Significant Increase In Muscle Activity Research Articles

Neuromuscular Rehabilitation of the Brachioradialis Muscle after Distal Radius Fracture in Two Professional Soccer Players Using Electromyographic Biofeedback

The use of electromyographic biofeedback (EMG-BF) in the rehabilitation of injuries has been widely referenced in the psychological literature. However, despite some pioneering work in the field of sports, its use in the rehabilitation of sports injuries has hardly been explored. A case of two professional soccer players who each suffered a distal radius fracture is presented here. Parallel to the rehabilitation plan established by medical services, an intervention strategy using EMG-BF was established. An EMG-BF intervention was performed on the brachioradialis muscle with the aim of improving the voluntary control of its electromyographic activity. The study protocol was registered with the identifier NCT05376072. An ABA design was used. In each session, a pre- and postline was recorded to determine the EMG gain acquired at each point of the session. After six sessions, the intervention was terminated. One more follow-up session was performed. The results obtained indicated the efficacy of the intervention; a statistically significant increase in muscle activity in the brachioradialis muscle was observed.

Immediate Effect of a Comprehensive Foot Mobility and Strengthening Treatment on Ankle Muscle Activation in Children with Spastic Diplegia

Foot mobility and strengthening treatment (FMST) is a routinely practiced management strategy in musculoskeletal rehabilitation to improve ankle and foot alignment and muscle function, which prevents joint deformities. The FMST may contribute to improvements in foot alignment and muscle function in children with cerebral palsy (CP). However, treatment influence on muscle imbalances and strength in children with spastic diplegic CP is not yet documented. The aim of the study was to determine the effect of FMST on tibialis anterior (TA), medial gastrocnemius (MG), peroneus longus (PL), and soleus muscle activity using electromyography (EMG) in children with spastic diplegic CP. Twenty children with spastic diplegia (mean age: 7.4 years) with GMFCS levels I, II and III were included in this pre and post-experimental (preliminary) study. Muscle activation of TA, MG, PL, and soleus was recorded using surface EMG in a standing position before and after providing the intervention. Muscle activation in RMS-EMG (mV) was calculated. Findings showed a significant increase in muscle activation of TA, MG, and PL in standing position following the intervention. The increase in soleus muscle activation in standing was not statistically significant. We hypothesized that FMST could alter the muscle recruitment pattern. Our findings showed immediate improvement in muscle activation after the intervention. Future studies should consider its carryover effect on motor performance and gait using functional outcomes.

Influence of smartphone game play on head flexion angle, muscle activity, and load at C7 among adolescents.

Smartphones cause physiological problems due to inappropriate postures and extensive usage. India, being the second leading country with the highest number of smartphone users (492 million in 2021), has witnessed a significant rise in smartphone-related musculoskeletal disorders (MSD). This study compared the effects of 60-min smartphone gameplay on head flexion angle, muscle activity, and loads at C7 on Indian adolescents. A subjective assessment was conducted on 1659 participants, of which, 40 young male adults aged between 20-28 years performed the experimental trial. Muscle (Sternocleidomastoid) activity, head flexion angle, and load acting at the neck (C7) were analyzed through postural assessment, pre-and post-subjective analysis. Participants maintained an average of 28.46°±4.04° head flexion angle for more than 43 min (71%) in an hour while performing the task. The muscle activity increased to 23% (p < 0.001) of MVC at the end of the task compared to the beginning. The results indicated a significant increase in muscle activity (1.61 times), spinal loads (4.6 times) and subjective discomfort (2.9 times) after prolonged smartphone usage. It is evident that various aspects (duration, posture, content) play a vital role in smartphone-related MSD and there is a potential risk of cervical spine problems. The increased loads reduce muscle stiffness and increase intervertebral disc pressure.

A transition point: Assistance magnitude is a critical parameter when providing assistance during walking with an energy-removing exoskeleton or biomechanical energy harvester.

Researchers and engineers have developed exoskeletons capable of reducing the energetic cost of walking by decreasing the force their users' muscles are required to produce while contracting. The metabolic effect of assisting concentric and isometric muscle contractions depends, in part, on assistance magnitude. We conducted human treadmill experiments to explore the effects of assistance magnitude on the biomechanics and energetics of walking with an energy-removing exoskeleton designed to assist eccentric muscle contractions. Our results demonstrate that the assistance magnitude of an energy-removing device significantly affects the energetics, muscle activity, and biomechanics of walking. Under the moderate assistance magnitude condition, our device reduced the metabolic cost of walking below that of normal walking by 3.4% while simultaneously producing 0.29 W of electricity. This reduction in the energetic cost of walking was also associated with an 8.9% decrease in hamstring activity. Furthermore, we determined that there is an assistance magnitude threshold that, when crossed, results in the device transitioning from assisting to hindering its user. This transition is marked by significant increases in muscle activity and the metabolic cost of walking. These results could aid in the future design of exoskeletons and biomechanical energy harvesters, as well as adaptive control systems, that identify user-specific control parameters associated with minimum energy expenditure.

Adaptions in back muscle activity in long-haul truck drivers during prolonged driving with and without seat-integrated stimulation

ObjectiveThe aim of this study was to investigate the development of back muscle activity during a simulated 4.5-h truck drive with professional long-haul truck drivers and to assess the effects of a seat-integrated stimulation on muscle activity during the drive. MethodMuscle activity was compared intra-individually between a stimulation condition (with seat-integrated stimulation) and a no-stimulation condition (without seat-integrated stimulation) in a simulated driving study (N = 16). During the drive, sEMGs of the m. trapezius pars descendens, m. trapezius pars ascendens and m. erector spinae were recorded bilaterally and the RMS values of the sEMG amplitudes were analyzed. ResultsThere was a significant increase in muscle activity within 1-h driving periods (in m. trapezius pars descendens and m. trapezius pars ascendens) in both the stimulation and the no-stimulation condition but not within the whole sitting duration (in all muscles). Contrary to our expectations, the RMS values did not differ between conditions. ConclusionShort-term effects on back muscle activity of long-haul truck drivers during 1-h driving periods were found with and without the seat-integrated stimulation. However, interruptions of the driving task seemed to be sufficient to eliminate these effects. These findings on back muscle activity in long-haul drivers reveal new insights as to what affects the musculoskeletal system in prolonged driving. OutlookIn future studies, an uninterrupted driving task under real conditions should be used to investigate possible effects of prolonged driving on truck drivers’ muscle activity in general and of seat-integrated stimulation on back muscle activity in particular.

Semi-Squat Exercises with Varying Levels of Arterial Occlusion Pressure during Blood Flow Restriction Training Induce a Post-Activation Performance Enhancement and Improve Vertical Height Jump in Female Football Players.

Low-load blood flow restriction training (BFRT) has been shown to induce a significant increase in muscle activation. However, low-load BFRT to augment the post-activation performance enhancement (PAPE) has not been previously examined. This study aimed to examine the PAPE of low-intensity semi-squat exercises with varying pressure BFRT on vertical height jump performance. Twelve elite athletes from the Shaanxi Province women's football team volunteered to participate in this study for 4 weeks. Participants completed four testing sessions that included one of the following at random: (1) non-BFRT, (2) 50% arterial occlusion pressure (AOP), (3) 60% AOP, or (4) 70% AOP. Muscle activity of the lower thigh muscles was recorded using electromyography (EMG). Jump height, peak power output (PPO), vertical ground reaction forces (vGRF), and rate of force development (RFD) were recorded for four trials. Two-factor repeated measures analysis of variance (ANOVA) showed that semi-squat with varying pressure BFRT had a significant impact on the measured muscle EMG amplitude and MF value of vastus medialis, vastus lateralis, rectus femoris, and biceps femoris (P < 0.05), and MF value decreased with increasing pressure. Muscle activation (EMG amplitude) did not change further. The EMG amplitude of the gluteus maximus was significantly decreased by semi-squat training with different pressures (P < 0.05), while that of the gluteus maximus muscle was gradually increased by non-BFR with semi-squat training (P > 0.05). The 50% and 60% AOP BFRTs significantly increased jump height, peak power, and force increase rate (RFD) after 5 min and 10 min of rest (P < 0.05). This study further confirmed that low-intensity BFRT can significantly increase lower limb muscle activation, induce PAPE, and improve vertical height jump in female footballers. In addition, 50% AOP continuous BFRT is recommended for warm-up activities.

Visual feedback-dependent modulation of arousal, postural control, and muscle stretch reflexes assessed in real and virtual environments.

The mechanisms regulating neuromuscular control of standing balance can be influenced by visual sensory feedback and arousal. Virtual reality (VR) is a cutting-edge tool for probing the neural control of balance and its dependence on visual feedback, but whether VR induces neuromodulation akin to that seen in real environments (eyes open vs. closed or ground level vs. height platform) remains unclear. Here we monitored 20 healthy young adults (mean age 23.3 ± 3.2 years; 10 females) during four conditions of quiet standing. Two real world conditions (eyes open and eyes closed; REO and REC) preceded two eyes-open virtual 'low' (ground level; VRL) and 'high' (14 m height platform; VRH) conditions. We measured arousal via electrodermal activity and psychosocial questionnaires rating perceived fear and anxiety. We recorded surface electromyography over the right soleus, medial gastrocnemius, and tibialis anterior, and performed force plate posturography. As a proxy for modulations in neural control, we assessed lower limb reflexive muscle responses evoked by tendon vibration and electrical stimulation. Physiological and perceptual indicators of fear and anxiety increased in the VRH condition. Background soleus muscle activation was not different across conditions; however, significant increases in muscle activity were observed for medial gastrocnemius and tibialis anterior in VRH relative to REO. The mean power frequency of postural sway also increased in the VRH condition relative to REO. Finally, with a fixed stimulus level across conditions, mechanically evoked reflexes remained constant, while H-reflex amplitudes decreased in strength within virtual reality. Notably, H-reflexes were lower in the VRL condition than REO, suggesting that these ostensibly similar visual environments produce different states of reflexive balance control. In summary, we provide novel evidence that VR can be used to modulate upright postural control, but caution that standing balance in analogous real and virtual environments may involve different neural control states.

Effect of Pulsed Electromagnetic Fields (PEMFs) on Muscular Activation during Cycling: A Single-Blind Controlled Pilot Study.

PEMF stimulation results in a higher O2 muscle supply during exercise through increased O2 release and uptake. Given the importance of oxygen uptake in sport activity, especially in aerobic disciplines such as cycling, we sought to investigate the influence of PEMF on muscle activity when subjects cycled at an intensity between low and severe. Twenty semi-professional cyclists performed a constant-load exercise with randomized active (ON) or inactive (OFF) PEMF stimulation. Each subject started the recording session with 1 min of cycling without load (warm-up), followed by an instantaneous increase in power, as the individualized workload (constant-load physical effort). PEMF loops were applied on the vastus medialis and biceps femoris of the right leg. We recorded the electromyographic activity from each muscle and measured blood lactate prior the exercise and during the constant-load physical effort. PEMF stimulation caused a significant increase in muscle activity in the warm-up condition when subjects cycled without load (p < 0.001). The blood lactate concentration was higher during PEMF stimulation (p < 0.001), a possible consequence of PEMF's influence on glycolytic metabolism. PEMF stimulation augmented the activity and the metabolism of muscular fibers during the execution of physical exercise. PEMF stimulation could be used to raise the amplitude of muscular responses to physical activity, especially during low-intensity exercise.

Sensory Texture and Mastication Physics of Multi-Phase Meat Products

Food products often consist of several phases. Comminuted meat products, for example, are multiphase systems consisting of structured meat particles and unstructured batter-like substance. To develop and understand the processing of these products, it is important to understand the sensory and mechanical perception principles. To this end, two-phase food prototypes consisting of mixtures of ground beef and beef batter were prepared and subjected to sensory, texture, and oral processing analysis. The oral processing analysis focused on the biomechanical data of the chewing process, namely the kinematics of jaw movement and electromyographic activity. The ground meat served as the anisotropic phase and the meat dough as the isotropic phase. A significant increase in muscle activity, duration per bite, and occlusion time with increasing proportion of fibrous particles was demonstrated (p &lt; 0.05). In contrast, a higher proportion of isotropic substance resulted in significantly higher amplitudes of jaw movement and faster jaw kinetics (p &lt; 0.05). In mixed regimes, the system responded mainly according to the dominant phase, with sensory or mechanical response changing at a critical point. In combination with texture and sensory data, a holistic characterization of the food models could be performed.

Assessment of the Speed and Power of Push-Ups Performed on Surfaces with Different Degrees of Instability.

(I) Training in unstable conditions, with different elements, platforms, or situations, has been used because there is a significant increase in muscle activation, balance, proprioception, and even sports performance. However, it is not known how the devices used are classified according to performance variables, nor the differences according to instability experience. (II) This study aims to analyze the differences in power and speed in push-ups with different situations of instability in trained and untrained male subjects. Power and speed in push-up exercise were analyzed in 26 untrained and 25 trained participants in 6 different situations (one stable and five unstable) (1) stable (PS), (2) monopodal (PM), (3) rings (PR), (4) TRX® (PT), (5) hands-on Bosu® (PH) (6) feet on Bosu® (PF). The variables were analyzed using a linear position transducer. (III) The best data were evidenced with PS, followed by PR, PM, PT, PH and PF. The trained subjects obtained better results in all the conditions analyzed in mean and maximum power and speed values (p < 0.001). The decrease in these variables was significantly greater in the untrained subjects than in the trained subjects in the PR situation (8% and 18% respectively). In PF there were differences between groups (p < 0.001), reaching between 32-46% in all variables. The difference between the two groups was notable, varying between 12-58%. (IV) The results showed a negative and progressive influence of instability on power and speed in push-ups. This suggests that instability should be adapted to the subject's experience and is not advisable in untrained subjects who wish to improve power.

Effect of incremental intensities on the spinal morphology and core muscle activation in competitive cyclists

ABSTRACT Cycling is a sport where cyclists predominantly adopt a sitting posture, with the trunk tilted forward. This posture requires a high volume of training and duration in several intensities of effort. This study aims to: 1) evaluate the behaviour of the thoracic and lumbar spine flexion and sacral inclination in the sagittal plane, the thoracic and lumbar spine flexion in the frontal plane, and the trunk torsion in the transverse plane; 2) compare the activation of the core muscles as the intensity of effort increases during an incremental test in cycling, and 3) identify which core muscle has a greater activation in each intensity zone. The spinal posture and the activation of the eight core muscles were evaluated in twelve competitive cyclists during incremental cycling intensities. Thoracic and lumbar spine flexion and sacral inclination statistically increased as the intensity of effort increased (Start < VT1 < VT2 < VO2max). A significant increase in muscle activation was observed in all core muscles evaluated as the intensity increased. The rectus abdominis showed statistically significant greater muscle activation than the other core muscles evaluated. In conclusion, as the intensity of effort in cycling increases, cyclists significantly increase the thoracic and lumbar spine flexion, the sacral inclination in the sagittal plane, the thoracic and lumbar spine flexion in the frontal plane, trunk rotation in the transverse plane, as well as the activation of the core muscles.

Muscle responses during radial nerve-biased upper limb neurodynamic test in asymptomatic individuals: a cross-sectional study

ABSTRACT This laboratory cross-sectional study aimed at explore the muscle response (MR) of the upper trapezius, infraspinatus, biceps brachii and extensor carpi radialis brevis (ECRB) during the radial nerve-biased upper limb neurodynamic test (RN-ULNT) in healthy participants. Myoelectric activity was stage-by-stage recorded during two sequencing variants of the RN-ULNT: S1, in which elbow extension was the last movement; and S2, in which wrist flexion was the last movement. Final elbow and wrist joint angle and sensory response (SR) in five zones (Z1-Z5) were also registered. MR was qualitatively categorized as ‘absent’ (No-MR), ‘true’ (TMR) or ‘uneven’ (UMR). In both sequences, significant increases in muscle activity occurred mostly during shoulder abduction and elbow extension (p ≤ 0.009). Also, elbow extension but not wrist flexion increased the activity of the ECRB muscle (p ≤ 0.009). S2 showed significantly higher upper trapezius (p = 0.04) and biceps brachii (p = 0.036) muscle activity during wrist flexion, and higher report of SR in Z1 and Z4 (p < 0.001) compared to S1. Only the ECRB muscle showed significant differences in the MR type between S1 and S2 (TMR, p = 0.016; UMR, = 0,012). Our results may be useful in the assessment of upper limb musculoskeletal disorders.

The Effect of Aquabag Use on Muscle Activation in Functional Strength Training.

Although training with an aquabag (AB) has gained popularity, there is a lack of evidence of its effect. This study wanted to evaluate the effect of AB implementation on muscle activity of core and lower limb muscles during 3 functional exercises. Cross-sectional observational study. Twenty healthy subjects performed a squat, lunge, and step-up, while using a stick and an AB. Surface electromyography signals were recorded from the trunk, pelvis, and thigh muscles in the dominant leg. Linear-mixed models were used to analyze the normalized surface electromyography signals. Results demonstrated a significant increase in muscle activity of the back muscles during all 3 exercises (P < .001 to P = .003), abdominals during squat (P = .034) and step-up (P = .046), hamstrings during lunge (P = .008) and step-up (P = .008), and gluteal muscles during lunge (P < .001 and P = .010, respectively). These results indicate that an AB promotes functional strength training by demanding compensatory/additional activity of both stabilizing muscles (specifically in the core and pelvis regions) and prime movers of the lower limb. The authors recommend the use of an AB to enhance training and rehabilitation effects.

Effect of soft tissue manipulation of popliteus muscle on quadriceps muscle activity and torque production in athletes with anterior knee pain

Abstract Study aim: Popliteus is majorly associated with posterior knee pain; however, this muscle can also have an impact on anterior knee pain. The purpose of this study was to determine the effect of soft tissue manipulation of popliteus muscle on non-traumatic anterior knee pain in athletes; as the relationship between popliteus and Quadriceps muscle has not been studied/explored much. Materials and methods: In this experimental study, 15 subjects presenting with non-traumatic anterior knee pain were selected. Quadriceps muscle activity, torque production and knee pain were assessed. Followed by a single session of popliteus manipulation all the above parameters were re-assessed immediately and at 24 hours after intervention. Results: Significant reduction in pain (P &lt; 0.005) at 24 hours was observed. There was a significant increase in muscle activity of Vastus Medialis (P &lt; 0.05) and Vastus Lateralis (P &lt; 0.005) immediately after the intervention but not after 24 hours. No significant change was found in the activity of Rectus femoris and Peak torque of Quadriceps immediately after the intervention and at 24 hours. Conclusion: Soft tissue manipulation decreased knee pain and improved muscle activity. Therefore, incorporating popliteus manipulation can be effective in treatment of anterior knee pain.

Muscle recruitment patterns and saddle pressure indexes with alterations in effective seat tube angle

Alteration of the effective seat tube angle (ESTA) may affect muscle activation patterns of the lower limbs in cycling. There is conflicting evidence due to inadequate kinematic controls in previous studies. The primary aim of this study was to determine the muscle activity of seven lower limb muscles during alterations of the ESTA by altering the position of both the handlebars and saddle forwards or backwards by 3 ​cm while ensuring controlled kinematics. Secondly, to determine the effect on the saddle pressure indexes. Ten participants performed two 5 ​min electromyography (EMG) trials at 70% of peak power output (PPO) for three consecutive visits. There was a significant increase in muscle activity in the biceps femoris, gluteus maximus, and medial gastrocnemius with reductions in ESTA while a significant increase in tibialis anterior with increases in ESTA was observed. Saddle pressure indices demonstrated a significant change in frontal versus back pressure as well as mean pubic pressure with changes in ESTA. Alteration in the ESTA affects muscle activity in some, but not all of the lower limb muscles. Further research needs to be conducted to adequately understand the mechanism behind the differences in muscle activation.

Evidence for increased neuromuscular drive following spinal manipulation in individuals with subacromial pain syndrome

BackgroundThoracic spinal manipulation can improve pain and function in individuals with shoulder pain; however, the mechanisms underlying these benefits remain unclear. Here, we evaluated the effects of thoracic spinal manipulation on muscle activity, as alteration in muscle activity is a key impairment for those with shoulder pain. We also evaluated the relationship between changes in muscle activity and clinical outcomes, to characterize the meaningful context of a change in neuromuscular drive. MethodsParticipants with shoulder pain related to subacromial pain syndrome (n = 28) received thoracic manipulation of low amplitude high velocity thrusts to the lower, middle and upper thoracic spine. Electromyographic muscle activity (trapezius-upper, middle, lower; serratus anterior; deltoid; infraspinatus) and shoulder pain (11-point scale) was collected pre and post-manipulation during arm elevation, and normalized to a reference contraction. Clinical benefits were assessed using the Pennsylvania Shoulder Score (Penn) at baseline and 2–3 days post-intervention. FindingsA significant increase in muscle activity was observed during arm ascent (p = 0.002). Using backward stepwise regression analysis, a specific increase in the serratus anterior muscle activity during arm elevation explained improved Penn scores following post-manipulation (p < 0.05). InterpretationThoracic spinal manipulation immediately increases neuromuscular drive. In addition, increased serratus anterior muscle activity, a key muscle for scapular motion, is associated with short-term improvements in shoulder clinical outcomes.

Changes in the Trend of Walking Motor Control in Athletes with Anterior Cruciate Ligament Deficiency in Response to Progressive Perturbation Trainings

Background and Purpose: The beliefs are that sudden and unpredictable balance disturbance by instruments that cause mechanical perturbations can affect individuals with Anterior Cruciate Ligament Deficiency (ACLD) to reach faster and more effective recovery of knee dynamic stabilization strategies to return successfully pre-injury levels. The aim of this study was to investigate the effect of mechanical perturbation training and standard training in the process of changes in motor control during walking task in coper ACLD individuals. Methods: Thirty athletes with a unilateral rupture of the Anterior Cruciate Ligament (ACL), classified as coper, were randomly assigned to perturbation and standard training groups. Intervention training results based on comparison of scores obtained from functional tests in 4 single-leg jump tests, scores of questioners, and surface Electromyography (sEMG) tests were determined between the two groups as well as between the two healthy and ACLD limbs in each group in the walking task. Results: The perturbation training group showed a significant increase in muscle activity in both healthy and ACLD limbs with an increase in similarity index (SI) (p=0.08, ES=0.81), while in the standard training group the results were not significant (p=0.39, ES=0.39). Conclusion: Individuals in the perturbation training group achieved higher scores on all tests compared to the standard training group. This means that the perturbation training group was more mentally and physically prepared in terms of strength, coordination and symmetry between the two limbs to participate in pre-injury sports levels.

Muscle co-contraction of ankle joint in young adults in functional reach test at different distances

It has been reported that young people may be able to modulate simultaneous contraction depending on the task. The functional reach test (FRT) is widely used as a method to assess dynamic balance. Although there are several reports on the center of pressure (COP), there are few reports on muscle activity and no studies focus on muscle co-contraction during FRT at different distances. We aimed to clarify how the differences in reach distance affect the activity of the lower limb muscles by measuring COP and muscle activity during FRT at different distances. Eighteen healthy young adults performed FRT at different distances (maximum, 75%, and 50%) and measured COP and muscle activity of tibialis anterior (TA) and soleus (SOL). Postural control variables were calculated from the COP, and mean muscle activity and muscle co-contraction index (CI) were calculated from muscle activity. Each variable was compared between the reach distance conditions and the correlation between the variable was examined. Most COP variables were significantly higher as the reach distance increased. A significant increase in muscle activity and CI was similarly observed with increasing distance. There was no consistent correlation between COP variables and CI, but there was a positive correlation between TA muscle activity and CI. The results of the present study showed that the young people used task-specific strategies by modulating lower limb muscle contraction and varying the degree of simultaneous muscle contraction during reaching movements at different distances.

Developing a pain intensity prediction model using facial expression: A feasibility study with electromyography.

The automatic detection of facial expressions of pain is needed to ensure accurate pain assessment of patients who are unable to self-report pain. To overcome the challenges of automatic systems for determining pain levels based on facial expressions in clinical patient monitoring, a surface electromyography method was tested for feasibility in healthy volunteers. In the current study, two types of experimental gradually increasing pain stimuli were induced in thirty-one healthy volunteers who attended the study. We used a surface electromyography method to measure the activity of five facial muscles to detect facial expressions during pain induction. Statistical tests were used to analyze the continuous electromyography data, and a supervised machine learning was applied for pain intensity prediction model. Muscle activation of corrugator supercilii was most strongly associated with self-reported pain, and the levator labii superioris and orbicularis oculi showed a statistically significant increase in muscle activation when the pain stimulus reached subjects’ self -reported pain thresholds. The two strongest features associated with pain, the waveform length of the corrugator supercilii and levator labii superioris, were selected for a prediction model. The performance of the pain prediction model resulted in a c-index of 0.64. In the study results, the most detectable difference in muscle activity during the pain experience was connected to eyebrow lowering, nose wrinkling and upper lip raising. As the performance of the prediction model remains modest, yet with a statistically significant ordinal classification, we suggest testing with a larger sample size to further explore the variables that affect variation in expressiveness and subjective pain experience.

Electromyography of the masticatory muscles during chewing in different head and neck postures - A pilot study

ObjectivesThe objectives of this pilot study were to analyze the electromyography (EMG) activity of masseter and anterior temporalis muscles during chewing in 2 different posture conditions: natural head posture (NHP) and maximum yet comfortable forward head posture (FHP) in healthy individuals; and to compare EMG activity between subjects based on their NHP during chewing. MethodsFifteen subjects participated. Sagittal head posture in sitting position was clinically assessed using a plumb line. Participants were classified as having FHP or upright head posture (UP). Surface EMG was used to evaluate superficial masseter and anterior temporalis bilaterally during chewing in NHP and FHP. Three trials with five chewing cycles were recorded. EMG data were normalized using a maximum voluntary contraction. An independent t-test was used to calculate differences between sides. If no differences were found, both sides were analyzed together. To analyze differences between the 2 conditions, a paired t-test was used. Independent t-test was used to calculate difference between subjects with UP and FHP. ResultsA significant increase in muscle activity was found for masseter muscle in the FHP condition. No differences were found in muscle activity in natural head position by posture classification. A trend of increased activity was observed for masseter and temporalis muscles during chewing in FHP. ConclusionHead and neck posture was found to influence masticatory muscle activity during the function of chewing. The results of this study may help clinicians to better understand the association between head and neck posture alterations with masticatory muscles related disorders.