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Effect of masticating chewing gum on postural stability during upright standing
Abstract
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.
... Over the years, a lot of research was conducted to investigate the relationship between the postural control and the craniomandibular systems as well as the clinical impacts (e.g., Cuccia & Caradonna, 2009;Nowak et al., 2023;Sakaguchi et al., 2007;Solovykh et al., 2012). Various changes in the position or in the activities of the craniomandibular system were shown to affect the body posture and its control (e.g., Alghadir et al., 2015aAlghadir et al., , 2015bAlghadir et al., , 2015cGangloff et al., 2000;Hegab, 2015;Khan et al., 2013;Kushiro & Goto, 2011;Munhoz & Marques, 2009;Sakaguchi et al., 2007;Treffel et al., 2016). However, it should also be noted that not all previous studies support the relationship between the postural control and craniomandibular systems (e.g., Ferrario et al., 1996;Alghadir et al., 2022). ...
... Change in the activities of the craniomandibular system was shown to influence the postural control system, such as chewing (Alghadir et al., 2015b;Kushiro & Goto, 2011) or jaw clenching (Alghadir et al., 2015c;Hellmann et al., 2011a;Nakamura et al., 2017;Ringhof, Leibold, et al., 2015;Tanaka et al., 2006;Tomita et al., 2021;Treffel et al., 2016). ...
... Chewing cycles are semiautomatic motor behavior and involve well-trained muscles (Hellmann et al., 2011a;Lund, 1991). Kushiro and Goto (2011) analyzed the effects of chewing gum on the static steady-state balance and found that CoP stability increased during the mastication of chewing gum. On the other hand, in another study analyzing the changes in body oscillations during unilateral chewing of a rubber cube and maximum jaw clenching, no effects of these jaw motor tasks on body sway could be detected (Hellmann et al., 2011a). ...
... Kushiro and Goto examined the effects of masticatory chewing on the postural stability of healthy adults standing upright. The results suggest that mastication of chewing gum could enhance postural stability during upright standing, possibly by improving mental health (Kushiro & Goto, 2011). ...
... Several studies showed that chewing improves muscle activity, force production, and rate of force development (Ginszt et al., 2020;Iwasaki et al., 1994). Chewing gum affects postural control by enhancing postural stability (Kushiro & Goto, 2011). In addition to physical improvement, chewing can help individuals cope with psychological stress, leading to mental health improvements (Azuma et al., 2017). ...
Chewing is a simple and effective method for managing psychological stress and maintaining optimal physical and mental health. This study aimed to systematically review the potential benefits and disadvantages of chewing in sports. We conducted a comprehensive literature search for all relevant articles sourced from the Cochrane Central Register of Controlled Trials, MEDLINE, and PUBMED. We used “chewing OR mastication OR masticatory” and “sport OR sports OR training OR exercise OR physical fitness OR athletic OR athlete OR performance.” We adopted a three-step screening process for titles, abstracts, and full-texts to select eligible articles. After applying our inclusion and exclusion criteria, we performed a full-text screening of 101 articles. The results showed that chewing could improve muscle activation, force production, muscle strength, and postural stability, positively affecting sports performance, especially in rugby, judo, kendo, and climbing. The beneficial effects of chewing on sports performance may be associated with the activation of central nervous system circuits, an increase in arousal level and alertness, and improvements in cognitive ability. In contrast, chewing gum poses a potential risk of laryngeal spasm during activities, such as swimming or cricket. Attention should be paid to chewing gum while engaging in sports.
... 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]. ...
... Moreover, it also needs further analysis on the subjects with the other patterns of masticatory movement path other than Pattern I (the pattern of masticatory movement path with a linear or concave opening path and a convex closing path) [30]. Kushiro et al. [13] investigated the effect of masticating chewing gum on the postural stability during upright standing, using only the force plate for postural assessment, and they suggested that mastication of chewing gum affects the postural control by enhancing the postural stability during upright standing. Goto et al. [14] also conducted a similar study and reported that the chewing gum indirectly affected postural control by influencing the vestibular function to stabilize posture during upright standing. ...
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.
... Many studies have reported on the positive effects of chewing gum on cognition, including alertness, attention, cognitive processing speed, and memory (Wilkinson et al. 2002;Tucha et al. 2004;Miles and Johnson 2007;Ono et al. 2007;Scherder et al. 2008;Kushiro and Goto 2011;Tucha and Simpson 2011;Hirano et al. 2013). By contrast, only a few studies have reported on the effect on motor function (Ono et al. 2007;Kushiro and Goto 2011) and no study on the cortical effect of chewing gum on a motor task has been reported. ...
... Many studies have reported on the positive effects of chewing gum on cognition, including alertness, attention, cognitive processing speed, and memory (Wilkinson et al. 2002;Tucha et al. 2004;Miles and Johnson 2007;Ono et al. 2007;Scherder et al. 2008;Kushiro and Goto 2011;Tucha and Simpson 2011;Hirano et al. 2013). By contrast, only a few studies have reported on the effect on motor function (Ono et al. 2007;Kushiro and Goto 2011) and no study on the cortical effect of chewing gum on a motor task has been reported. In this study, we hypothesized that chewing gum could affect the motor function. ...
Nine right-handed normal subjects were recruited for this study. We compared the cortical activation during execution of hand movements (right finger flexion-extension) with that during execution of hand movements while chewing gum (right side chewing). We found that execution of hand movements while chewing gum induced less activation in the contralateral SM1 than hand movements alone. Based on our findings, it appears chewing gum during execution of hand movements enhanced the efficiency of hand movements.
... Our findings corroborate a recent study with 12 healthy adults, showing that the postural stability during quiet standing tends to enhance during chewing of gum (Kushiro and Goto 2011). However, in contrast to the test conditions of our study, the subjects were standing with open eyes and on a firm surface. ...
... High stress has been recorded during anxiety. Chewing is known to lower this stress level (Stephens and Tunney 2004), improve mental condition including concentration (Kushiro and Goto 2011), enhance cognitive performance by reducing the reaction time in several cognitive tasks, and alleviate mood (Smith 2010;Wilkinson et al. 2002;Tahara et al. 2007). Hence, chewing of gum may indirectly influence and improve postural stability. ...
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.
... Posturography is useful for investigating global balance performance (Kushiro & Goto, 2011). We found that anxiety affects postural perturbation in the anteroposterior axis, possibly indicating that anxiety affects the interactions between visual inputs and vestibular as well as somatosensory inputs in the maintenance of postural balance in patients complaining of dizziness (Goto et al. 2011a). ...
... In addition, the effect of visual input was investigated. Posturography is a useful tool for investigating the effects of various conditions (Kushiro & Goto, 2011), and we used it to evaluate postural sway. Anxiety levels were assessed by the hospital anxiety and depression scale (HADS). ...
... This technique has been widely used in a variety of scientific fields [1]. Recently, we have shown that in healthy subjects, static balance improves while chewing gum [2]. However, the effect of chewing gum on patients with balance disorders is not yet known. ...
... This result supports the conclusions of our previous report that mastication does not directly affect postural stability in healthy subjects. Rather, chewing gum improves the mental condition including concentration, which subsequently influences postural stability [2]. Chewing gum mainly acts on psychological factors, such as the release of anxiety, and does not directly affect postural control. ...
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.
... 6 Since balance control is task-specific rather than a general ability, it is useful to study balance tasks other than static stance. 7 Studies showed the stabilising effects of oral motor tasks when standing on firm and foam surfaces [8][9][10][11][12][13][14][15] and during dynamic balancing tasks on unstable platforms. 16 Fadillioglu et al. compared the effect of jaw clenching, tongue pressing against the palate and habitual lower jaw position on postural performance during a dynamic reactive balance task on an oscillating platform. ...
Background: Jaw clenching improves dynamic reactive balance on an oscillating platform during forward acceleration and is associated with decreased mean sway speed of different body regions.
Objective: It is suggested that jaw clenching as a concurrent muscle activity facilitates human motor excitability, increasing the neural drive to distal muscles. The underlying mechanism behind this phenomenon was studied based on leg and trunk muscle activity (iEMG) and co-contraction ratio (CCR).
Methods: Forty-eight physically active and healthy adults were assigned to three
groups, performing three oral motor tasks (jaw clenching, tongue pressing against the palate or habitual lower jaw position) during a dynamic one-legged
stance reactive balance task on an oscillating platform. The iEMG and CCR of posture-relevant muscles and muscle pairs were analysed during platform forward acceleration.
Results: Tongue pressing caused an adjustment of co-contraction patterns of distal
muscle groups based on changes in biomechanical coupling between the head and
trunk during static balancing at the beginning of the experiment. Neither iEMG nor
CCR measurement helped detect a general neuromuscular effect of jaw clenching on the dynamic reactive balance.
Conclusion: The findings might indicate the existence of robust fixed patterns of rapid postural responses during the important initial phases of balance recovery.
... 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]. ...
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.
... Researchers have also investigated the relationship between mastication and body posture [11][12][13], and suggest the possibility that mastication affects the postural control by enhancing the postural stability. All these reports examined the relationship between mastication and standing posture. ...
... This is consistent with previous studies showing that mastication can lead to an increase in the neural drive and excitability of the alpha motor neuron pool for muscles of both the upper and lower limbs [5,11,12]. However, previous masticationrelated studies have been conducted simply in standing or standing balance or walking situations and showed only one lower limb muscle such as the tibialis anterior (TA) [5,11,17]. In this study, even in a more dynamic task, the same neural mechanisms for the increased excitation of the various lower extremities used for the task were demonstrated during gum chewing. ...
PURPOSE: Gum chewing stimulates the sympathetic nervous system and increases energy consumption. However, the effect of mastication on physical activity remains unclear. This study aimed to investigate the effect of gum masticatory movement on physiological markers related to walking and muscle activation during cycling in different patient groups.METHODS: Using a randomized crossover design, 25 participants participated in walking trials with a 1-week washout; the trials included chewing gum (GUM), taking a candy with the same ingredients as the gum (CAN), and no ingestion (CON). Energy expenditure (EE), metabolic equivalent (MET), oxygen consumption (VO2), and heart rate were measured using a portable metabolic device. The walking distance was also calculated. In the cycling experiment, the other 19 participants randomly completed 7 minutes of the three trials (GUM, CAN, CON) with a 15-minute break. The mean cycling period (MCP), cycle number (CN), coefficient of variation of the cycling period (CV), and integrated electromyography (iEMG) results were measured using the Delsys Trigno™ Wireless EMG System.RESULTS: The walking distance was significantly higher in the GUM group than in the CAN and CON groups by an average of 78 m (7.4%, p<.05). Comparing the GUM and CON groups, EE, METs, and VO2 demonstrated a partially significant increase after 15 minutes. In the cycling experiment, there were no significant differences in the effects of the trials on cycling performance (MCP, CN, CV). However, significant differences were observed in the GUM group for the iEMG results.CONCLUSIONS: Our study results suggest that gum chewing improves physical performance, such as walking distance, and improves energy metabolism, such as EE and METs. Additionally, it can influence the improvement in the lower limb muscle activity during cycling.
... Influence of jaw sensory-motor system on vestibular, neck, and ocular systems has been shown (Alghadir, Zafar, Iqbal, & Al-Eisa, 2018;Davies, 1979;Ehrlich, Garlick, & Ninio, 1999;Hellmann, Giannakopoulos, Blaser, Eberhard, & Schindler, 2011;Park et al., 2014), and thus, it has the capacity to affect posture control. Variation in activation pattern of the jaw sensory-motor system while maximum biting, sub-maximum biting, clenching or chewing has been shown to modulate strategies of central postural motor control mechanisms differently (Alghadir et al., 2014;Hellmann et al., 2011;Kushiro & Goto, 2011). These include improvement in sports performance, distal muscle strength, and postural balance (Cherry, Brown, Coburn, & Noffal, 2010;Hosoda et al., 2007). ...
Background:
Jaw sensory-motor system has been shown to affect static balance of the body. It would be interesting to know whether it can influence dynamic balance as well. The objective of this study is to examine the influence of different jaw positions on dynamic balance using the Y-balance test.
Methods:
Eighty healthy male participants aged 20-35 years were invited to participate in this study. Dynamic balance was measured by the Y-balance test in three directions (anterior, posteromedial, and posterolateral) for each leg separately in three jaw positions: resting jaw (control), open-jaw, and clenched jaw.
Results:
There were no significant differences in reach distances between the different jaw positions except in the posterolateral direction. In comparison with resting jaw position, reach distance was significantly higher in open-jaw position for the right leg and in clenched and open-jaw positions for the left leg in the posterolateral direction.
Conclusions:
Although various studies have shown direct or indirect influence of jaw sensory-motor system on static postural control, results of this study point to limited relation with dynamic postural control among healthy subjects. However, it supports the potential of the jaw sensory-motor system to affect motor control during functional tasks in patients with postural instability or similar disorders.
... There is a debate as to whether trigeminal sensorimotor signals may affect posture and movement. In particular, postural control seems to be influenced by the occlusal condition (Ohlendorf et al., 2014;Julià-Sánchez et al., 2015;see, however, Perinetti, 2006), temporomandibular joint (TMJ) disorders (Chaves et al., 2014) and orofacial motor activity (Kushiro and Goto, 2011;Ringhof et al., 2015). These data are consistent with the observation that sensorimotor signals elicited during isometric clenching are very effective in increasing the excitability of spinal motoneurons (Miyahara et al., 1996). ...
In order to assess possible influences of occlusion on motor performance, we studied by functional magnetic resonance imaging (fMRI) the changes in the blood oxygenation level dependent (BOLD) signal induced at brain level by a finger to thumb motor task in a population of subjects characterized by an asymmetric activation of jaw muscles during clenching (malocclusion). In these subjects, appropriate occlusal correction by an oral orthotic (bite) reduced the masticatory asymmetry. The finger to thumb task was performed while the subject’s dental arches were touching, in two conditions: (a) with the teeth in direct contact (Bite OFF) and (b) with the bite interposed between the arches (Bite ON). Both conditions required only a very slight activation of masticatory muscles. Maps of the BOLD signal recorded during the movement were contrasted with the resting condition (activation maps). Between conditions comparison of the activation maps (Bite OFF/Bite ON) showed that, in Bite OFF, the BOLD signal was significantly higher in the trigeminal sensorimotor region, the premotor cortex, the cerebellum, the inferior temporal and occipital cortex, the calcarine cortex, the precuneus on both sides, as well as in the right posterior cingulate cortex. These data are consistent with the hypothesis that malocclusion makes movement performance more difficult, leading to a stronger activation of (a) sensorimotor areas not dealing with the control of the involved body part, (b) regions planning the motor sequence, and (c) the cerebellum, which is essential in motor coordination. Moreover, the findings of a higher activation of temporo-occipital cortex and precuneus/cingulus, respectively, suggest that, during malocclusion, the movement occurs with an increased visual imagery activity, and requires a stronger attentive effort.
... Evidences shown in the studies of Funakoshi et al. (4) and Deriu et al. (5) proved that the activation of masticatory muscles was different at different head positions. On the other hand, Kushiro et al. (6) showed a reverse effect that chewing gums increased postural stability when people stood uprightly. Besides, animal experiments suggested that there could be an anatomical connection between the vestibular nuclei and trigeminal motoneurons in the brainstem (7)(8)(9). ...
The performance of the masticatory muscle is frequently affected and presents high heterogeneity poststroke. Surface electromyography (EMG) is widely used to quantify muscle movement patterns. However, only a few studies applied EMG analysis on the research of masticatory muscle activities poststroke, and most of which used single parameter—root mean squares (RMS). The aim of this study was to fully investigate the performance of masticatory muscle at different head positions in healthy subjects and brainstem stroke patients with multiparameter EMG analysis. In this study, 15 healthy subjects and six brainstem stroke patients were recruited to conduct maximum voluntary clenching at five different head positions: upright position, left rotation, right rotation, dorsal flexion, and ventral flexion. The EMG signals of bilateral temporalis anterior and masseter muscles were recorded, and parameters including RMS, median frequency, and fuzzy approximate entropy of the EMG signals were calculated. Two-way analysis of variance (ANOVA) with repeated measures and Bonferroni post hoc test were used to evaluate the effects of muscle and head position on EMG parameters in the healthy group, and the non-parametric Wilcoxon signed rank test was conducted in the patient group. The Welch–Satterthwaite t-test was used to compare the between-subject difference. We found a significant effect of subject and muscles but no significant effect of head positions, and the masticatory muscles of patients after brainstem stroke performed significantly different from healthy subjects. Multiparameter EMG analysis might be an informative tool to investigate the neural activity related movement patterns of the deficient masticatory muscles poststroke.
... In other words, chewing gum protects teeth against plaque and cavity formation. Research has also shown that chewing gum positively affects postural stability (Kushiro and Goto, 2011). Finally, chewing gum reduces stress, fatigue, anxiety and depression and might have a possible effect on stress coping (Konno et al., 2016). ...
... Particularly in the field of clinical otolaryngology, COP measurement is a widely-used diagnostic method for vestibular patients 13,14) . To elucidate the effect of cognition on postural stability, the author performed experiments with normal adults 15) . Subjects standing up-canal system as well as in the otolith system, particularly the utricular system 7) . ...
Humans sequentially perceive spatial information surrounding them when performing intended motor movements. Precise spatial information is constructed in the brain by integrating sensory information such as visual, vestibular, and somatosensory inputs. Visual input is considered an essential source of stable spatial perception in our daily lives. In addition, and in parallel with visual function, vestibular and somatosensory systems have important roles in spatial perception, particularly when unconscious. Although the vestibular system is not considered one of the “five senses” of human sensation, this system serves a couple of important functions. One important function is the prompt stabilization of the head and body against outer disturbances. In addition, vestibular signals are utilized in the higher order of the brain for construction of three-dimensional spatial perception. In this review, the functional properties, as well as the neural system, of the vestibular system are introduced in relation to spatial perception.
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.
Several studies have confirmed the neuromuscular effects of jaw motor activity on the postural stability of humans, but the mechanisms of functional coupling of the craniomandibular system (CMS) with human posture are not yet fully understood. The purpose of our study was, therefore, to investigate whether submaximum biting affects the kinematics of the ankle, knee, and hip joints and the electromyographic (EMG) activity of the leg muscles during bipedal narrow stance and single-leg stance. Twelve healthy young subjects performed force-controlled biting (FB) and non-biting (NB) during bipedal narrow stance and single-leg stance. To investigate the effects of FB on the angles of the hip, knee, and ankle joints, a 3D motion-capture system (Vicon MX) was used. EMG activity was recorded to enable analysis of the coefficient of variation of the muscle co-contraction ratios (CVR) of six pairs of postural muscles. Between FB and NB, no significant differences were found for the mean values of the angles of the ankle, knee, and hip joints, but the standard deviations were significantly reduced during FB. The values of the ranges of motion and the mean angular velocities for the three joints studied revealed significant reduction during FB also. CVR was also significantly reduced during FB for five of the six muscle pairs studied. Although submaximum biting does not change the basic strategy of posture control, it affects neuromuscular co-contraction patterns, resulting in increased kinematic precision.
Copyright © 2015 Elsevier B.V. All rights reserved.
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.
Recent research suggests that chewing gum may improve aspects of cognitive function and mood. There is also evidence suggesting that chewing gum reduces stress. It is important, therefore, to examine these two areas and to determine whether contextual factors (chewing habit, type of gum, and personality) modify such effects.
The aims of the present study were: (i) to determine whether chewing gum improved mood and mental performance; (ii) to determine whether chewing gum had benefits in stressed individuals; and (iii) to determine whether chewing habit, type of gum and level of anxiety modified the effects of gum.
A cross-over study involving 133 volunteers was carried out. Each volunteer carried out a test session when they were chewing gum and without gum, with order of gum conditions counterbalanced across subjects. Baseline sessions were conducted prior to each test session. Approximately half of the volunteers were tested in 75 dBA noise (the stress condition) and the rest in quiet. Volunteers were stratified on chewing habit and anxiety level. Approximately, half of the volunteers were given mint gum and half fruit gum. The volunteers rated their mood at the start and end of each session and had their heart rate monitored over the session. Saliva samples were taken to allow cortisol levels (good indicator of alertness and stress) to be assayed. During the session, volunteers carried out tasks measuring a range of cognitive functions (aspects of memory, selective and sustained attention, psychomotor speed and accuracy).
Chewing gum was associated with greater alertness and a more positive mood. Reaction times were quicker in the gum condition, and this effect became bigger as the task became more difficult. Chewing gum also improved selective and sustained attention. Heart rate and cortisol levels were higher when chewing which confirms the alerting effect of chewing gum.
Overall, the results suggest that chewing gum produces a number of benefits that are generally observed and not context-dependent. In contrast to some previous research, chewing gum failed to improve memory. Further research is now required to increase our knowledge of the behavioral effects of chewing gum and to identify the underlying mechanisms.
The purpose of this study was to investigate how attentional focus on body sway affects postural control during quiet standing. To address this issue, sixteen young healthy adults were asked to stand upright as immobile as possible on a force platform in both Control and Attention conditions. In the latter condition, participants were instructed to deliberately focus their attention on their body sways and to increase their active intervention into postural control. The critical analysis was focused on elementary motions computed from the centre of pressure (CoP) trajectories: (1) the vertical projection of the centre of gravity (CoG(v)) and (2) the difference between CoP and CoG(v) (CoP-CoG(v)). The former is recognised as an index of performance in this postural task, whilst the latter constitutes a fair expression of the ankle joint stiffness and is linked to the level of neuromuscular activity of the lower limb muscles required for controlling posture. A frequency-domain analysis showed increased amplitudes and frequencies of CoP-CoG(v) motions in the Attention relative to the Control condition, whereas non-significant changes were observed for the CoG(v) motions. Altogether, the present findings suggest that attentional focus on body sway, induced by the instructions, promoted the use of less automatic control process and hampered the efficiency for controlling posture during quiet standing.
This study tests the hypothesis that chewing gum leads to cognitive benefits through improved delivery of glucose to the brain, by comparing the cognitive performance effects of gum and glucose administered separately and together. Participants completed a battery of cognitive tests in a fully related 2×2 design, where one factor was Chewing Gum (gum vs. mint sweet) and the other factor was Glucose Co-administration (consuming a 25 g glucose drink vs. consuming water). For four tests [Auditory Verbal Learning Task (AVLT) Recall, Digit Span, Spatial Span and Grammatical Transformation), beneficial effects of chewing and glucose were found, supporting the study hypothesis. However, on AVLT Delayed Recall, enhancement due to chewing gum was not paralleled by glucose enhancement, suggesting an alternative mechanism. The glucose delivery model is supported with respect to the cognitive domains: working memory, immediate episodic long-term memory and language-based attention and processing speed. However, some other mechanism is more likely to underlie the facilitatory effect of chewing gum on delayed episodic long-term memory.
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
Purpose: The purpose of this study was to investigate the effects of chewing and clenching on salivary cortisol levels as an indicator of stress.
Materials and Methods: Seventeen healthy dentulous subjects were given arithmetic exercises to perform within a 20-minute time limit in order to elicit stress (stress loading). In the first experiment (chewing), after stress loading, the subjects were asked to chew a paraffin wax while reading printed material (books, magazines, etc.) in silence for 10 minutes. The same procedure was then carried out again for control purposes, but this time the subjects were not required to chew wax. In the second experiment (light clenching), after stress loading, the subjects were required to carry out 5 seconds of light clenching followed by 5 seconds of rest repeatedly over a 3-minute period. The whole 3-minute process was repeated a total of three times. The control data for this second experiment consisted of measurements taken during the rest periods. Saliva specimens were collected in both experiments both before stress loading and after each procedure during 1-minute intervals to measure cortisol levels.
Results: In the chewing experiment, salivary cortisol levels were significantly reduced by chewing, compared with those in the controls (p < 0.05). This reduction in salivary cortisol was observed during chewing over a 10-minute period following stress loading. In the clenching experiment, salivary cortisol levels also showed a significant reduction during clenching, compared with those in the controls (p < 0.05).
Conclusions: These results suggest that chewing and clenching promote relaxation in subjects under stress.
We have previously reported that state anxiety scores were positively correlated with postural sway while standing upright and gazing at a visual target (Ohno et al., 2004 [16]). The present study examines the effect of anticipatory anxiety and visual input on postural control in healthy individuals. An unpredictable aversive sound (100dB SPL) was delivered in order to induce anticipatory anxiety. Participants were asked to stand upright on a force plate with their eyes open and closed, and their center of pressure (COP) was measured. Analysis of the postural parameters revealed that the path lengths of the COP and the enveloped areas were greater in the anticipatory situation with the aversive sound than in the silent situation. Fast Fourier transform analysis showed that the frequency component related to vestibular inputs (0.1-1.0Hz) was increased during the anticipatory situation. The lower frequency (<0.1Hz) component was decreased in the medio-lateral axis during anticipation with the eyes closed due to shifting mean power frequencies to high frequency. The results suggest that anticipatory anxiety in healthy participants amplified the sway regardless of whether the eyes were open or closed, and that the vestibular inputs greatly influenced the amplification of postural sway.
The notion that chewing gum may relieve stress was investigated in a controlled setting. A multi-tasking framework which reliably evokes stress and also includes performance measures was used to induce acute stress in the laboratory. Using a randomised crossover design forty participants (mean age 21.98 years) performed on the multi-tasking framework at two intensities (on separate days) both while chewing and not chewing. Order of workload intensity and chewing conditions were counterbalanced. Before and after undergoing the platform participants completed the state portion of the State-Trait Anxiety Inventory, Bond-Lader visual analogue mood scales, a single Stress Visual Analogue Scale and provided saliva samples for cortisol measurement. Baseline measures showed that both levels of the multi-tasking framework were effective in significantly reducing self-rated alertness, calmness and contentment while increasing self-rated stress and state anxiety. Cortisol levels fell during both levels of the stressor during the morning, reflecting the predominance of a.m. diurnal changes, but this effect was reversed in the afternoon which may reflect a measurable stress response. Pre-post stressor changes (Delta) for each measure at baseline were subtracted from Delta scores under chewing and no chewing conditions. During both levels of stress the chewing gum condition was associated with significantly better alertness and reduced state anxiety, stress and salivary cortisol. Overall performance on the framework was also significantly better in the chewing condition. The mechanisms underlying these effects are unknown but may involve improved cerebral blood flow and/or effects secondary to performance improvement during gum chewing.
Head extension may cause a physiological vertigo and postural imbalance separate and distinct from basilar insufficiency. This physiological imbalance mainly is due to a vestibular sensory deficiency when the utricular otoliths are beyond their working range because of the change in head position. Since the intact visual and somatosensory control hope widely compensate for the vestibular deficiency, head-extension vertigo is of particular concern only in certain stimulus situations or diseases in which the stabilizing input from the eyes or joint receptors is reduced. Balance training on foam rubber with head extension and closed eyes improved postural-sway activity up to 50% within five days. A daily short-term training effect and a long-term training effect together form a typical exponential sawtooth curve of postural stability over time. After termination of training, learned balance skill exponentially returns to the pretraining values within weeks. The percentage of improvement through training depends on the amount of initial instability. Clinicians should treat ataxia by exposing patients to stimulus situations producing increasing body instability in order to activate sensorimotor rearrangement.
Mostly techniques measuring the vestibulo-ocular reflex (VOR) have been used for the evaluation of patients with dizziness problems. Some investigators, however, have also tried to take into account the vestibulospinal reflex (VSR). So recording techniques for the Romberg-test have been proposed and called posturography (PG). By interfering with the visual and proprioceptive sensory inputs during this PG-testing one tries to find out how ‘sensory interaction’ is organized in the balance performance of the patient examined. To interfere with vision, closure of the eyes has been commonly used and to interfere with proprioception, the patient can be put on foam-rubber, which makes the contribution of the foot-ankle proprioception less adequate. These interferences are applied once separately and once combined. The degree of ‘abnormality’ is assessed by a score-system for parameters surface (S) and velocity (V), which measure the postural sway. A comparison of tests with and without influence on the sensory inputs gives an idea of the sensory interaction. Patients with peripheral vestibular disorders were examined: patients with BPPV, with spontaneous vertigo attacks and with a sudden vestibular deficit.
When applying this evaluation technique different formulae or patterns can be found. Firstly complete normal evaluation, which means that there is no influence of the vestibular disturbance upon the PG results. Secondly a normal balance when using all available sensory information, but disturbed balance as soon as one of the sensory inputs is influenced by the test conditions. Thirdly striking destabilization when closing the eyes. Fourthly striking destabilization when misleading the ankle and foot proprioceptor. Fifthly a combined effect, when the vestibular input is the only one not influenced by the test conditions and sixthly no specific effect, no complementary compensatory effect of this sensory interaction.
In the group of patients with peripheral vestibular disorders, no special pattern linked to a peripheral syndrome could be found. Not only in the acute stage could abnormal PG be found: in fact, PG provides ‘functional’ data, which are complementary to the ‘classical’ evaluation and subdivide the patients into other sub-categories. The sensory interaction testing points to some conditions where balance will be more inclined to be troubled.
Healthy young adults (n = 39) were asked to perform four different secondary cognitive tasks during quiet unperturbed stance, in order to investigate the influence of physiological arousal and attention distraction on the control of spontaneous postural sway. During each task, postural activity was quantified in terms of center-of-pressure displacement, leg-muscle activation, and ankle and hip rotation. Arousal was monitored via skin conductance, and questionnaires were used to assess state anxiety. Respiratory trunk movements were also recorded, to assess potential arousal-related destabilizing effects, but failed to show a strong association with the postural measures. The nature of the secondary task affected the postural responses in that subjects tended to lean slightly forward, and exhibited higher levels of activation in tibialis anterior, when performing a mental-arithmetic task. Although this task affected both attention and arousal, the leaning effect was limited to subjects who reported higher levels of anxiety-related autonomic or somatic symptoms during testing, and the degree of leaning was correlated with the level of physiological arousal. A secondary task that diverted attention but did not affect physiological arousal (listening to a spoken-word recording) failed to elicit changes in postural response. These findings suggest that the changes in leaning were associated with task-related changes in physiological arousal, and highlight the need to account for the potentially confounding influence of arousal when studying attentional effects. Given the potential influence on stability, the results also suggest that leaning should be monitored or controlled during balance assessment, particularly when dealing with individuals who may be anxious or afraid of falling.
To examine whether the postural balance is influenced by the degree of anxiety, body sway during orthostatic standing while gazing at a visual target was examined in college students. Students, physically and mentally healthy, were divided into two groups according to the degree of state anxiety; high anxiety group (HA) and low anxiety group (LA). A fast Fourier transform analysis of the postural sway in antero-posterior axis showed that frequency components of 0.02-0.21 Hz, reflecting vestibular inputs, were 16% greater and those of 2.02-10.0 Hz, reflecting somatosensory inputs, were 24% smaller in HA. These differences between HA and LA were abolished when the eyes were closed. It is concluded that the interactions of visual inputs with vestibular and somatosensory inputs are influenced by anxiety.
Previous studies have shown that anxiety and balance disorders could be related; however, the association between psychological processes and equilibrium remains ambiguous. In this study, we have examined whether mood states and anxiety may influence the ability to use the somatosensory, visual and vestibular systems and affect balance control in healthy subjects. Seven male students were submitted to a program testing equilibrium over a 12-day period, during which moods and anxiety states were assessed using self-evaluated questionnaires. Significant negative correlations were found between moods, including anxiety, and the subject's sensory and motor systems of balance control, suggesting that low moods may alter balance performance. However, depending on the type of mood, it is likely that adverse changes in mood states may affect balance in different ways, either through the sensory organization or motor control.
The purpose of this study is to investigate human brain activity during mastication using fMRI. Twelve right-handed normal subjects performed two tasks: chewing of gum at their own pace, and imitating the movements of chewing gum. In order to reveal which areas of the brain are more strongly activated while chewing gum, we performed the conjunction analyses of gum chewing minus sham chewing with gum chewing minus rest. The common activity in the orofacial sensorimotor and premotor cortex was subtracted out since it was common to both tasks, but there were some differences in activity in some prefrontal and posterior parietal cortex areas. Our results suggest that a fronto-parietal network for mastication exists and may contribute to higher cognitive information processing.
To examine the possibility that anxiety affects the control of postural balance, state anxiety, and body sway during orthostatic standing were measured twice in college students with an interval of 1 month. Correlations between the changes in state anxiety and the parameters of body sway were examined by Pearson's correlation analysis. The changes in the enveloped area of body sway and in the maximum length of the antero-posterior body sway showed a positive correlation with the changes in state anxiety (r = 0.543 and 0.659, respectively). The data showed that an increase in anxiety caused instability in the control of postural balance. These correlations were abolished when the eyes were closed. In conclusion, anxiety affects the processing of visual input and influences the net performance of postural control.
Two experiments examined whether chewing spearmint gum can affect the initial learning or subsequent recall of a word list. Comparing those participants in Experiment 1 who chewed gum at the learning or the recall phases showed that chewing gum at initial learning was associated with superior recall. In addition, chewing gum led to context-dependent effects as a switch between gum and no gum (or no gum and gum) between learning and recall led to poorer performance. Experiment 2 provided evidence that sucking gum was sufficient to induce some of the same effects as chewing.
Static postural control has been demonstrated to link with psychological state. However, the effect of psychological state on dynamic postural control remains unclear. In this study, we examined the effect of mood state on anticipatory postural adjustment (APA), one of the most important functions for dynamic postural control. Fourteen healthy male subjects performed unilateral arm elevation tasks after completing a Profile of Mood States (POMS) questionnaire. Mood state measured by POMS and the latency or amplitude of the APA in the ventral muscles (rectus femoris, tibialis anterior) of the lower limb showed significant negative correlations. The correlation between the mood state and APA amplitude in the soleus was found to be significantly positive. There were significant negative correlations between the mood state and reaction-time. These findings suggest that it is possible that dynamic postural control is affected by mood state.
The present study examined, in children aged 4-11 and in adults, the postural control modifications when attention was oriented voluntary on postural sway. Since (1) there are less attentional resources in children than in adults, (2) the selective attention processing improves with age, i.e., children use a different strategy to focus their attention than adults, and (3) adults' postural stability decreases when attention is focused on postural sway, we hypothesized that postural stability was less affected in children than in adults when attention was focused on postural sway. Fourty four children aged 4- to 11-year-old and 11 adults participated in the experiments. The postural control task was executed in a Romberg position. Two experimental conditions were presented to the subjects, (1) to look at a video on a TV screen without instruction about the posture, and (2) to fixate a cross placed at the center of the TV screen with the instruction to remain as stable as possible. Postural performance was measured by means of a force platform. Results from this study (1) confirmed a non-monotonic improvement of postural stability during the ontogenetic period without reaching the adults' level at the age of 11, (2) suggested that children, aged 4-11, are able to focus their attention on the control of posture, and (3) showed that the automatic control of posture increases postural stability since the age of 4.
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