PREPARATORY EMG ACTIVITY REVEALS A RAPID ADAPTATION PATTERN IN HUMANS PERFORMING LANDING MOVEMENTS IN BLINDFOLDED CONDITION

The main questions addressed in this work were whether and how adaptation to suppression of visual information occurs in a free-fall paradigm, and the extent to which vision availability influences the control of landing movements. The prelanding modulation of EMG timing and amplitude of four lower-limb muscles was investigated. Participants performed six consecutive drop-landings from four different heights in two experimental conditions: with and without vision. Experimental design precluded participants from estimating the height of the drop. Since cues provided by proprioceptive and vestibular information acquired during the first trials were processed, the nervous system rapidly adapted to the lack of visual information, and hence produced a motor output (i.e., prelanding EMG modulation) similar to that observed when performing the activity with vision available.

Electromyographic Study in Patients With Surgically Treated Facial Fractures

This study, using surface electromyography, analyzed the activity of the masseter muscles of 30 patients with facial bone fractures that were surgically treated. Evaluations were made before surgery and in the 7th, 30th, and 60th days after surgery. The value of each measure and the average of 3 maximum voluntary isometric contractions lasting 5 seconds each were registered, and statistical analyses were performed. Patients had a mean age of 31 years and an average of 1.33 fractures. They were grouped according to the type of fracture as follows: mandibular (50%), zygomatic complex (33%), maxilla (10%), and associated fractures (6.7%). There was a lower masseter activity in the preoperative period, when compared with normal values in all groups of fractures. There was a sharp drop in the masseter activity in the postoperative period of 7 days, and all groups showed recovery of activity in 60 days but still below the normal value referenced in the literature. The mean values of the masseter activity, in descending order, were from the zygomatic complex, mandibular, maxillary, and associated fractures. The unilateral mandibular fractures showed higher values than the bilateral fractures in most of the evaluations. There was a highly significant difference in the comparison of the evolution of the masseter activity on both sides, for mandibular and zygomatic complex fractures, and the pairwise comparison showed significant difference between most groups. It was concluded that facial fractures and surgical procedures had negative effects in the muscle activity as observed using electromyography.

Effects of replica running shoes upon external forces and muscle activity during running

Twelve participants ran (9 km . h(-1)) to test two types of running shoes: replica and original shoes. Ground reaction force, plantar pressure and electromyographic activity were recorded. The shoes were tested randomly and on different days. Comparisons between the two experimental conditions were made by analysis of variance (ANOVA) test (P <= 0.05). The time to first peak, loading rate of the first peak and impulse of the first 75 ms of stance were significantly different between the shoes (P <= 0.05), revealing an increase of impact forces for the replica shoes. The peak plantar pressure values were significantly higher (P <= 0.05) when wearing replica shoes. During running, the contact area was significantly smaller (P <= 0.05) for the replica shoe. The electromyographic activity of the analysed muscles did not show changes between the two shoes in running. These findings suggest that the use of replica running shoes can increase the external load applied to the human body, but may not change the muscle activity pattern during locomotion. This new mechanical situation may increase the risk of injuries in these movements.

Effect of a rocker non-heeled shoe on EMG and ground reaction forces during gait without previous training

Unstable shoes have been designed to promote "natural instability" and during walking they should simulate barefoot gait, enhancing muscle activity and, thus, attributing an advantage over regular tennis shoes. Recent studies showed that, after special training on the appropriate walking pattern, the use of the Masai Barefoot Technology (MBT) shoe increases muscle activation during walking. Our study presents a comparison of muscle activity as well as horizontal and vertical forces during gait with the MBT, a standard tennis shoe and barefoot walking of healthy individuals without previous training. These variables were compared in 25 female subjects and gait conditions were compared using ANOVA repeated measures (effect size:0.25). Walking with the MBT shoe in this non-instructed condition produced higher vertical forces (first vertical peak and weight acceptance rate) than walking with a standard shoe or walking barefoot, which suggests an increase in the loads received by the musculoskeletal system, especially at heel strike. Walking with the MBT shoe did not increase muscle activity when compared to walking with the standard shoe. The barefoot condition was more effective than the MBT shoe at enhancing muscle activation. Therefore, in healthy individuals, no advantage was found in using the MBT over a standard tennis shoe without a special training period. Further studies using the MBT without any instruction over a longer period are needed to evaluate if the higher loads observed in the present study would return to their baseline values after a period of adaptation, and if the muscle activity would increase over time. (C) 2012 Elsevier B.V. All rights reserved.

Análise da reprodutibilidade de parâmetros no domínio da frequência do sinal EMG utilizados na caracterização da fadiga muscular localizada

O objetivo deste estudo foi analisar a reprodutibilidade de parâmetros no domínio da frequência do sinal eletromiográfico (EMG) utilizados na caracterização da fadiga muscular localizada. Quinze sujeitos do sexo masculino foram submetidos a um teste de fadiga baseado na extensão isométrica de joelho, sendo realizados em três momentos distintos com intervalos de sete dias. Para avaliar a reprodutibilidade dos dados entres os testes calculou-se o coeficiente de correlação intraclasse (CCI) para a frequência mediana (Fmed) no tempo total de exercício (FmedT), para a Fmed obtida a cada 10% do tempo de exercício (Fmed10%) e para as potências das bandas de frequência, obtidas da divisão do espectro de potência a cada 20 Hz. Os resultados demonstraram: (1) boa reprodutibilidade para a FmedT; (2) boa reprodutibilidade para a Fmed10%; e (3) maior variação no sinal EMG nas bandas de 20 a 120 Hz, no qual se destacam as bandas de 20-40 Hz e de 40-60 Hz, demonstrando maior sensibilidade ao processo de fadiga muscular. Conclui-se que a Fmed é uma variável que apresenta boa reprodutibilidade e que a análise fragmentada do espectro de potência, por meio das bandas de frequência, demonstrou-se sensível as variações que ocorrem no sinal EMG durante a instalação do processo de fadiga, tendo potencial para se tornar um novo método para a caracterização da fadiga muscular localizada.

The effect of hip abduction on the EMG activity of vastus medialis obliquus, vastus lateralis longus and vastus lateralis obliquus in healthy subjects

Abstract Study design Controlled laboratory study. Objectives The purposes of this paper were to investigate (d) whether vastus medialis obliquus (VMO), vastus lateralis longus (VLL) and vastus lateralis obliquus (VLO) EMG activity can be influenced by hip abduction performed by healthy subjects. Background Some clinicians contraindicate hip abduction for patellofemoral patients (with) based on the premise that hip abduction could facilitate the VLL muscle activation leading to a VLL and VMO imbalance Methods and measures Twenty-one clinically healthy subjects were involved in the study, 10 women and 11 men (aged X = 23.3 ± 2.9). The EMG signals were collected using a computerized EMG VIKING II, with 8 channels and three pairs of surface electrodes. EMG activity was obtained from MVIC knee extension at 90° of flexion in a seated position and MVIC hip abduction at 0° and 30° with patients in side-lying position with the knee in full extension. The data were normalized in the MVIC knee extension at 50° of flexion in a seated position, and were submitted to ANOVA test with subsequent application of the Bonferroni multiple comparisons analysis test. The level of significance was defined as p ≤ 0.05. Results The VLO muscle demonstrated a similar pattern to the VMO muscle showing higher EMG activity in MVIC knee extension at 90° of flexion compared with MVIC hip abduction at 0° and 30° of abduction for male (p < 0.0007) and MVIC hip abduction at 0° of abduction for female subjects (p < 0.02196). There were no statistically significant differences in the VLL EMG activity among the three sets of exercises tested. Conclusion The results showed that no selective EMG activation was observed when comparison was made between the VMO, VLL and VLO muscles while performing MVIC hip abduction at 0° and 30° of abduction and MVIC knee extension at 90° of flexion in both male and female subjects. Our findings demonstrate that hip abduction do not facilitated VLL and VLO activity in relation to the VMO, however, this study included only healthy subjects performing maximum voluntary isometric contraction contractions, therefore much remains to be discovered by future research

Atividade muscular da mastigação na anquilose temporomandibular

Purpose: due to the presence of major masticatory dysfunction in patients with temporomandibular joint (TMJ) ankylosis, this study analyzed mouth opening and EMG activity of masticatory muscles in order to detect changes in these parameters after surgical release of mandible ankylosis. Method: in 7 patients with temporomandibular ankylosis, between 7 and 30 years (median = 9 years), the distance was measured as interincisal maximum active (DIMA) and we recorded the electromyographic activity (EMG) of masseter and temporal muscles during voluntary isometric contraction (VIC) and chewing, comparing the data before and after surgery using the Wilcoxon test. Results: higher values were observed for DIMA after surgery (p=0.0277), the asymmetry index showed no difference between the two evaluated periods for both studied muscles, the values of the EMG during VIC decreased after surgery for the right (p=0.0179) and left (p=0.0179) masseter but not for the temporal muscle, there were no changes in EMG values for the studied muscles during mastication. Conclusion: the surgical release of TMJ ankylosis resulted in an increase of mouth opening and decreased amplitude of action potentials generated during maximum isometric voluntary contraction of the masseter muscle on both sides, this did not change the asymmetry index of the masseter and temporal as well as the electromyographic activity of the temporal muscle bilaterally during isometric contraction and masseter and temporal muscles during mastication.

Comparação do sinal EMG e das características da passada em diferentes protocolos de corrida incremental

O objetivo do presente estudo foi comparar o sinal eletromiográfi co, a frequência e a amplitude de passada entre diferentes intensidades de corrida: 60%, 80% e 100% da velocidade máxima em dois protocolos incrementais. Participaram deste estudo 11 corredores do sexo masculino. Os protocolos de corrida foram realizados com velocidades iniciais de 10 km.hr-1, com incrementos de 1 km.hr-1 a cada três minutos até a exaustão, que diferiram em relação ao intervalo entre cada estágio incremental: 30 e 120 segundos. Foram analisados valores RMS dos músculos iliocostal lombar, reto femoral, vasto lateral, vasto medial, bíceps femoral, tibial anterior, e gastrocnêmio, e a amplitude e frequência de passada. Os valores RMS mostraram aumento entre as intensidades para quase todos os músculos, e não foram influenciados pelo tipo de protocolo utilizado para maioria dos músculos. A frequência e amplitude de passada apresentaram contribuições percentuais diferenciadas para o aumento da velocidade de corrida.

Vibration as a method for muscular stimulation

Human reactions to vibration have been extensively investigated in the past. Vibration, as well as whole-body vibration (WBV), has been commonly considered as an occupational hazard for its detrimental effects on human condition and comfort. Although long term exposure to vibrations may produce undesirable side-effects, a great part of the literature is dedicated to the positive effects of WBV when used as method for muscular stimulation and as an exercise intervention. Whole body vibration training (WBVT) aims to mechanically activate muscles by eliciting neuromuscular activity (muscle reflexes) via the use of vibrations delivered to the whole body. The most mentioned mechanism to explain the neuromuscular outcomes of vibration is the elicited neuromuscular activation. Local tendon vibrations induce activity of the muscle spindle Ia fibers, mediated by monosynaptic and polysynaptic pathways: a reflex muscle contraction known as the Tonic Vibration Reflex (TVR) arises in response to such vibratory stimulus. In WBVT mechanical vibrations, in a range from 10 to 80 Hz and peak to peak displacements from 1 to 10 mm, are usually transmitted to the patient body by the use of oscillating platforms. Vibrations are then transferred from the platform to a specific muscle group through the subject body. To customize WBV treatments, surface electromyography (SEMG) signals are often used to reveal the best stimulation frequency for each subject. Use of SEMG concise parameters, such as root mean square values of the recordings, is also a common practice; frequently a preliminary session can take place in order to discover the more appropriate stimulation frequency. Soft tissues act as wobbling masses vibrating in a damped manner in response to mechanical excitation; Muscle Tuning hypothesis suggest that neuromuscular system works to damp the soft tissue oscillation that occurs in response to vibrations; muscles alters their activity to dampen the vibrations, preventing any resonance phenomenon. Muscle response to vibration is however a complex phenomenon as it depends on different parameters, like muscle-tension, muscle or segment-stiffness, amplitude and frequency of the mechanical vibration. Additionally, while in the TVR study the applied vibratory stimulus and the muscle conditions are completely characterised (a known vibration source is applied directly to a stretched/shortened muscle or tendon), in WBV study only the stimulus applied to a distal part of the body is known. Moreover, mechanical response changes in relation to the posture. The transmissibility of vibratory stimulus along the body segment strongly depends on the position held by the subject. The aim of this work was the investigation on the effects that the use of vibrations, in particular the effects of whole body vibrations, may have on muscular activity. A new approach to discover the more appropriate stimulus frequency, by the use of accelerometers, was also explored. Different subjects, not affected by any known neurological or musculoskeletal disorders, were voluntarily involved in the study and gave their informed, written consent to participate. The device used to deliver vibration to the subjects was a vibrating platform. Vibrations impressed by the platform were exclusively vertical; platform displacement was sinusoidal with an intensity (peak-to-peak displacement) set to 1.2 mm and with a frequency ranging from 10 to 80 Hz. All the subjects familiarized with the device and the proper positioning. Two different posture were explored in this study: position 1 - hack squat; position 2 - subject standing on toes with heels raised. SEMG signals from the Rectus Femoris (RF), Vastus Lateralis (VL) and Vastus medialis (VM) were recorded. SEMG signals were amplified using a multi-channel, isolated biomedical signal amplifier The gain was set to 1000 V/V and a band pass filter (-3dB frequency 10 - 500 Hz) was applied; no notch filters were used to suppress line interference. Tiny and lightweight (less than 10 g) three-axial MEMS accelerometers (Freescale semiconductors) were used to measure accelerations of onto patient’s skin, at EMG electrodes level. Accelerations signals provided information related to individuals’ RF, Biceps Femoris (BF) and Gastrocnemius Lateralis (GL) muscle belly oscillation; they were pre-processed in order to exclude influence of gravity. As demonstrated by our results, vibrations generate peculiar, not negligible motion artifact on skin electrodes. Artifact amplitude is generally unpredictable; it appeared in all the quadriceps muscles analysed, but in different amounts. Artifact harmonics extend throughout the EMG spectrum, making classic high-pass filters ineffective; however, their contribution was easy to filter out from the raw EMG signal with a series of sharp notch filters centred at the vibration frequency and its superior harmonics (1.5 Hz wide). However, use of these simple filters prevents the revelation of EMG power potential variation in the mentioned filtered bands. Moreover our experience suggests that the possibility of reducing motion artefact, by using particular electrodes and by accurately preparing the subject’s skin, is not easily viable; even though some small improvements were obtained, it was not possible to substantially decrease the artifact. Anyway, getting rid of those artifacts lead to some true EMG signal loss. Nevertheless, our preliminary results suggest that the use of notch filters at vibration frequency and its harmonics is suitable for motion artifacts filtering. In RF SEMG recordings during vibratory stimulation only a little EMG power increment should be contained in the mentioned filtered bands due to synchronous electromyographic activity of the muscle. Moreover, it is better to remove the artifact that, in our experience, was found to be more than 40% of the total signal power. In summary, many variables have to be taken into account: in addition to amplitude, frequency and duration of vibration treatment, other fundamental variables were found to be subject anatomy, individual physiological condition and subject’s positioning on the platform. Studies on WBV treatments that include surface EMG analysis to asses muscular activity during vibratory stimulation should take into account the presence of motion artifacts. Appropriate filtering of artifacts, to reveal the actual effect on muscle contraction elicited by vibration stimulus, is mandatory. However as a result of our preliminary study, a simple multi-band notch filtering may help to reduce randomness of the results. Muscle tuning hypothesis seemed to be confirmed. Our results suggested that the effects of WBV are linked to the actual muscle motion (displacement). The greater was the muscle belly displacement the higher was found the muscle activity. The maximum muscle activity has been found in correspondence with the local mechanical resonance, suggesting a more effective stimulation at the specific system resonance frequency. Holding the hypothesis that muscle activation is proportional to muscle displacement, treatment optimization could be obtained by simply monitoring local acceleration (resonance). However, our study revealed some short term effects of vibratory stimulus; prolonged studies should be assembled in order to consider the long term effectiveness of these results. Since local stimulus depends on the kinematic chain involved, WBV muscle stimulation has to take into account the transmissibility of the stimulus along the body segment in order to ensure that vibratory stimulation effectively reaches the target muscle. Combination of local resonance and muscle response should also be further investigated to prevent hazards to individuals undergoing WBV treatments.

Implementation of a VLSI amplifier interfaced with biomedical sensors for ultra wide band data transmission

This thesis presents a CMOS Amplifier with High Common Mode rejection designed in UMC 130nm technology. The goal is to achieve a high amplification factor for a wide range of biological signals (with frequencies in the range of 10Hz-1KHz) and to reject the common-mode noise signal. It is here presented a Data Acquisition System, composed of a Delta-Sigma-like Modulator and an antenna, that is the core of a portable low-complexity radio system; the amplifier is designed in order to interface the data acquisition system with a sensor that acquires the electrical signal. The Modulator asynchronously acquires and samples human muscle activity, by sending a Quasi-Digital pattern that encodes the acquired signal. There is only a minor loss of information translating the muscle activity using this pattern, compared to an encoding technique which uses astandard digital signal via Impulse-Radio Ultra-Wide Band (IR-UWB). The biological signals, needed for Electromyographic analysis, have an amplitude of 10-100μV and need to be highly amplified and separated from the overwhelming 50mV common mode noise signal. Various tests of the firmness of the concept are presented, as well the proof that the design works even with different sensors, such as Radiation measurement for Dosimetry studies.

Effect of selective dorsal rhizotomy on gait in children with bilateral spastic paresis: kinematic and EMG-pattern changes

Selective dorsal rhizotomy (SDR) is an effective treatment for reducing spasticity and improving gait in children with spastic cerebral palsy. Data concerning muscle activity changes after SDR treatment are limited.

Electromyographic activity of the cervical flexor muscles in patients with temporomandibular disorders while performing the craniocervical flexion test: a cross-sectional study

Most patients with temporomandibular disorders (TMD) have been shown to have cervical spine dysfunction. However, this cervical dysfunction has been evaluated only qualitatively through a general clinical examination of the cervical spine.

The significance of the sympathetic nervous system in the pathophysiology of periodic leg movements in sleep

STUDY OBJECTIVES: Periodic leg movements in sleep (PLMS) are frequently accompanied by arousals and autonomic activation, but the pathophysiologic significance of these manifestations is unclear. DESIGN: Changes in heart rate variability (HRV), HRV spectra, and electroencephalogram (EEG) spectra associated with idiopathic PLMS were compared with changes associated with isolated leg movements and respiratory-related leg movements during sleep. Furthermore, correlations between electromyographic activity, HRV changes, and EEG changes were assessed. SETTING: Sleep laboratory. PATIENTS: Whole-night polysomnographic studies of 24 subjects fulfilling the criteria of either periodic leg movements disorder (n = 8), obstructive sleep apnea syndrome (n = 7), or normal polysomnography (n = 9) were used. MEASUREMENTS AND RESULTS: Spectral HRV changes started before all EEG changes and up to 6 seconds before the onset of all types of leg movements. An initial weak autonomic activation was followed by a sympathetic activation, an increase of EEG delta activity, and finally a progression to increased higher-frequency EEG rhythms. After movement onset, HRV indicated a vagal activation, and, the EEG, a decrease in spindle activity. Sympathetic activation, as measured by HRV spectra, was greater for PLMS than for all other movement types. In EEG, gamma synchronization began 1 to 2 seconds earlier for isolated leg movements and respiratory-related leg movements than for PLMS. Significant correlations were found between autonomic activations and electromyographic activity, as well as between autonomic activations and EEG delta activity, but not between higher-frequency EEG rhythms and EMG activity or HRV changes. CONCLUSIONS: These results suggest a primary role of the sympathetic nervous system in the generation of PLMS.

Feasibility of Using EMG for Early Detection of the Facial Nerve During Robotic Direct Cochlear Access

HYPOTHESIS Facial nerve monitoring can be used synchronous with a high-precision robotic tool as a functional warning to prevent of a collision of the drill bit with the facial nerve during direct cochlear access (DCA). BACKGROUND Minimally invasive direct cochlear access (DCA) aims to eliminate the need for a mastoidectomy by drilling a small tunnel through the facial recess to the cochlea with the aid of stereotactic tool guidance. Because the procedure is performed in a blind manner, structures such as the facial nerve are at risk. Neuromonitoring is a commonly used tool to help surgeons identify the facial nerve (FN) during routine surgical procedures in the mastoid. Recently, neuromonitoring technology was integrated into a commercially available drill system enabling real-time monitoring of the FN. The objective of this study was to determine if this drilling system could be used to warn of an impending collision with the FN during robot-assisted DCA. MATERIALS AND METHODS The sheep was chosen as a suitable model for this study because of its similarity to the human ear anatomy. The same surgical workflow applicable to human patients was performed in the animal model. Bone screws, serving as reference fiducials, were placed in the skull near the ear canal. The sheep head was imaged using a computed tomographic scanner and segmentation of FN, mastoid, and other relevant structures as well as planning of drilling trajectories was carried out using a dedicated software tool. During the actual procedure, a surgical drill system was connected to a nerve monitor and guided by a custom built robot system. As the planned trajectories were drilled, stimulation and EMG response signals were recorded. A postoperative analysis was achieved after each surgery to determine the actual drilled positions. RESULTS Using the calibrated pose synchronized with the EMG signals, the precise relationship between distance to FN and EMG with 3 different stimulation intensities could be determined for 11 different tunnels drilled in 3 different subjects. CONCLUSION From the results, it was determined that the current implementation of the neuromonitoring system lacks sensitivity and repeatability necessary to be used as a warning device in robotic DCA. We hypothesize that this is primarily because of the stimulation pattern achieved using a noninsulated drill as a stimulating probe. Further work is necessary to determine whether specific changes to the design can improve the sensitivity and specificity.