Article

Modulation of H reflex of pretibial and soleus muscles during mastication in humans

Authors:
  • Meikai University School of Dentistry
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Abstract

A previous study in our laboratory demonstrated that the soleus H reflex was facilitated during mastication in humans. In the present study, we investigated whether there was any modulation of the magnitude of the pretibial H reflex during mastication in five healthy adult volunteers. The pretibial H reflex was significantly facilitated during mastication, and there was no significant difference in the facilitation between jaw-closing and jaw-opening phases; that is, the gain of the H reflex was modulated tonically but not in a phase-dependent manner during mastication. Furthermore, in the same subjects, we confirmed that the soleus H reflex was facilitated during mastication. Based on our findings, we conclude that the H reflexes in both the pretibial and soleus muscles undergo a nonreciprocal facilitation during mastication. It is suggested that mastication contributes to stabilization of postural stance in humans. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1142–1148, 2001

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... Previous studies have analyzed the relationships between the mandibular position and body posture [11,12]. Further studies have discussed relationships between mastication and the static [13,14] and dynamic [7] balance of body posture, leg muscle activity [15], neck muscle activity [16], head position [17], and upper half of body [18]. ...
... Yagi et al. [26] reported that the leg muscles, which directly regulate the movement of the ankle joint, and the dorsal neck muscles, which change the static equilibrium through the central nervous system, are important for maintaining the standing posture. Takahashi et al. [15] indicated that the H reflexes in both the pretibial and soleus muscles undergo a nonreciprocal facilitation during mastication. Takada et al. [28] found the increase in amplitude of the pretibial and soleus H reflex showed a positive correlation with the strength of teeth clenching. ...
... 5, 6 and 8). Based on the previous reports [15,26,[28][29][30], one can infer that when the subjects masticated chewing gum, the occlusal force might have been larger compared to it in centric occlusion, and the pattern of the masticatory movement path had the stability of the path and rhythm and a superior masticatory function. Moreover, the present results showed the possibility that the peripheral inputs from each organ in the stomatognathic system during mastication may have strongly affected the muscles, pretibial and soleus muscle, and the upper central nervous system, which regulate the craniocervical muscles, as the positive feedback control to maintain and stabilize the standing posture. ...
Article
Introduction Mastication involves complex tongue movements, coordination of lip, and cheek movements and is associated with head movement to facilitate the intraoral transport of food from ingesting to swallowing; it affects many functions of the whole body. However, studies to evaluate the relationship between masticatory movements and the body posture are still lacking to our knowledge. The purpose of this study was to characterize the effects of masticatory movements on the head, trunk, and body sway during the standing position. Methodology A total of 30 healthy subjects were evaluated. The MatScanTM system was used to analyze changes in body posture (center of foot pressure: COP) and the 3-dimensional motion analysis system was used to analyze changes in the head and trunk postures while subjects remained in the standing position with the rest position, centric occlusion, and masticating chewing gum. Results The total trajectory length of COP and head and trunk sways during masticating chewing gum were significantly shorter and smaller respectively than it was in the rest position and centric occlusion (p<0.016). COP area during masticating chewing gum was significantly smaller than it was in the 2 mandibular positions (p<0.016). Conclusion Masticatory movements positively affect the stability of the head, trunk, and body sways and enhance the postural stability during the standing position.
... Further studies [14][15][16][17][18][19][20][21] verified the influence of occlusion on head and neck posture and on lumbar spinae and leg posture. [22][23][24] In recent years, surface electromyography (sEMG) has been largely utilized for testing the masticatory muscles, [15][16][17][18]25,[27][28][29] becoming the well-established gold standard for checking the tonicity and symmetry of these muscles. 26 The technique has been shown to be a useful method to assess the activity of other muscles in the body. ...
... sternocleidomastoid, had a strict prevalence vs. the other paired muscles in the improvement of sEMG, following occlusal repositioning. These data confirm the observations of other studies, 2,18,22,32,40 that the muscles involved in dental occlusion may influence other muscle activity, not because of a simple spatial correlation, but rather because of more complex neuro-mediated reflexes. ...
... The authors in the current study believe that the balancing rate parameter must be even more extensively related to subtle neuro-mediated mechanisms, which act as supreme coordination controllers, based on several studies on the relationship between postural instability and silent periods of the soleus and gastrocnemious muscles. 22,41 Further studies on animal models may be useful in demonstrating whether such phenomenon could depend on the upright posture of humans. ...
Article
Full-text available
The influence between dental occlusion and body posture has been discussed in the past ten years by several authors with controversial conclusions. The objective of this study was to access, using surface electromyography (EMG), the rest activity of paired sternocleidomastoids, erectors spinae at L4 level, and soleus muscles in a group of 24 volunteer subjects (12 males, 12 females, aged 23-25 yrs) affected by sub-clinical dental malocclusions in different situations of dental occlusion. The subjects' occlusion was balanced (neuromuscularly) (registered on an acrylic wafer). Rest activity was assessed using the sEMG. The measurements were achieved on subjects while standing barefooted, before (Test 1), and 15 minutes after they wore the acrylic wafer (Test 2). The result was a significant reduction of the mean voltage for each muscle. Paired muscles were registered and the balancing rate between right and left muscles showed improvement for all the paired muscles (Wilcoxon test p < 0.05). No significant difference was noted in the relaxation and balancing rates between the muscles tested. The data confirmed a beneficial effect of balancing the occlusion with an acrylic wafer on the following paired postural muscles: sternocleidomostoid, erector spinae, and soleus.
... It has been reported that mastication can physiologically improve the cerebral blood flow [4], 204 and improve cognition, mood, and relieve stress by relieving anxiety [5,6]. Studies have also been discussed relationships between mastication and leg muscle activity [7], neck muscle activity [8], head posture [9], upper body movement [10]. ...
... There are reports in the literature that mastication facilitates H reflex in both the pretibial and soleus muscles [7] and that stimulation of the vestibular system by changing head position has a descending influence on the triceps surae muscle and the soleus muscle, both antigravity muscles [17]. Based on these previous reports, one can infer that when subjects masticated gummy jelly compared to when they maintained their mandibles in rest position and centric occlusion, the facilitation of H reflex associated with mastication and changes in head posture due to the coordinated head movements in response to mandibular movements during mastication may have impacted the activity of the lower extremity muscles, the pretibial and soleus muscles and consequently, the displacement of COFP may have been larger compared to that during rest position and centric occlusion. ...
... They showed that the amplitude of the reflex increased as the strength of teeth clenching also increased and this facilitation was maintained till the end of the clenching. Nonetheless, Takahashi et al. (2001) demonstrated no difference between clenching and opening of the jaw with regard to modulation of soleus H-reflex while chewing. And recently, Allen (2019) found a significant increase in vertical jump height and handgrip strength following maximal jaw opening. ...
... These facilitation effects may explain the phenomenon of concurrent activation potentiation discussed above. Indeed, given the results of Takahashi et al. (2001) and Allen (2019) it is possible that jaw stretching may have similar effects. What is common to both stretching and clenching is the activation of proprioceptive afferents to the trigeminal mesencephalic nucleus located in the pons (Lazarov, 2000). ...
Article
The use of oral appliances is considered effective in improving sport performance. Jaw clenching or stretching,improved breathing or positioning of the jaw have been proposed to explain the improvement. In this study, we reported the effects of regularly practiced mandibular stretching at submaximal opening of the jaw in Crossfit athletes. Seventeen test subjects undergoing mandibular stretching (MS) showed significantly reduced (p < 0.001) performance time in a high-intensity workout measured before and after seven days of 10-minutes stretching practiced twice daily, while no improvement was observed in control subjects who did not perform the stretching. Additionally, blood lactate levels appeared to recover more quickly in MS subjects. Crossfit is a type of training regimen that pushes the limits of bodily recovery processes. Jaw stretching, eliciting the trigeminocardiac reflex (a reflex decrease in heart rate and blood pressure following trigeminal stimulation) and central oxygen-conserving mechanisms could help relieve post-training stress and improve training recovery.
... In addition, they suggested that peripheral factors, including afferent sensory inputs from periodontal mechanoreceptors and central commands for clenching, play an important role in facilitation of the soleus H-reflex. Since then, a number of studies have demonstrated that voluntary teeth clenching facilitates human lower limb motor function (Takada et al., 2000;Takahashi et al., 2001;Sugawara and Kasai, 2002). Takahashi et al. (2003) investigated whether there was any modulation of the H-reflex in the upper limbs during voluntary teeth clenching, using the H-reflex of the flexor carpi radialis (FCR) and the extensor carpi radialis (ECR) muscles. ...
... The facilitation of stretch reflexes in the extremities by the contraction of remote muscles is a well-known phenomenon in neurology. As mentioned in the introduction, the H-reflex of muscles in the upper and lower limbs is facilitated by teeth clenching (Miyahara et al., 1996;Takada et al., 2000;Takahashi et al., 2001Takahashi et al., , 2003. The neuronal mechanisms underlying the facilitation of stretch reflexes by contraction of remote muscles have not yet been elucidated. ...
Article
We assessed the effect of teeth clenching on handgrip force behaviorally, and investigated cortical activity during the occurrence of facilitatory effects using functional magnetic resonance imaging (fMRI). Twenty-three participants were assessed as to whether they had habitual teeth clenching during maximal voluntary contraction (MVC) exertion, and 21 of them were identified to have such a habit. For those participants, behavioral testing showed that MVC with clenching was greater compared with without clenching (approximately 108% greater on average). Next, cortical activity was measured under gripping with clenching (GwC), gripping without clenching (GwoC), and teeth clenching (C) conditions. We found that the activity of the hand region in primary motor cortex (M1), cingulate motor area/supplementary motor area (CMA/SMA) and anterior cerebellum (AC) was greater in contrast of GwC vs. (GwoC+C). Furthermore, significant correlation was observed between the increasing ratio of the handgrip force and the % signal change in the hand region of M1 and AC, but not in CMA/SMA. These results suggest that the activation in the hand region of M1 and AC may facilitate the spinal motoneurons, and the activation in the hand region in M1 by clenching may be due to a signal from CMA/SMA.
... Mastication may contribute to modulation of the H reflex of pretibial and soleus muscles in humans. It has been confirmed that the H reflexes in both the pretibial and soleus muscles undergo a nonreciprocal facilitation during mastication [12]. Furthermore, modulation of the H reflex of pretibial and soleus muscles during mastication in humans has been reported [12]. ...
... It has been confirmed that the H reflexes in both the pretibial and soleus muscles undergo a nonreciprocal facilitation during mastication [12]. Furthermore, modulation of the H reflex of pretibial and soleus muscles during mastication in humans has been reported [12]. The other effects of chewing gum will be on the central nerve system. ...
Article
The chewing gum indirectly affects postural control by influencing vestibular function to stabilize posture during upright standing. This study aimed to evaluate the effect of chewing gum on static posturography in patients. The subjects were 26 patients with chronic balance disorders. The subjects were instructed to stand as stably as possible on the force platform. The recording was conducted four times. For the first evaluation, postural sway was measured during motionless standing. Two weeks after the recording, the postural sway was recorded again as a second evaluation. Thereafter, the subjects were instructed to chew gum for 3 min. The third evaluation was conducted while the subjects continued to chew gum. Then 1 h after the subject had stopped chewing gum, a fourth evaluation was obtained. The total path length (LNG) and rectangle area (REC) were analyzed. We found that postural stability tended to improve while the subjects masticated gum. Both LNG and REC were significantly improved while the subjects chewed gum with their eyes closed. In patients without canal paralysis (CP), the measurements of LNG with eyes closed and REC with eyes open were significantly decreased while masticating gum. In patients with CP, the REC, but not LNG, was significantly decreased while masticating gum both with eyes open and eyes closed.
... It has been reported that masticatory movements can physiologically improve the cerebral blood flow [4], and also improve cognition, and mood, and reduce stress by relieving anxiety [5,6]. Further studies have discussed the relationships between masticatory movements and static [7,8] and dynamic [9] balance of body posture, leg muscle activity [10], neck muscle activity [11], head posture [12], and upper body movement [13]. ...
Article
Full-text available
Purpose: To verify the effect of sitting posture with and without sole-ground contact on chewing stability and masticatory performance. Methods: Thirty healthy subjects were evaluated. The Conformat was used to analyze the center of sitting pressure (COSP), and the three-dimensional motion analysis system was used to analyze changes in head and trunk postures while subjects remained in a sitting position with and without sole-ground contact. The parameters of masticatory performance and movement were calculated as follows. For evaluating masticatory performance, the amount of glucose extraction (AGE) during chewing of a gummy jelly was measured. For evaluating masticatory movements, the movement of the mandibular incisal point was recorded using the Motion Visi-Trainer V1, and parameters of the stabilities of movement path and rhythm were calculated. Results: Head and trunk sway values and the displacement of COSP were significantly smaller with sole-ground contact than those without soleground contact. The masticatory movement path with sole-ground contact showed less variation in the opening distance and more stable movement path compared to those without sole-ground contact. The AGE was significantly greater with sole-ground contact than that without sole-ground contact. Conclusion: Sitting posture with and without sole-ground contact affects chewing stability and masticatory performance.
... A growing body of literature suggests that there is a close relationship between the stomatognathic system and balance (10)(11)(12)(13)(14)(15)(16)(17)(18). The underlying mechanisms have not yet been fully understood; however, in various studies (19)(20)(21)(22), it was shown that jaw clenching like the Jendrassik maneuver (23) may lead to increased motor excitability and increased H-reflex responses. In addition, co-contraction behavior of the masticatory and neck muscles occurring as a result of complex neurophysiological interactions (24) may also contribute to improved postural control, for example, via a more stable head or gaze position (25-27). ...
Article
Full-text available
Introduction Good balance is essential for human daily life as it may help to improve the quality of life and reduce the risk of falls and associated injuries. The influence of jaw clenching on balance control has been shown under static and dynamic conditions. Nevertheless, it has not yet been investigated whether the effects are mainly associated with the dual-task situation or are caused by jaw clenching itself. Therefore, this study investigated the effects of jaw clenching on dynamic reactive balance task performance prior to and after 1 week of jaw clenching training. It was hypothesized that jaw clenching has stabilizing effects resulting in a better dynamic reactive balance performance, and these effects are not related to dual-task benefits. Methods A total of 48 physically active and healthy adults (20 women and 28 men) were distributed into three groups, one habitual control group (HAB) and two jaw clenching groups (JAW and INT) that had to clench their jaws during the balance tasks at T1 and T2. One of those two groups, the INT group, additionally practiced the jaw clenching task for 1 week, making it familiar and implicit at T2. The HAB group did not receive any instruction regarding jaw clenching condition. Dynamic reactive balance was assessed using an oscillating platform perturbed in one of four directions in a randomized order. Kinematic and electromyographic (EMG) data were collected using a 3D motion capture system and a wireless EMG system, respectively. Dynamic reactive balance was operationalized by the damping ratio. Furthermore, the range of motion of the center of mass (CoM) in perturbation direction (RoMCoM_AP or RoMCoM_ML), as well as the velocity of CoM (VCoM) in 3D, were analyzed. The mean activity of the muscles relevant to the perturbation direction was calculated to investigate reflex activities. Results The results revealed that jaw clenching had no significant effects on dynamic reactive balance performance or CoM kinematics in any of these three groups, and the automation of jaw clenching in the INT group did not result in a significant change either. However, high learning effects, as revealed by the higher damping ratio values and lower VCoM at T2, were detected for the dynamic reactive balance task even without any deliberate balance training in the intervention phase. In the case of backward perturbation of the platform, the soleus activity in a short latency response phase increased for the JAW group, whereas it decreased for HAB and INT after the intervention. In the case of forward acceleration of the platform, JAW and INT showed a higher tibialis anterior muscle activity level in the medium latency response phase compared to HAB at T1. Discussion Based on these findings, it can be suggested that jaw clenching may lead to some changes in reflex activities. However, the effects are limited to anterior–posterior perturbations of the platform. Nevertheless, high learning effects may have overall overweighed the effects related to jaw clenching. Further studies with balance tasks leading to less learning effects are needed to understand the altered adaptations to a dynamic reactive balance task related to simultaneous jaw clenching. Analysis of muscle coordination (e.g., muscle synergies), instead of individual muscles, as well as other experimental designs in which the information from other sources are reduced (e.g., closed eyes), may also help to reveal jaw clenching effects.
... The Jendrassik maneuver involves clenching the jaw, hooking and interlocking the fingers, then attempting to pull the hands apart while the tendon reflex is invoked. However, Takahashi et al. (2001) demonstrated that there was no difference between jaw clenching and jaw opening in regards to soleus H-reflex modulation. Therefore, maximally opening the jaw may be a viable RVC strategy to produce CAP and enhance muscular force production characteristics. ...
Article
Full-text available
Purpose: The purpose of this study was to examine maximal jaw opening as a strategy to elicit concurrent activation potentiation during countermovement vertical jump performance and bilateral grip strength assessment in both males and females. Methods: Twenty-four males (age 21.25 ± 1.45 years; height 177.64 ± 7.67 cm; mass 83.87 ± 9.08 kg) and 24 females (age 21.38 ± 2.12 years; height 165.84 ± 8.96 cm; mass 66.4 ± 13.42 kg) participated in this investigation. Maximal countermovement jump height was recorded using a Just Jump Mat, and dominant and non-dominant handgrip strength was recorded using a digital hand dynamometer under two experimental conditions: jaw relaxed and jaw maximally opened. Paired-sample t-tests were conducted for each dependent variable of interest to determine the differences between the research conditions. Results: Maximally opening the jaw led to improvements in vertical jump height (p = 0.013, d = 0.225), dominant hand (p = 0.028, d = 0.162), and non-dominant handgrip strength (p = 0.011, d = 0.241) in males, and although these variables were improved in females under the jaw open condition, that improvement did not reach statistical significance (p > 0.05). Conclusion: This study supports maximally opening the jaw as an effective strategy for producing concurrent activation potentiation, particularly in males.
... Previous studies showed that voluntary teeth clenching has facilitatory effects on the excitability of the remote parts of the body such as the upper limbs [19][20][21] and lower limbs. 19,22,23 These findings also suggested that the remote effects of facilitation are given via both cortical and subcortical motor areas. In our results, T2, which related to the subcortical information processing, correlated negatively with the masseter activity in the late 0.5 second. ...
Article
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Objectives/HypothesisWe hypothesized that proprioceptive signals during the oral phase play a pivotal role in the initiation of pharyngeal phase during volitional swallowing. Therefore, we tested if swallowing could be modified by changing the amount of proprioceptive feedback from a number of different receptors while holding a food bolus in the mouth and clenching.Study DesignBasic research.Methods Surface electromyography (sEMG) recordings of the masticatory muscles were obtained during volitional swallowing movements from seven healthy adults with no clinical history of swallowing difficulties. The swallowing procedure involved holding 5 ml of jelly on the tongue before swallowing it completely, according to visual cues on a computer display. Initiation of the swallowing reflex was detected by an anterior shift of the thyroid cartilage using a laser displacement sensor and by submental sEMG signals. To vary the proprioceptive input, the participants were instructed to occlude their teeth at various intensities (weak, intermediate, and strong) while holding the 5-ml jelly bolus on the tongue.ResultsRectified and integrated sEMG (iEMG) signals obtained from the submental area showed two upward deflections. Contractile forces of the masseter muscles showed significant negative values for Pearson correlation coefficient against time intervals from the onset of the second submental iEMG deflection to the onset of the anterior shift of the thyroid cartilage in six of the seven participants (average −0.534, standard deviation 0.176).Conclusion Contractile forces of the masseter muscles during occlusion tended to correlate negatively with electromechanical delays on suprahyoid muscle contraction.Level of EvidenceNA Laryngoscope, 2015
... During standing corrective muscular action is required to counter the periodic destabilization in the form of postural sway. It has been reported that mastication facilitates H reflex in both the pretibial and soleus muscles (Takahashi et al. 2001) and that with jaw clenching, neck and trunk muscles co-contract with jaw muscles (Ehrlich et al. 1999). This shows the functional integration of the head-neck region into the neuromuscular system of the body (Hellmann et al. 2011) contributing in the feedback control mechanism to control the sway during such dynamic conditions (Peterka and Loughlin 2004). ...
Article
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Background and aims: There is an important role of the neck sensory motor system in control of body posture and balance, and it is reasonable to believe that the jaw sensory motor system can directly and indirectly influence the modulation of the postural control system. The purpose of this study was to evaluate possible effects of dynamic jaw position while chewing on the postural control system. Materials and methods: We compared the mean center of gravity (COG) velocity during quite standing on a foam surface with eyes closed during three test conditions: (i) with resting jaw position, (ii) with open jaw position, and (iii) while chewing standard bolus of chewing gum. One hundred and sixteen normal healthy male subjects (average age 31.56 ± 8.51 years; height 170.86 ± 7.26 cm) were recruited for the study. Their COG velocity (deg/s) was measured using the NeuroCom® Balance Master Version 8.5.0 (Clackamas, OR, USA). Statistical analysis: Data was tested by the Friedman test. Results and conclusions: The results show that COG velocity decreased significantly while chewing in comparison to both open and resting jaw position (p < 0.0001). Our finding corroborates previous studies and suggests that the jaw sensory motor system can modulate postural control mechanisms. Gum chewing activity can enhance the postural stability during upright standing on an unstable surface and in the absence of visual input in healthy young adults. Our results should be taken into consideration in treatment and rehabilitation planning for patients with postural instability.
... Similar observations have been made previously for inspiratory movements (Maillard et al., 1983). H-reflex facilitation can occur due to many influences, such as mastication (Takahashi, Ueno, Taniguchi, Ohyama, & Nakamura, 2001) or voluntary jaw clenching (Sugawara & Kasai, 2002). These, as well as our respiratory maneuvers, may be examples of the Jendrassik effect, in which a voluntary muscle contraction causes an increase in amplitude of monosynaptic spinal reflexes (Gregory, Wood, & Proske, 2001). ...
Article
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We compared the effects of laughter and several respiratory movements on spinal motor excitability to unravel their respective influences. We measured H-reflexes in 13 healthy volunteers during 10 different tasks (including laughter, simulated laughter, and various respiratory movements). We compared the percentage that remained of the initial H-reflex during each task with that during a neutral task. H-reflex percentage differed between the neutral task (79.4 AE 16.1%), true laughter (43.7 AE 17.9%), and simulated laughter (66.6 AE 24.3%), and between the two latter tasks. Coughing also resulted in H-reflex suppression, but not as deeply as true laughter. During the other respiratory maneuvers, the H-reflex increased compared to the neutral task. Our finding that true laughter evoked more H-reflex depression than simulated laughter suggests that mirth on its own depresses the H-reflex. This mechanism may also be involved in the pathophysiology of cataplexy, the main symptom of narcolepsy.
... Stimuli (1-millisecond pulse duration) were provided by a Grass S48 stimulator with a SIU5 stimulus isolation unit (Grass), and stimulus timing pulses were digitized concurrently. During all measurements, it was verified that the subject was contracting only the muscles needed for the posture, and the ankle plantar flexors when requested, and that other muscle contractions, such as jaw clenching and the Jendrassik maneuver, known to influence soleus H-reflex amplitude were avoided (36,37). ...
Article
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Soleus Hoffman-reflex (H-reflex) gain was compared at the same background level of electromyographic activity across lying, natural standing, and tandem stance postures, in 12 young and 16 elderly adults. When compared to a lying posture, young adults significantly depressed soleus H-reflex gain when in a natural standing (19% decrease) and a tandem stance position (30% decrease; p <.0125 for both positions). For elderly adults, there was no significant decrease in H-reflex gain while standing naturally, but there was a significant 28% decrease when performing tandem stance (p <.0125). The data indicate that, although the mild motor control challenge of natural standing does not induce a decrease in soleus H-reflex gain in the elderly adults, as it does in young adults, in the more difficult task of tandem stance, soleus H-reflex gain is significantly decreased in both young and elderly adults.
Article
Purpose: The purpose of this study was to test the hypothesis in healthy subjects that masticatory movements affect head and trunk sways, and sitting and foot pressure distributions during sitting position. Methods: A total of 30 healthy male subjects with an average age of 25.3 years (range, 22-32 years) were evaluated. The CONFORMatTM and MatScanTM system were used to analyze changes in sitting pressure distribution (center of sitting pressure: COSP) and changes in foot pressure distribution (center of foot pressure: COFP) respectively, and the 3-dimensional motion analysis system was used to analyze changes in head and trunk postures while subjects remained sitting position with rest position, centric occlusion, and chewing. The total trajectory length of COSP/COFP, COSP/COFP area, and head and trunk sway values were compared between the three conditions to evaluate whether masticatory movement affected the stability of head and trunk sways, and sitting and foot pressure distributions. Results: Total trajectory length of COSP and COSP area during chewing were significantly shorter and smaller respectively than it was in rest position and centric occlusion (p < 0.016). Head sway value during chewing was significantly larger than it was in rest position and centric occlusion (p < 0.016). Conclusion: Masticatory movements affect sitting pressure distribution and head movements during sitting position.
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There appears to be much confusion or misinformation worldwide regarding mouthguards and their use in sports. In an effort to clarify where the international dental community stands on mouthguards and mouthguard research, the workshop looked at some important questions. The goal is to one day formulate consensus statements related to these questions, which will be based on current scientific evidence-based research, to motivate the international community of the importance of dentally fitted laminated mouthguards and the wearing of them by athletes of all sports. There are only five sports in the USA that require the use of mouthguards. If through workshops such as this, the importance of wearing dentally fitted laminated mouthguards can be demonstrated, then more sports may require their athletes to wear them. This article is protected by copyright. All rights reserved.
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軟らかくて咀嚼回数が少ないファーストフードや健康補助食品の多量摂取,朝食の欠食などによる不十分な咀嚼は,激変した社会環境を背景として健康に多大な影響を及ぼしている.一方,近年の研究では,食の文化に基づいた歯応えと風味がある食物の十分な咀嚼は,心身の成長の促進,脳の活性化とリラックス作用,食物の発がん物質の発がん性の減弱,活性酸素の消去,肥満の抑制,糖尿病治療効果の向上,運動機能の向上,骨粗鬆化の抑制,脳の損傷や老化のリハビリテーション効果などにつながることが確認または示唆されている.また,この前提条件として,健全な咬合の必要性が強調されている.今後の健康,医療,福祉を展望すると,歯科臨床が主な目的とする咀嚼機能の回復とその維持は不可欠であり,それを標榜してきた日本補綴歯科学会には,重大な責務があるといえよう.具体的に,科学的根拠に基づいた行政施策が実施されるためには,咀嚼機能の診断の確立とその呈示とともに,医学,栄養学,薬学,理工学などとの密に連携した研究と臨床の推進が必須であり,特に広範な領域を専門とする日本補綴歯科学会の担う役割は重大である.
Article
Previous research has shown that mastication reduces shifts in the center of gravity of persons standing still. The present research was conducted to determine whether mastication improves reactive balance in the standing position in response to unanticipated external disturbances. The subjects were 32 healthy male adults (mean age 21.1 years, standard deviation (SD) 0.7 years). Latency data determined with the Motor Control Test of Computerized Dynamic Posturography (CDP) were compared for the three conditions of mastication status, the direction of translation, and the magnitude of translation, using three-way repeated measures ANOVA and lower-order ANOVA with the three conditions separated. Latency was significantly shorter with mastication than with the lower jaw relaxed (P < 0.00001). Mastication alone, however, cannot be considered significant because of the complex interactions involved among the three conditions. Mastication increases not only static balance but also reactive balance in response to unanticipated external disturbances. Gum chewing may therefore reduce falls among elderly persons with impaired balance.
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Hemiplegic patients often exhibit a characteristic condition called Wernicke-Mann contracture. Therefore, the occlusal pattern in hemiplegic patients is considered to be adapted to stress because of this characteristic limb position. We created a sham Wernicke-Mann contracture in healthy individuals using hemiplegia simulator equipment and compared the functional occlusion in this position with that in the normal state to evaluate dynamic adaptive responses. Wernicke-Mann contracture was simulated using a device to create sham hemiplegia (Manabi-tai, Hemiplegia Experiencing Set; Tokushu-iryo, Inc.). In addition to the measurement of the occlusal force using Dental Prescale(®) and Occluzer(®), the occlusion was evaluated using an electromyogram and stabilometer. There was a significant difference in the occlusal force between the normal state and during simulated hemiplegia. The surface electromyo-potential of the masseter muscle showed significantly higher values during simulated hemiplegia. It is significantly higher during simulated hemiplegia than in the normal state on the paralysed side, but not for the normal state on the non-paralysed side. The position and velocity vectors changed in the antero-posterior direction in the normal state but in the lateral direction during simulated hemiplegia. The hemiplegia simulator equipment is useful for research on hemiplegia, and that the occlusal balance is disturbed in the posture characteristic of hemiplegia.
Article
The purpose of this study was to investigate the effect of masticating chewing gum on postural stability during upright standing. To address this issue, 12 healthy subjects performed quiet standing on a force platform for the posturography study. The subjects were instructed to stand as stable as possible on the force platform in order to record the trajectory of the center-of-pressure (COP). After measuring the postural sway in the initial condition (pre-condition), the subjects were asked to stand while masticating chewing gum (gum-condition). Following the gum-condition, quiet standing without mastication was evaluated (post-condition) to ensure the effect of masticating chewing gum on postural stability. The trajectory and velocity of the COP were analyzed for each condition. We found that the postural stability tended to enhance during mastication of chewing gum. The rectangle area of the COP trajectory significantly diminished in the gum-condition and significantly enlarged in the post-condition. A similar effect was observed in the maximum velocity and standard deviation (SD) of the fore-aft amplitude of the COP trajectory. The values were significantly smaller in the gum-condition compared to those in the post-condition. These findings suggest that mastication of chewing gum affects the postural control by enhancing the postural stability during upright standing.
Article
In order to examine the effects of remote facilitation on cortical and spinal sites, we recorded motor evoked potentials (MEPs) and H-reflexes from the flexor carpi radialis muscle of 13 healthy subjects. The H-reflex was used to assess excitability changes at the spinal level, while the MEP following transcranial magnetic stimulation was used to study excitability changes at the cortical level. We induced remote facilitation by means of voluntary teeth clenching (VTC), the so-called Jendrassik maneuver, because this procedure is known to be effective and reliable. Although the facilitation induced by VTC was observed in both evoked potentials (i.e., H-reflex and MEP), which is consistent with previous reports, MEP onset latencies were shortened by VTC in proportion to an increased MEP amplitude, whereas the latencies of the H-reflex were not. Furthermore, statistically significant relationships between MEP latencies and amplitudes were observed in all subjects, whereas no such relationships were observed for the H-reflex. On the basis of these results, two neural pathways are presumed: one involving a release of pre-synaptic inhibition at the spinal level and the other involving an unmasking of lateral excitatory projections at the cortical level.
Article
We studied remote effects of teeth clenching on motor cortical and spinal cord excitability using transcranial magnetic stimulation (TMS), brainstem electrical stimulation (BES), and ulnar nerve stimulation (F-wave) in eight normal volunteers. The TMS, BES, and ulnar nerve stimulation at the wrist were given at different intervals (0-200 ms) after the onset of masseter contraction. Surface electromyographic responses were recorded from the first dorsal interosseous muscle. Responses at different intervals were compared with the response elicited when the subject made no teeth clenching (control response). In TMS, conditioned responses (during teeth clenching) were significantly larger than the control at all intervals. In contrast, in BES and F-waves, conditioned responses were not larger than the control at an early phase (intervals shorter than 50 ms), whereas they were larger than the control at later intervals (longer than 50 ms). These results suggest that facilitation occurs in the hand motor area at the early phase of teeth clenching, and spinal facilitation dominates at its late phase. This time course of facilitation may indicate that the motor cortex must regulate hand muscles finely at the early phase of teeth clenching, and spinal cord may stabilize them firmly at the late phase. The excitability changes of the hand motor area may be in parallel with that of the masseter motor area which reflects the pattern of masseter contraction when the subject activates the masseter muscle phasically at the early phase and sustains that contraction at the late phase.
Article
We compared the effects of laughter and several respiratory movements on spinal motor excitability to unravel their respective influences. We measured H-reflexes in 13 healthy volunteers during 10 different tasks (including laughter, simulated laughter, and various respiratory movements). We compared the percentage that remained of the initial H-reflex during each task with that during a neutral task. H-reflex percentage differed between the neutral task (79.4 +/- 16.1%), true laughter (43.7 +/- 17.9%), and simulated laughter (66.6 +/- 24.3%), and between the two latter tasks. Coughing also resulted in H-reflex suppression, but not as deeply as true laughter. During the other respiratory maneuvers, the H-reflex increased compared to the neutral task. Our finding that true laughter evoked more H-reflex depression than simulated laughter suggests that mirth on its own depresses the H-reflex. This mechanism may also be involved in the pathophysiology of cataplexy, the main symptom of narcolepsy.
Article
Recurrent inhibition in the spinal cord has been suggested to serve as a variable gain regulator to allow for optimal muscle force control, to influence alpha-motoneuron firing rate, and to contribute to task related motor synergies between muscles at the same or different joints. The purpose of this study was to examine the resting recurrent inhibition levels in the soleus motoneuron pool of 20 elderly and 21 young adult subjects. To assess recurrent inhibition, a conditioning electrical stimulus was used to activate group Ia afferent fibers and elicit a reflex response in some of the a-motoneurons innervating the soleus muscle; producing both activation of Renshaw interneurons excited by those involved soleus a-motoneurons via a recurrent branch of the a-motoneuron axon, and an H-reflex response in the soleus muscle. A H' test reflex elicited by a successive supramaximal stimulus to the same nerve 10 ms after the conditioning stimulus evaluated the resulting inhibitory effect. There was no difference in the H' test reflex amplitude when comparing the young and elderly adult subjects. This result was found following two different methods employed to control for a possible effect on the H' test reflex amplitude of a smaller maximum H-reflex amplitude in the elderly subjects. These results indicate that the level of recurrent inhibition in the motoneuron pool of the resting soleus muscles of the young and elderly adults examined was not significantly different.
Article
The aim of the present study was to investigate effects of voluntary teeth clenching (VTC) on motor evoked potentials (MEPs) from the first dorsal interosseous (FDI) muscle to transcranial magnetic stimulation (TMS) by different oriented currents (anterior-medially (AM), posterior-laterally (PL)) of the human motor cortex. In active FDI, VTC enhanced MEP responses induced by AM directed current but reduced these responses induced by PL. In relaxed FDI, VTC enhanced MEP responses by AM but had no significant effects on those by PL. Thus, the results suggest that any components produced by AM directed current were enhanced, whereas those by PL directed currents were not affected or reduced. The present evidence indicates that I-waves recorded at the same latency were not completely the same between those produced by AM and PL directed currents. Because VTC had no influence on responses to brainstem electrical stimulation (BES) or F-waves just after the onset of teeth clenching [T. Furubayashi, K. Sugawara, T. Kasai, A. Hayashi, R. Hanajima, Y. Shiio, N.K. Iwara, Y. Ugawa, Remote effects of self-paced teeth clenching on the excitability of hand motor area, Exp. Brain Res., 148 (2003) 261-265], these modulatory effects on MEPs to both AM and PL directed currents must be due to changes of the motor cortical excitability. Thus, we conclude that VTC affects the motor cortical circuits activated by PL and AM directed currents differentially; it facilitates the one and inhibits the other. This is the first demonstration of opposite effects of the same maneuver on MEP responses elicited by AM and PL directed currents.
Article
To investigate whether the early effects of voluntary teeth clenching (VTC) among the first dorsal interosseous (FDI), abductor digiti minimi (ADM), and abductor pollicis brevis (APB) muscles are differently modulated depending on their muscle properties, we examined the responses of motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation with selected current directions and by brainstem magnetic stimulation (BMS). Although MEP responses with anterior-medially current direction (preferentially elicited I1-waves) were facilitated in all three muscles, those responses with posterior-laterally current direction (preferentially elicited I3-waves) were different among FDI, ADM, and APB muscles. That is, MEP responses in FDI and APB muscles were significantly reduced, whereas those responses in ADM muscle were not significantly reduced. Further, inhibitory effects of VTC in FDI muscle were more potent than those in ADM or APB muscles. On the other hand, the responses to BMS were unchanged by VTC in all three muscles, suggesting that the modulations of MEP were attributed to the cortical origin. On the basis of our previous findings that the inhibitory connections in FDI muscle are more potent than those in ADM muscle (Takahashi et al. in Clin Neurophysiol 116:2757-2764, 2005), the cortical effects of VTC among three hand muscles are differently modulated, depending on muscle properties, presumably the extents of inhibitory connections to corticospinal tract neurons. Considering that the functional capacity in FDI muscle is higher than that in ADM or APB muscles, the cortical inhibitory effect of VTC might contribute to the sophisticated regulation of the motor outputs even during VTC.
Article
Enhancing the acute quality of the resistance training stimulus is the goal of many research and applied professionals. To that end, many methods have been proposed and a variety of training strategies and ergogenic supplements have been investigated. Postactivation potentiation is one phenomenon that has been frequently examined, offering some promise in this regard. Though never previously applied in the strength and conditioning profession, dental research on jaw clenching, studies examining the Jendrassik maneuver and remote voluntary contractions and research on motor overflow together make a compelling case for the existence of a concurrent activation potentiation phenomenon and the acute ergogenic advantage associated with the simultaneous activation of muscles other than the prime mover or synergists. Evidence demonstrates that this advantage is accrued via activation of the H reflex and through cortical overflow. Ultimately, through research and practical application, athletes may be taught to optimize the type, timing, and magnitude of remote muscle actions in order to gain an ergogenic advantage and increase the acute response of the prime movers. This strategy may be especially useful during the most difficult portion of a resistance training repetition and during the most difficult repetitions of a resistance training set.
Article
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The facilitating effect of the Jendrassik manoeuvre on monosynaptic reflexes in man has been studied by comparing H and T reflexes of the soleus and by blocking the effects of spindle activation by ischaemia of the leg. The Jendrassik manoeuvre equally enhances H and T reflexes provided that the test reflexes are small. The H reflex remains facilitated when the spindle activation cannot affect the soleus alpha-motoneurones--that is, when the Ia afferent nerve fibres from the soleus are blocked by ischaemia. It is concluded that the facilitating effect of the Jendrassik manoeuvre on the alpha-motoneurones is not predominantly routed via the gamma-loop.
Article
Full-text available
The effects of stretch repetition rate, prior warning stimuli and self administered stretch were examined on the size of the short and long latency components of the stretch reflex electromyographic EMG response in flexor pollicis longus and the flexor muscles of the wrist and fingers. Stretches of constant velocity and extent were given every 10 s, 5 s, 2 s, or 1 s to either the wrist or thumb during a small background contraction of the flexor muscles. The size of the long latency component of the stretch reflex (measured as the area under the averaged rectified EMG responses) declined dramatically at faster repetition rates, especially in the wrist and finger flexors. The size of the short latency component was relatively unaffected. The size of the electrically elicited H-reflex in forearm muscles also failed to habituate under the same conditions. If each individual trial of a series was examined, the long latency component of the stretch reflex EMG could be seen to decrease in size over the first three to six stretches if stretches were given every 1 s, but not if stretches were given every 10 s. When stretches were given every 5 s to either wrist or thumb, an electrical stimulus applied to the digital nerves of the opposite hand 1 s before stretch reduced the size of the long latency component of the reflex EMG response. The short latency component was unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
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To investigate the effect of voluntary teeth clenching on the isometric and isokinetic exercises of the lower limbs, the association of muscle strength (peak torque, PT) and muscle activities (integrated electromyographic activity per unit of time, iEMG/s) of the three muscles of the triceps surae with teeth clenching during isometric and isokinetic plantar flexion were simultaneously measured for 12 healthy male volunteers using a Cybex 6000 Extremity Testing and Rehabilitation System and a surface EMG analyzing system. The statistical analysis demonstrated that for the isometric exercise, PT and each iEMG/s significantly increased in association with teeth clenching, and a positive correlation existed between the biting force and each variable. In contrast, no association was found with teeth clenching for the isokinetic exercise. In this study, therefore, it was found that the effect of teeth clenching differed between the isometric and isokinetic exercises.
Chapter
The mechanisms involved in the active displacement of a body segment from an initial position toward a final one have been the focus of many investigations. Most attention in the recent past has been devoted to the analysis of the movement per se, the central control of the dynamic phase, and the final joint position. Movement, however, represents only the tip of an iceberg, the concealed part being the body posture that supports the performance of movement. The interaction of movement and posture, which has been investigated very little, is the focal point of this chapter.
Article
The branching pattern of individual pyramidal tract (PT) neurons of the monkey motor cortex was studied by activating these neurons antidromically from within the cervical motor nuclei and also from other regions of the spinal cord.1. Fifty-four neurons were activated from motor nuclei in the cervical cord. Twenty-eight of these were activated from one segment and six (11%) were activated from motor nuclei of different segments. The remaining 20 neurons were activated from motor nuclei and also from unspecified region(s) of the gray matter. 2. Another 156 neurons were activated from unspecified region(s) of cervical gray matter which could have been motor nuclei or outside the nuclei, and 64 of these were activated from more than one segment. 3. The branching patterns of PT neurons sending axons directly to motor nuclei innervating distal forelimb muscles suggested that they branch less than the rest of PT neurons.
Article
The discharge of muscle spindle afferents from monkey spindle afferents from monkey jaw-closing muscles was studied during mastication of natural foods by extracellular recording from the fibers or cell bodies of the tract and mesencephalic nucleus of the fifth nerve. In all, 39 muscle afferents were studied. The spindle associated with 18 of the afferents was positively identified by the afferent's response to gentle, localized palpation of either the temporalis or masseter muscle. Discharge patterns were observed during mastication, and in the majority of cases the qualitative passive response characteristics of the spindle afferent were determined. During steady chewing spindle afferent discharge typically paused briefly during the initial rapid upward part of the chewing cycle. Firing generally began as the jaw slowed its upward movement, and firing rates during the slow grinding portion of the upward movement were within the range of 50-80 spikes/s. All spindles exhibited a brisk discharge during the opening movement, typically within the range of 100-150 spikes/s. One-third of the spindle afferents exhibited a brief, high-frequency burst of firing at the very beginning of the opening movement, presumably as a result of stretch applied to a spindle just previously subjects to fusimotor excitation. Although the results of the study make it clear that spindles in jaw-closing muscles are coactived along with the extrafusal muscle fibers, the fusimotor bias does not seem capable of sustaining discharge in the face of rapid shortening of the muscle. Furthermore, the fact that discharge rate during opening, when the jaw-closing motoneurons are quiescent, is much higher than at any part of the closing cycle, when the motoneurons are active, suggests that the muscle spindles cannot provide the primary excitatory drive to the motoneurons.
Article
The effect on isometric strength of biting on three intraoral devices and habitual occlusion was analyzed. Only subjects who showed a relative weakness to the Isometric Deltoid Press (IDP) when biting as opposed to maintaining the mandible in an unsupported rest position were included in the study. Both in the original 35 subjects and the 23 subjects returning on the second day, performance wearing the appliance set by a functional criterion of peak strength (locking) to the IDP was significantly greater than wearing a placebo appliance and a bite raising appliance that deflected the mandible 1 mm to the left. Strength biting on the appliance set by a functional criterion was significantly greater than all these conditions. Strength biting in habitual trials that were matched with the deflection condition was found to be significantly greater than that biting in the placebo condition. It was concluded that a relationship does exist between bite and isometric strength. Previous speculation about the role of placebo effect was not substantiated by the data gathered in this experiment.
Article
A long lasting inhibition (greater than 8 s) of the soleus Hoffmann reflex (H-reflex) was evoked by a preceding soleus H-reflex, by a brief voluntary ankle flexor or extensor muscle contraction or by a tap applied to the Achilles tendon. The time course of this long lasting inhibition was similar in all these cases, suggesting that the same spinal mechanism is involved. Furthermore, it was shown that the post-activation depression may interfere with the determination of inhibitory or facilitatory effects on the H-reflex. It is stressed that when the onset of inhibitory or facilitatory effects on the soleus H-reflex is to be determined in relation to start of an ankle movement, either very long stimulus intervals (greater than 8 s) must be used, or the onset must be determined in relation to a reference value of the soleus H-reflex, which may be influenced by the long lasting inhibitory effect, but not yet by the succeeding muscle contraction.
Article
Facilitation of spinal reflex amplitude by remote muscle contraction, otherwise known as the Jendrassik maneuver (JM), was first shown over 100 years ago, yet the mechanism by which this facilitation operates remains undetermined. Earlier work has eliminated participation of the muscle spindle in JM-induced spinal reflex facilitation, leaving changes in postsynaptic (e.g., change in average soleus motoneuron membrane potential) and presynaptic (e.g., inhibition of presynaptic inhibition) mechanisms as viable candidates. We recorded background EMG in the soleus muscle during JM-induced soleus H-reflex facilitation in humans. The JM in this experiment consisted of wrist muscle contraction. Soleus background EMG was maintained by the subject at either a zero level (e.g., relaxed) or a specified moderate level prior to and during the JM. The JM increased H-reflex amplitude by comparable amounts in both situations, but had no effect on soleus background EMG. Given the well-known relationship between the average motoneuron pool membrane potential and background EMG, we conclude that JM facilitation of the soleus H-reflex is not caused by an increase in background excitatory input to the soleus motoneuron pool. Remaining candidates for mediation of JM induced H-reflex facilitation include change in stimulus-evoked afferent input at some point proximal to the muscle spindle, such as reduction in presynaptic inhibition, or a change in motoneuron input resistance.
Article
Muscle afferent activity from the triceps surae was recorded during experimentally induced alterations in amplitude of the Achilles tendon jerk. No changes in the neural afferent response to tendon percussion or in the background level of neural activity occurred when the reflex response was altered by discomfort, distraction, changes in attention, or changes in the rate of tendon percussion. Reinforcement of the Achilles tendon jerk by forceful contraction of the forearm muscles did not alter the relationship between intensity of the tendon tap and amplitude of the evoked neural afferent volley. Nevertheless, such maneuvers lowered the reflex threshold and raised reflex sensitivity so that a smaller afferent volley was required to produce a tendon jerk, and an increase in the afferent volley produced a disproportionately greater increase in reflex electromyographic activity than would have occurred at rest. Reinforcement maneuvers potentiated the H-reflex but did not alter the electrically induced afferent volley or the background level of neural activity. It is concluded that these changes in reflex responsiveness occurred through intrinsic spinal mechanisms independent of the fusimotor system.
Article
The study described in this article tested mandibular orthopedic repositioning appliances (MORA's) on eleven athletes to determine changes in muscle strength and efficiency (power) during various exertions. In the vertical jump and grip tests, a significant increase in muscle efficiency was recorded. An average increase of 5% in vertical jump was noted for the eleven subjects. All of the subjects showed an increase in the grip test, with a mean of 17.3%. However, there was no significant increase in strength recorded for the maximum hip sled or the bench press test.
Article
The present study was carried out to investigate whether there was any modulation of the spinal monosynaptic reflexes during mastication in the healthy humans and urethane-anesthetized rabbits and to elucidate the central neural mechanisms responsible for the modulation in the urethane-anesthetized rabbits. 1. Human soleus H-reflex was significantly facilitated during the rhythmical jaw movements and rhythmical gum chewing. 2. There was no significant difference in the magnitude of the facilitation between the jaw-opening and -closing phases. 3. In the rabbits, monosynaptic reflex (MSR) volleys recorded from the tibial nerve (TIB) innervating the crural extensors and the common peroneal nerve (CP) innervating the crural flexors tonically increased in amplitude during the masticatory movements induced by either intraoral stimulation or repetitive stimulation of the cortical masticatory area (CMA). 4. Antidromic field potentials in the anterior horn of the lumbar cord evoked by the stimulation of TIB and CP increased during the CMA-induced actual and fictive mastication. 5. There was no significant change in the amplitude of the directly evoked antidromic potential in the primary afferents by intraspinal stimulation during the CMA-induced mastication compared with the resting state. It was concluded that (1) the MSR of the crural muscles undergoes a tonic non-reciprocal facilitation during mastication, (2) the stomatognathic afferents induced during mastication are not essential for the facilitation, and (3) an increase in the excitability of motoneurons is mainly involved in the facilitation of the MSR during mastication.
Article
1. To determine the effects of motor activity in the jaw on more general motor behavior, we examined the modulation of the soleus H reflex in association with voluntary clenching of the teeth in healthy adult volunteers. 2. The amplitude of the H reflex increased remarkably during teeth clenching. The increase during maximal teeth clenching was greater than that induced either by maximal voluntary isometric contraction of the wrist extensors or by maximal voluntary clenching of the fists. 3. The increase in amplitude of the soleus H reflex showed a positive correlation with the strength of teeth clenching, as monitored by recording electromyographic (EMG) activity from the masseter muscle. 4. The increase in amplitude of the H reflex associated with teeth clenching started before the onset of the EMG activity of the masseter muscle, reached a peak shortly after the onset, and then declined to a plateau that continued in parallel with the masseter EMG until the end of teeth clenching. 5. The increase in amplitude of the H reflex in association with teeth clenching was partially decreased during the inhibitory masseteric reflex evoked by innocuous electrical stimulation of the lip. 6. It is concluded that the soleus H reflex is facilitated in association with voluntary teeth clenching, and that descending influences from the cerebral cortex, as well as peripheral afferent impulses from the oral-facial region, are involved in this facilitation. It is proposed that oral motor activity can exert strong influences on the motor activity of the other parts of the body.
Article
Since its initial description in 1883, the Jendrássik maneuver (JM) has been used in clinical neurological practice as an effective means of potentiating the tendon tap in neurologically impaired patients. The JM also potentiates its electrical analogue, the Hoffman (H-) reflex, but the mechanism of the reflex modulation has not been clearly established. We studied soleus H-reflex modulation in neurologically intact subjects while at rest and during a mild plantarflexion contraction (EMG level equivalent to approximately 10% maximum voluntary contraction). The control H-reflex was elicited by stimulating the tibial nerve in the popliteal fossa with single pulses of 1 ms duration. Conditioning of the reflex was by: (1) increasing segmental presynaptic inhibition via common peroneal nerve (CP) stimulation; (2) pulling the arms and clenching the teeth (JM); or (3) applying both together (JM+CP). CP stimulation significantly (P<0.05) suppressed the H-reflex (50% Hmax), while JM significantly (P<0.05) facilitated it during contraction. From either an analysis of the grouped data or by a within-subject analysis, we found that the combined effect of stimulating JM+CP was significantly lower than JM alone, but did not differ from control values or from CP alone. The simplest mechanism would be that the effects of the two sum algebraically on the interneurones producing segmental presynaptic inhibition of the H-reflex.
Article
A previous study has demonstrated that the soleus H reflex is facilitated in association with voluntary teeth clenching in proportion with biting force in humans. The present study tried to elucidate the functional significance of this facilitation of the soleus H reflex, by examining 1) whether the facilitation of the H reflex is reciprocal or nonreciprocal between the ankle extensors and flexors and 2) whether the reciprocal Ia inhibition of crural muscles is facilitated or depressed in association with voluntary teeth clenching. The H reflex of the pretibial muscles was evoked by stimulation of the common peroneal nerve in seven healthy subjects with no oral dysfunction. The pretibial H reflex was facilitated in association with voluntary teeth clenching in a force-dependent manner. The facilitation started preceding the onset of electromyographic activity of the masseter muscle. Stimulation of the common peroneal nerve at low intensities subthreshold for evoking the M wave of the pretibial muscles inhibited the soleus H reflex after a short latency corresponding with a disynaptic inhibition, indicating that the reciprocal Ia inhibition was depressed in association with voluntary teeth clenching. Thus, the present study has shown that voluntary teeth clenching evokes a nonreciprocal facilitation of ankle extensor and flexor muscles and attenuated reciprocal Ia inhibition from the pretibial muscles to the soleus muscle. It is concluded that voluntary teeth clenching contributes to improve stability of stance rather than smoothness of movements.
Remote facilitation of H-reflex during voluntary contraction of orofacial and limb muscles Tutorials in mo-tor behavior II
  • A Hayashi
  • Ra Konopacki
  • Hunker
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Hayashi A, Konopacki RA, Hunker CJ. Remote facilitation of H-reflex during voluntary contraction of orofacial and limb muscles. In: Stelmach GE, Requin J, editors. Tutorials in mo-tor behavior II. Amsterdam: Elsevier; 1992. p 475–482.
Modulation of spinal monosynaptic reflexes during rhythmi-cal jaw movements
  • N Hagiya
  • T Miyahara
  • T Tanaka
  • T Ohyama
  • Nakamura
Hagiya N, Miyahara T, Tanaka T, Ohyama T, Nakamura Y. Modulation of spinal monosynaptic reflexes during rhythmi-cal jaw movements. Jpn J Physiol 1994;44(suppl 1):S217.
Modulation of tibialis anterior H reflex during mastication in man
  • T Takahashi
  • Y Takada
  • T Miyahara
  • T Ohyama
  • Nakamura
Takahashi T, Takada Y, Miyahara T, Ohyama T, Nakamura Y. Modulation of tibialis anterior H reflex during mastication in man. Jpn J Physiol 1999;49(suppl):S166.
Modulation of soleus H‐reflex during rhythmical jaw movements in humans
  • Hagiya N
Hagiya N, Miyahara T, Ohyama T, Nakamura Y. Modulation of soleus H-reflex during rhythmical jaw movements in hu-mans. J Dent Res 1992;71:1045.
Modulation of tibialis anterior H reflex during mastication in man
  • Takahashi T