Evidence that peaks in EMG averages can sometimes be caused by inhibition of motoneurons

1. It has been reported that an excitatory response occurs before strong inhibition in masticatory muscles. We tested the hypothesis that this small monopolar wave in the EMG, called by us the early exteroceptive component (EEC), is in fact the first response to inhibition. 2. A mapping of the electrical activity of the masseter muscle was performed using a 3 x 4 matrix of surface electrodes with reference to the back of the neck. Subjects sat with the jaw closing muscles relaxed or contracting at approximately 75% of the maximum voluntary level. The chin was tapped to evoke a jaw jerk reflex and the EEC was elicited by electrical stimulation to the palate. 3. In addition, bipolar EMGs and jaw position were recorded at minimal bite forces and at contraction levels of 5, 10, 15, or 20 N. 4. Data were computer average, with and without rectification, for 32 stimuli. 5. The EEC [latency 12.1 +/- 1.0 (SD)ms] was found to have the same polarity, shape, and duration as the repolarizing wave of the stretch reflex. 6. After electrical stimulation, an increase of bite force was never observed during or immediately after the EEC. Instead, bite force began to decrease 5-7 ms after the onset of the EEC. 7. The amplitude of the EECs never exceeded the level of the peaks in the preceding background EMG, even when the left and right palatal electrodes were stimulated simultaneously at high intensity.(ABSTRACT TRUNCATED AT 250 WORDS)

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Effect of Neuromuscular Electrical Stimulation Combined with Traditional Dysphagia Rehabilitation on Masseter Muscle Thickness and Bite Force in Stroke with Dysphagia Patient

Journal of international academy of physical therapy research ◽

10.20540/jiaptr.2021.12.1.2365 ◽

2021 ◽

Vol 12 (2) ◽

pp. 2365-2369

Author(s):

Myunglyeol Lee ◽

Kuija Lee ◽

Jinuk Kim

Keyword(s):

Electrical Stimulation ◽

Masseter Muscle ◽

Neuromuscular Electrical Stimulation ◽

Muscle Thickness ◽

Bite Force ◽

Dysphagia Rehabilitation

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Effects of Intense Chewing Exercises on the Masticatory Sensory-Motor System

Journal of Dental Research ◽

10.1177/0022034509338573 ◽

2009 ◽

Vol 88 (7) ◽

pp. 658-662 ◽

Cited By ~ 17

Author(s):

M. Koutris ◽

F. Lobbezoo ◽

M. Naeije ◽

K. Wang ◽

P. Svensson ◽

...

Keyword(s):

Masseter Muscle ◽

Stretch Reflex ◽

Myofascial Pain ◽

Masticatory Muscles ◽

Reflex Amplitude ◽

Pain Thresholds ◽

Pressure Pain ◽

Pain Scores ◽

Pressure Pain Thresholds ◽

Exercise Muscle

Nociceptive substances, injected into the masseter muscle, induce pain and facilitate the jaw-stretch reflex. It is hypothesized that intense chewing would provoke similar effects. Fourteen men performed 20 bouts of 5-minute chewing. After each bout, 20 min and 24 hrs after the exercise, muscle fatigue and pain scores and the normalized reflex amplitude from the left masseter muscle were recorded. Before, 20 min, and 24 hrs after the exercise, signs of temporomandibular disorders and pressure-pain thresholds of the masticatory muscles were also recorded. Fatigue and pain scores had increased during the exercise (P < 0.001), but the reflex amplitude did not (P = 0.123). Twenty minutes after the exercises, 12 participants showed signs of myofascial pain or arthralgia. Pressure-pain thresholds were decreased after 20 min (P = 0.009) and 24 hrs (P = 0.049). Intense chewing can induce fatigue, pain, and decreased pressure-pain thresholds in the masticatory muscles, without concomitant changes in the jaw-stretch reflex amplitude.

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Effect of Neuromuscular Electrical Stimulation on Masseter Muscle Thickness and Maximal Bite Force among Healthy Community-Dwelling Persons Aged 65 Years and Older: A Randomized, Double Blind, Placebo-Controlled Study

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph17113783 ◽

2020 ◽

Vol 17 (11) ◽

pp. 3783

Author(s):

Moon-Young Chang ◽

Gihyoun Lee ◽

Young-Jin Jung ◽

Ji-Su Park

Keyword(s):

Electrical Stimulation ◽

Placebo Group ◽

Masseter Muscle ◽

Neuromuscular Electrical Stimulation ◽

Muscle Thickness ◽

Bite Force ◽

Community Dwelling ◽

Controlled Study ◽

Healthy Community ◽

Experimental Group

Aim: This study investigated the effect of neuromuscular electrical stimulation (NMES) on masseter muscle thickness and maximal bite force among healthy community-dwelling elderly persons older than 65 years. Materials and methods: A total of 40 participants were randomly assigned to the experimental and placebo groups. In the experimental group, NMES was applied to both masseter muscles, and electrical signals were gradually increased until the participants felt a grabbing sensation (range 6.0–7.5 mA) in the masseter muscle. The placebo group, in contrast, underwent NMES in the same manner and procedure as the experimental group with less electrical intensity (0.5 mA). All interventions were administered five times a week for six weeks, 20 min per day. The outcomes were masseter muscle thickness assessed using ultrasound and maximal bite force using a bite force meter. The level of significance was set as p < 0.05. Results: The experimental group showed a significant increase in both masseter muscle thickness and maximal bite force as compared with the placebo group (p = 0.002 and 0.019, respectively). Moreover, the degree of change in the masseter muscle thickness and maximal bite force significantly increased in the experimental and placebo groups (p < 0.001, both). Conclusions: This study demonstrated that NMES could be an effective modality for increasing masseter muscle thickness and maximal bite force in healthy older adults.

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Effects of Neuromuscular Electrical Stimulation Synchronized with Chewing Exercises on Bite Force and Masseter Muscle Thickness in Community-Dwelling Older Adults in South Korea: A Randomized Controlled Trial

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph17134902 ◽

2020 ◽

Vol 17 (13) ◽

pp. 4902

Author(s):

Ji-Su Park ◽

Young-Jin Jung ◽

Min-Ji Kim

Keyword(s):

Older Adults ◽

Electrical Stimulation ◽

Masseter Muscle ◽

Neuromuscular Electrical Stimulation ◽

Muscle Thickness ◽

Bite Force ◽

Community Dwelling ◽

Control Group ◽

Community Dwelling Older Adults ◽

Experimental Group

This study is aimed at investigating the effects of synchronized neuromuscular electrical stimulation (NMES) and chewing exercises on bite force and the masseter muscle thickness in community-dwelling older adults. Material and methods: Forty older adults were enrolled in South Korea and randomly assigned to either an experimental or control group. The experimental group performed chewing exercises using the No-Sick Exerciser equipment synchronized with NMES applied to the bilateral masseter muscles, while the control group performed only chewing exercises. Both groups received interventions for 20 min/day, 5 days/week, for 6 weeks. Bite force was measured using the OCCLUZER device, and masseter muscle thickness was measured using a portable ultrasound. Results: Both groups showed a significant increase in bite force and masseter muscle thickness compared to baseline measurements (p < 0.05). The experimental group showed a significantly higher increase in bite force and masseter muscle thickness than the control group after combined intervention (p < 0.05). Conclusion: This study demonstrates that NMES synchronized with chewing exercises is more efficient in increasing bite force and masseter muscle thickness than chewing exercises alone in community-dwelling older adults.

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The Relationship between Jaw Position and Masticatory Muscles' EMG Activity Based on Three Dimensional Bite Force Registration.

Nihon Hotetsu Shika Gakkai Zasshi ◽

10.2186/jjps.40.357 ◽

1996 ◽

Vol 40 (2) ◽

pp. 357-369 ◽

Cited By ~ 1

Author(s):

Tetsuo Kawata

Keyword(s):

Three Dimensional ◽

Masticatory Muscles ◽

Bite Force ◽

Emg Activity ◽

Jaw Position ◽

The Relationship

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Activities of masseteric nerve and stretch reflex elicited by extension of the frog masseter muscle.

Japanese Journal of Oral Biology ◽

10.2330/joralbiosci1965.29.397 ◽

1987 ◽

Vol 29 (4) ◽

pp. 397-407 ◽

Cited By ~ 1

Author(s):

Kouichi Shiozawa ◽

Yasutake Saeki ◽

Keiji Yanagisawa

Keyword(s):

Masseter Muscle ◽

Stretch Reflex ◽

Masseteric Nerve

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Reflex responses of motor units in human masseter muscle to electrical stimulation of the lip

Experimental Brain Research ◽

10.1007/bf00236305 ◽

1987 ◽

Vol 65 (2) ◽

Cited By ~ 36

Author(s):

T.S. Miles ◽

K.S. T�rker ◽

M.A. Nordstrom

Keyword(s):

Electrical Stimulation ◽

Masseter Muscle ◽

Motor Units ◽

Reflex Responses ◽

Stimulation Of

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Jaw Reflexes Evoked by Mechanical Stimulation of Teeth in Humans

Journal of Neurophysiology ◽

10.1152/jn.1999.81.5.2156 ◽

1999 ◽

Vol 81 (5) ◽

pp. 2156-2163 ◽

Cited By ~ 20

Author(s):

J. Yang ◽

K. S. Türker

Keyword(s):

Mechanical Stimulation ◽

Masseter Muscle ◽

Response Pattern ◽

Bite Force ◽

Reflex Response ◽

Incisor Tooth ◽

Jaw Muscles ◽

Reflex Responses ◽

Closing Force ◽

Stimulation Of

Jaw reflexes evoked by mechanical stimulation of teeth in humans. The reflex response of jaw muscles to mechanical stimulation of an upper incisor tooth was investigated using the surface electromyogram (SEMG) of the masseter muscle and the bite force. With a slowly rising stimulus, the reflex response obtained on the masseter SEMG showed three different patterns of reflex responses; sole excitation, sole inhibition, and inhibition followed by excitation. Simultaneously recorded bite force, however, exhibited mainly one reflex response pattern, a decrease followed by an increase in the net closing force. A rapidly rising stimulus also induced several different patterns of reflex responses in the masseter SEMG. When the simultaneously recorded bite force was analyzed, however, there was only one reflex response pattern, a decrease in the net closing force. Therefore, the reflex change in the masseter muscle is not a good representative of the net reflex response of all jaw muscles to mechanical tooth stimulation. The net response is best expressed by the averaged bite force. The averaged bite force records showed that when the stimulus force was developing rapidly, the periodontal reflex could reduce the bite force and hence protect the teeth and supporting tissues from damaging forces. It also can increase the bite force; this might help keep food between the teeth if the change in force rate is slow, especially when the initial bite force is low.

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ANALYSIS OF THE DYNAMICS OF FUNCTIONAL OCCLUSION INDICATORS IN THE CONSTRUCTION OF OCCLUSION SURFACES OF ORTHOPEDIC STRUCTURES

Wiadomości Lekarskie ◽

10.36740/wlek202012117 ◽

2020 ◽

Vol 73 (12) ◽

pp. 2651-2656

Author(s):

Svitlana P. Yarova ◽

Sergii O. Turchenenko ◽

Iryna M. Tkachenko ◽

Yuriy Yu. Yarov

Keyword(s):

Functional Condition ◽

Masticatory Muscles ◽

Main Group ◽

Suggested Method ◽

Control Group ◽

Orthopedic Treatment ◽

Functional Parameters ◽

Occlusal Surfaces ◽

Left And Right ◽

And Control

The aim: Is to evaluate the effectiveness of the proposed method of constructing occlusal surfaces of orthopedic structures by monitoring the dynamics of functional indicators of occlusion and the functional condition of the masticatory muscles. Materials and methods: The object of the study was made up by 64 patients with included defects of the dentition of the 3rd class according to Kennedy. Patients were divided into two equal groups – the main group (patients were treated by using the suggested method of construction of occlusal surfaces of orthopedic structures) and control (dentition defects were replaced according to the traditional protocol). Results: The results of evaluating the effectiveness of the proposed method showed that the index of symmetry of the anterior bundles of the temporal muscles dropped by 18.5%, the index of symmetry of the masticatory muscles reduced by 22%, the torque of the mandible reduced by 32%, the index of stabilizing occlusal – by 27%, relative efforts of balance disturbance for more than 10 % regarding the left and right reduced by a factor of 4.4, the rate of opening time was 1.5 times higher than before, the rate of time of opening of the jaws – 1.8 times. Conclusions: The use of the suggested method of orthopedic treatment with temporary structures leads to probable changes in the studied functional parameters in comparison with the control group (p <0,05).

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