulder and pain control of cervical, shoulder girdle and upper extremity. Scapular patterns of PNF has 4 different type of pattern. each of them in combining of movement plane and functional movement. Biomechanically, most of PNF patterns are a concentric contraction with third-claw lever. But the movement pattern have a technique of combination of isotonic that should make a eccentric contraction with second-claw lever.

• The Journal of Korean Physical Therapy
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• v.16 no.3
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• pp.205-216
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• 2004

The purpose of this study is to find application of combination of insotonic(CI) in clinical approach. This is a literature study with books and clinical experience. CI was developed after Margaret Knott that is very useful in clinically. CI has two lever system. It has class II lever system for eccentric contraction and class III lever system for concentric contraction. Therefore it make two different contraction that is not only magnitude of motion and speed increase of motion but also biomechanical advantage. Application of CI has much variety by patient position and treatment position. Especially, it is very effectable on mat activities and training for mid stance period. CI apply in supine position on treatment table, mat or high mat activities, bridging activities, all fourth activities and sit on chair activities. CI apply serially with different techniques. These are rhythmic initiation, dynamic reversal, approximation, rhythmic stabilization and replication.

• Journal of the Korean Society of Physical Medicine
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• v.3 no.4
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• pp.255-260
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• 2008

Purpose : This study was performed to find out the influence of the change on proprioception and coordination of the lower limb by experimentally induced paraspinal muscle fatigue, Methods : Twelve subjects(6 males, 6 females) with no history low back and lower limbs problem volunteered for this study. Subjects were pre-tested proprioception and coordination using the MR-FSS(Mornitored Rehab Functional Squat System). And then the subjects performed isometric paraspinal muscles contraction for induced muscle fatigue. Muscle fatigue was defined surface EMG(MP 150). After isometric contraction, the subjects were post-tested using the MR-FSS. Results : In comparison of coordination, deviation of concentric coordination was increased(from $0.50{\pm}0.13cm$ to $0.67{\pm}0.21$)(p<0.05) and deviation of eccentric coordination was also increased(from $0.51{\pm}0.15cm$ to $0.70{\pm}0.26cm$)(p<0.05). And deviation movement of proprioceptive test was increased(from $4.98{\pm}1.80cm$ to $5.69{\pm}1.98cm$), but there was no significant different(p>0.05). Conclusion : Fatigue of paraspinal muscles was decreased concentric and eccentric coordination of the lower limb.