• 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.

• Physical Therapy Korea
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• v.12 no.3
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• pp.46-55
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• 2005

The purpose of this study was to evaluate the effect of concurrent and reciprocal isometric contraction and angle of ankle joint on fatigue of concentrically contracting contralateral dorsiflexor and plantar flexor. Seventeen able-bodied subjects participated in the study. Concurrent and reciprocal isometric contraction were performed under three different ankle joint angles (dorsiflexion, neutral position, plantar flexion). During concurrent or reciprocal isometric contraction. fatigue of concentrically contracting contralateral tibialis anterior, gastrocnemius, and soleus was investigated and compared. There was no interaction between different ankle joint angles and direction of isometric contraction (p<.05). No significant differences were found among three different ankle joint angles (p<.05). Contralateral muscle fatigability was lower in reciprocal isometric contraction than that in concurrent isometric contraction (p<.05). Therefore, the findings of this study suggest that reciprocal isometric contraction is more beneficial than concurrent isometric contraction inducing less fatigability during contralateral concentric contraction.

• PNF and Movement
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• v.14 no.1
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• pp.59-65
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• 2016

Purpose: The purpose of this study was to review articles in order to establish optimal contraction intensity and duration in the performance of relaxation techniques for maximal increase in range of motion. Methods: The Cochrane, EBSCO, Embase, Medline, ProQuest, PubMed, ScienceDirect, and Scopus databases were used to search articles from 1990 to January 2016. The search terms were "contract relax," "hold relax," "muscle energy technique (MET)," and "proprioceptive neuromuscular facilitation (PNF) stretching." Only experimental human studies (randomized controlled trials) that compared the effects of varying intensity and duration of isometric contraction were included. Non-English language and unpublished studies were excluded. Results: A total of 2,156 articles were initially identified, with only five eventually meeting the inclusion and exclusion criteria. Three studies compared the effects of varying intensity in isometric contraction and two studies compared the effects of varying duration in isometric contraction with regard to range of motion (ROM). Two articles suggested that submaximal voluntary isometric contraction was more effective than maximum voluntary isometric contraction (MVIC) in the improvement of ROM. One article showed that a longer contraction time led to greater increases in ROM. Conclusion: Submaximal voluntary isometric contraction was recommended during contract-relax exercises in healthy people. Lack of evidence makes it difficult to suggest the optimal duration of isometric contraction during relaxation techniques. For future research, high-quality evidence will be needed to establish the optimal contraction intensity for maximum improvement of ROM.

• 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).

• Physical Therapy Korea
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• v.22 no.3
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• pp.71-80
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• 2015

Hip muscle activation and strengthening exercise programs are often used to prevent and treat various lower extremity injuries. Common exercise programs include squat exercises. The purposes of this study were to investigate gluteus medius (GMED) and tensor fasciae latae (TFL) muscle activity, and to assess the GMED/TFL ratio during squat exercises involving different isometric hip contraction conditions. Different types of isometric hip contraction were standard squat without hip contraction, squats with isometric hip adduction, and squats with isometric hip abduction. Twenty (10 males and 10 females) healthy subjects ($23.7{\pm}2.8$ years old) were recruited. Subjects performed the squat exercises with the back supported by a wall and knees flexed to $60^{\circ}$. Surface electromyography (EMG) was used to measure GMED and TFL activity. One-way repeated analysis of variance was used to compare GMED and TFL muscle activity and the GMED/TFL ratio. GMED and TFL EMG activity was significantly higher during squats with isometric hip adduction and abduction compared with the standard squat without hip contraction (p<.05). Between the isometric hip adduction and abduction contraction conditions, only the TFL EMG activity was significantly higher during squats with isometric hip adduction than isometric hip abduction (p<.05). The GMED/TFL ratio was significantly higher during squats with isometric hip adduction than isometric hip abduction (p<.05). Squats with isometric hip adduction and abduction improved GMED and TFL muscle activity. Furthermore, the GMED/TFL ratio was higher during isometric hip adduction than isometric hip abduction. Our data indicate that squat exercises involving isometric hip adduction enhance GMED muscle activity.

• PNF and Movement
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• v.14 no.1
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• pp.49-52
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• 2016

Purpose: The purpose of the present study was to examine the effects of the area of the base of support formed by the human body on the maximal voluntary isometric contraction of upper limb muscles. Methods: The study was conducted with 20 normal adults. To identify changes in the base of support, the maximal voluntary isometric contraction of the biceps muscle was measured in a standing position, a sitting position, and a lying position for each subject. The sizes of the base of support formed in the standing, sitting, and lying positions were set to 1, 2, and 3 respectively, based on the sizes, to analyze the correlations. The maximal voluntary isometric contraction of the biceps muscle was measured using surface electromyograms (EMGs) (Noraxon DTS, Germany). Results: The results showed negative correlations in which, as the size of the base of support increased, the maximal voluntary isometric contraction of the biceps muscle decreased. Conclusion: Changes in the base of support of the body affect the maximal voluntary isometric contraction of the upper limbs. Therefore, when resistance exercises are applied for muscle strengthening, the positions should be changed considering the changes in muscle activity according to those positions. In addition, when EMGs are used to measure the maximal voluntary isometric contraction, the measurements should be conducted in the same positions, considering muscle activity that changes according to the base of support and positions, for data quantification.

• Physical Therapy Rehabilitation Science
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• v.5 no.1
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• pp.40-46
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• 2016

Objective: The purpose of this study was to examine the effect on multifidus and external oblique abdominis muscle activation during hip contraction of three types (concentric, isometric, eccentric) in standing position. Design: Cross-sectional study. Methods: Twenty healthy adult men volunteered to participate in this study. Muscle activation was recorded from gluteus maximus, both multifidus, and both external oblique abdominis by surface electromyography (EMG) while holding position in the type of gluteus maximus contraction. EMG values were normalized by maximum muscle contractions (% maximum voluntary isometric contraction). All subjects performed hip extension with three contraction methods. The type of gluteus maximus contraction using Thera-band was composed of concentric contraction (type 1), isometric contraction (type 2), and eccentric contraction (type 3). To measure muscle activation on the gluteus maximus contraction type, each position were maintained for 5 seconds with data collection taken place during middle three seconds. Muscle activation was measured in each position three times. Results: For the results of this study, there was no significant difference within three contraction patterns of the gluteus maximus (concentric, isometric, and eccentric) each both multifidus, both external oblique abdominis, and gluteus maximus. And there was no significant difference among both multifidus, both external oblique abdominis, and gluteus maximus each hip extension contraction type. Conclusions: These findings suggest that specific contraction types of the gluteus maximus does not lead to a more effective activation of the multifidus, external oblique abdominis, and gluteus maximus.

• Journal of the Korean Society of Physical Medicine
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• v.12 no.1
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• pp.61-66
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• 2017

PURPOSE: The purpose of this study was to investigate the effects of isometric upper limb contraction on the trunk and lower extremity muscles during the sit-to-stand activity in elderly females. METHODS: Eighteen healthy elderly females performed three directional isometric upper extremity contractions (flexion, extension, and horizontal abduction movements) using an elastic band during sit-to-stand activity. Electromyography signals were collected from the internal oblique, erector spinae, rectus femoris, and biceps femoris muscles. RESULTS: Internal oblique activity was greater in bilateral shoulder flexion and bilateral shoulder horizontal abduction than in neutral position (p<.05). Erector spinae and rectus femoris muscle activities in bilateral shoulder flexion was greater than in neutral position and bilateral shoulder extension (p<.05). Biceps femoris activity was significantly greater in bilateral shoulder flexion than in bilateral shoulder extension and horizontal abduction, and in neutral position compared to bilateral shoulder extension (p<.05). CONCLUSION: These results suggest that incorporating isometric upper limb contraction may be beneficial for enhancing the contribution of trunk and lower extremity muscle activities to trunk stabilization during sit-to-stand activity. Therefore, isometric upper limb contraction during sit-to-stand tasks, especially in flexion, may be used to elicit contraction of the lumbopelvic region muscles within a tolerable range, for developing endurance and strength in the elderly.

• The Korean Journal of Physiology
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• v.17 no.1
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• pp.37-43
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• 1983

Electromyographic analysis was made in the forearm to clarify the prime mover of the wrist joint in flexion and extension. Loads of 5 and 10 pounds were given to the hand during isometric and isotonic contraction. The results of this study were summarized as follows: 1) M. flexor carpi ulnaris and m. extensor carpi radialis acted as the prime mover during flexion and extension, respectively, of the wrist joint. 2) The flexor and the extensor of the forearm showed synergistic activities under isotonic contraction, but under isometric contraction the flexor only acted. 3) Muscular activity during the isotonic contraction slightly increased compared with the isometric contraction. 4) EMGs and integrated EMGs were somewhat enhanced as the load increased, but there was no significant difference between 5 and 10 pounds load.

• The Journal of Korean Physical Therapy
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• v.18 no.1
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• pp.53-64
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• 2006

Purpose: The present study purposed to examine the effects of massage and stretching on the recovery of muscle contraction force for muscle fatigue caused by sustained isometric contraction. Methods: The subjects of this study Were 64 healthy men and women (women: 30, men: 34). They Were divided into massage group (23), stretching group (21) and rest group (20), and using Biodex System we observed the pattern of changes in maximal voluntary contraction force (MVC) after causing muscle fatigue in quadriceps femoris muscle through sustained isometric contraction. Results: We measured the point of fatigue occurrence by sustained isometric contraction with 50% MVC and changes in isometric contraction force at 0, 10, 20 and 30 minutes after fatigue and compared them according to gender and treatment group. Conclusion: 1. According to the result of measuring the point of time when fatigue occurred, a difference was observed in time to task failure between men and women. It was significantly longer in women. 2. By gender, MVC changed significantly in all time frames in women, but it showed significant increases only at 10 minutes after fatigue in men. 3. In the comparison of MVC among the treatment groups, it showed significant differences among the groups at 10 minutes after fatigue. 4. In the comparison of changes in MVC among the time frames for each group, the rest group showed significant differences in MVC between 0 and 10 minutes after fatigue and between 20 and 30 minutes after fatigue. The massage group showed significant differences in MVC between 0 and 10 minutes after fatigue and between 10 and 20 minutes after fatigue. The stretching group showed a significant difference in MVC between 10 and 20 minutes after fatigue and between 20 and 30 minutes after fatigue.