Electromyographic Amplitude Research Articles

Effects of Trigger Point Dry Needling on Strength Measurements and Activation Levels of the Gluteus Medius: A Quasi-Experimental Randomized Control Study.

Latent trigger points have been identified as a source of impaired muscle function giving rise to a reduction in force production and alterations in muscle activation patterns and movement efficiency. There is limited investigation into the effectiveness of a treatment in reducing these clinical manifestations. To investigate whether the application of trigger point dry needling (TDN) to latent trigger points within the gluteus medius musculature affected strength measurements and muscle activation levels immediately following intervention. Quasi experimental, single group, pretest-posttest, randomized control study. A control and an intervention side were randomly assigned for each participant (N = 39). Hand held dynamometer (HHD) force measurements and raw surface electromyography (sEMG) amplitude readings were recorded during maximal volitional isometric contractions of the gluteus medius in two separate positions before and after application of TDN. Comparison of within and between group data were conducted. A statistically significant interaction between time (pre-TDN to post-TDN) and groups (intervention side and control side), p < 0.001 was found for HHD measurements in both positions. Post hoc analysis revealed a statistically significant difference (p < 0.001) for all comparisons in the side lying neutral (SL0) position, while statistically significant differences (p < 0.001) were found for pre and post-TDN measurements within intervention side as well as between the intervention and control side for post-TDN measurements in the side lying internal rotation (SLIR) position. For sEMG amplitude measurements, statistically significant differences were found only in the SL0 position for within group comparisons on the intervention side (p = 0.009) and for between group comparisons for post-TDN measurements (p = 0.002). Application of TDN to latent trigger points within the gluteus medius can significantly increase gluteus muscle force production immediately following intervention while reducing the level of muscle activation required during contraction. Level 2.

Standardized Intraoperative Neuromonitoring Procedure is Feasible in Transoral Endoscopic Thyroidectomy.

Intraoperative neuromonitoring in thyroid surgeries has become popular, but the standardized manner of intraoperative neuromonitoring during transoral endoscopic thyroidectomy vestibular approach (TOETVA) is not well established. This study evaluated the feasibility of using a standardized intraoperative neuromonitoring method for TOETVA. Medical records of consecutive patients who underwent TOETVA with intraoperative neuromonitoring were retrospectively reviewed. Patients were positioned before intubation to prevent tube migration, then intubated using video laryngoscopy. The electromyography amplitudes of the vagal nerves and the recurrent laryngeal nerves were checked before (V1, R1) and after (V2, R2) thyroid resection. V1 and V2 signals were evaluated using a long ball tip stimulator with a stimulus current of 3mA. R1 and R2 signals were obtained using the stimulus current of 1 to 3mA. Forty-two patients (3 males and 39 females) were included. Lobectomy was performed in 40 patients (95.2%) and total thyroidectomy in 2 (4.8%). Pathologic diagnoses were 30 papillary thyroid carcinomas, 2 follicular thyroid carcinomas, and 9 benign diseases. Conversion to open surgery occurred in 1 patient due to bleeding. Thus, 43 nerves at risk in 41 patients were analyzed. V1 and R1 signals were detected from all nerves. The mean V1 and R1 amplitudes were 738.7±391.4μV and 804.4±347.5μV, respectively, and 38 (88.3%) and 39 (90.7%) nerves had R1 and V1 amplitudes of more than 500μV. There were 2 cases (4.6%) of transient recurrent laryngeal nerve injury. R2 and V2 signals were detected in the 41 remaining nerves. The mean R2 and V2 amplitudes were 917.2±505.2μV and 715.7±356.2μV, respectively, and 36 (87.8%) and 32 (78.0%) nerves had respective R2 and V2 amplitudes of more than 500μV. Intraoperative neuromonitoring could be performed in a standardized manner in TOETVA, and the quality of intraoperative neuromonitoring was excellent. Further studies are needed to verify the feasibility of the current approach.

Characteristics of submental muscles function and hyoid bone movement in patients with dysphagia after stroke.

Dysphagia is one of the common complications after stroke. Dysphagia significantly increases the probability of serious adverse consequences. The purpose of this study was to compare the characteristics of submental muscles electromyography and hyoid motion parameters between patients with dysphagia after stroke and healthy controls, and whether there is a synergistic effect between the function of the submental muscles and the movement of the hyoid. Fifteen patients with post-stroke dysphagia and fifteen healthy adults simultaneously underwent the videofluoroscopic and surface electromyography of the submental muscles while swallowing 5ml of concentrated liquid barium sulphate. The electromyographic signal of the submental muscles was analysed along with parameters of hyoid movement. Stage transition duration and duration of surface electromyographic activity were extended significantly in post-stroke dysphagia patients(P<0.05). Surface electromyography amplitude and hyoid movement were significantly reduced in patients (P<0.05). There was a significant correlation between the maximum hyoid movement distance and the peak sEMG amplitude in healthy controls (r=0.660, P=0.014), but not in patients with dysphagia after stroke (r=0.425, P=0.148). Submental muscles electromyographic signal changes in patients may be the result of uncoordinated muscle contractions and decreased muscle strength. Furthermore, the reduced hyoid movement distance may be due to impaired function of the submental muscles. In addition, the submental muscles and hyoid movement or other swallowing structures functions were impaired to varying degrees, resulting in the disappearance of the correlation between the maximum movement distance of the hyoid and the peak amplitude.

Load-Specific Performance Fatigability, Coactivation, and Neuromuscular Responses to Fatiguing Forearm Flexion Muscle Actions in Women.

Benitez, B, Dinyer-McNeeley, TK, McCallum, L, Kwak, M, Succi, PJ, and Bergstrom, HC. Load-specific performance fatigability, coactivation, and neuromuscular responses to fatiguing forearm flexion muscle actions in women. J Strength Cond Res 37(4): 769-779, 2023-This study examined the effects of fatiguing, bilateral, dynamic constant external resistance (DCER) forearm flexion on performance fatigability, coactivation, and neuromuscular responses of the biceps brachii (BB) and triceps brachii (TB) at high (80% 1 repetition maximum [1RM]) and low (30% 1RM) relative loads in women. Ten women completed 1RM testing and repetitions to failure (RTF) at 30 and 80% 1RM. Maximal voluntary isometric force was measured before and after RTF. Electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) signals were measured from the BB and TB. Performance fatigability was greater (p < 0.05) after RTF at 30% (%∆ = 41.56 ± 18.61%) than 80% (%∆ = 19.65 ± 8.47%) 1RM. There was an increase in the coactivation ratio (less coactivation) between the initial and final repetitions at 30%, which may reflect greater increases in agonist muscle excitation (EMG AMP) relative to the antagonist for RTF at 30% than 80% 1RM. The initial repetitions EMG AMP was greater for 80% than 30% 1RM, but there was no difference between loads for the final repetitions. For both loads, there were increases in EMG MPF and MMG AMP and decreases in MMG MPF that may suggest fatigue-dependent recruitment of higher-threshold motor units. Thus, RTF at 30 and 80% 1RM during DCER forearm flexion may not necessitate additional muscle excitation to the antagonist muscle despite greater fatigability after RTF at 30% 1RM. These specific acute performance and neuromuscular responses may provide insight into the unique mechanism underlying adaptations to training performed at varying relative loads.

Centering prayer in the treatment of Parkinson's disease preliminary quality-of-life research

Parkinson's Disease (PD) affects nearly a million Americans, a number that will increase over the coming decades. L-DOPA has been the most effective treatment. While available medical therapies help control symptoms during the initial years following diagnosis, higher doses are required over time, increasing side effects and decreasing control of symptoms. As a result, patients suffering from PD become refractory to conventional treatments. The authors anecdotally observed a significant symptom reduction in a patient who practiced Centering Prayer (CP), taught by Hesse. As a last choice, the experience led the authors to apply teaching CP to four current patients to improve their quality of life. We studied these patients before and after practicing CP, assessing tremors by electromyography records and applying the Unified Parkinson's Disease Rating Scale (UPDRS). A control group of four PD patients with high UPDRS, who were not trained in CP, were also selected. During the active phase of PD symptoms, electromyography (EMG) testing was conducted before and 30 minutes after the CP session in the test group. EMG testing was also done on the control group during the active phase of symptoms, and the groups were compared for a reduction in EMG amplitude. All patients showed a significant reduction in EMG amplitude after the CP session. There were significant UPDRS score decrements at 30 and 45 minutes, lasting up to 60 minutes. These important clinical and EMG results were not found in the control group. With these results, our group plans to collect greater samples of PD patients for proposing CP practice as an alternative treatment for this Disease.

Two year follow-up and comparison of pelvic floor muscle electromyography after first vaginal delivery with and without episiotomy and its correlation with urinary incontinence: A prospective cohort study.

Few prospective studies have revealed the long-term neuromuscular alterations of pelvic floor after vaginal delivery. The aim of this study was to evaluate the impact of episiotomy on the electrical activity of pelvic floor muscle 2 years following vaginal delivery, and explore the relation between surface electromyography (sEMG) amplitudes and urinary incontinence. A total of 427 primiparous women with full-term singleton vaginal delivery were included in the cohort and 362 with no further births within the 2 year follow-up completed observations. Of these, 200 underwent episiotomy and 162 underwent nonepisiotomy. Clinical demographic characteristics, vaginal EMG variables and urinary incontinence-specific questionnaire scores were collected at 6 weeks, 6, 12 and 24 months after childbirth, respectively. Primary outcomes were the comparison of sEMG values between the episiotomy and nonepisiotomy groups throughout 2 years. Secondary outcomes were the correlation between sEMG of both groups and the incidence and severity of urinary incontinence. Spearman's correlation analysis, Kruskal-Wallis test and ANOVA with Bonferroni correction were used to analyze the variables. Amplitude of maximal fast and endurance contractions on sEMG in the episiotomy group was significantly lower than the nonepisiotomy counterpart. Such difference of sEMG persisted for a long period after birth: endurance contraction, 33.12 ± 8.92 vs 35.085 ± 9.98, p < 0.01 at 24 months, and fast contraction, 36.53 ± 8.87 vs 39.05 ± 9.98, p=0.01 at 12-month. Although there was no significant difference in incidence and severity of urinary incontinence between both groups, a negative correlation existed between EMG values of muscle contraction and urinary incontinence symptoms throughout. Primiparous women delivered with episiotomy demonstrated lower contractile sEMG activity of pelvic floor muscle in the long term. The lower sEMG values of fast contraction were associated with urinary incontinence symptoms.

Anticipatory postural adjustments in older versus young adults: a systematic review and meta-analysis

BackgroundAnticipatory postural adjustments (APAs) are a feedforward mechanism triggered in advance to a predictable perturbation, to help the individual counteract mechanical effects that the disturbance may cause. Whether or not this strategy is compromised in the elderly is not a consensus in the literature.MethodsIn this systematic review with meta-analysis, we investigated aging effects on postural control, based on anticipatory postural adjustments (APAs). We selected 11 eligible articles of the following databases: Lilacs, SciELO, PubMed, Cochrane Central, Embase, and CINAHL, involving 324 research participants, assessing their methodological quality and extracting electromyographic, posturographic, and kinematic measurements. We included studies that investigated the occurrence of APAs in healthy younger and older adults, published before 10th August 2022, in English. Studies involving participant with conditions that may affect balance or that did not report measures of onset or amplitude of electromyography (EMG), COP, or kinematics were excluded. To analyze the aggregated results from these studies, we performed the analysis based on the outcome measures (EMG, COP, or kinematic measures) used in individual studies. We calculated differences between younger and older adult groups as the mean differences between the groups and the estimated effect. Egger’s test was conducted to evaluate whether this meta-analysis had publication bias.ResultsThrough this review, older adults showed no significant difference in the velocity to perform a movement compared to the younger adults (MD 0.95, 95% CI −0.86, 2.76, I2 = 82%), but both muscle onset and center of pressure (COP) onset were significantly more delayed in older than in younger adults: erector spinae (MD −31.44, 95% CI −61.79, −1.09, I2 = 95%); rectus abdominis (RA) (MD −31.51, 95% CI −70.58, −3.57, I2 = 85%); tibialis anterior (TA) (MD −44.70, 95% CI −94.30, 4.91, I2 = 63%); soleus (SOL) (MD −37.74, 95% CI −65.43, −10.05, I2 = 91%); gastrocnemius (GAS) (MD −120.59, 95% CI −206.70, −34.49, I2 = 94%); quadriceps (Q) (MD −17.42, 95% CI −34.73, −0.12, I2 = 0%); biceps femoris (BF) (MD −117.47, 95% CI −192.55, −42.70, I2 = 97%); COP onset (MD −45.28, 95% CI −89.57, −0.98, I2 = 93%), and COP apa (COPapa) (MD 2.35, 95% CI −0.09, 4.79, I2 = 64%). These changes did not seem to be linked to the speed of movement but possibly to age-related physiological changes that indicated decreased motor control during APAs in older adults.ConclusionsOlder adults use different postural strategies that aim to increase the safety margin and stabilize the body to perform the movement, according to the requirements imposed, and this should be considered in rehabilitation protocols.Systematic review registrationPROSPERO CRD420119143198

Application of the Ratings of Perceived Exertion-Clamp Model to Examine the Effects of Joint Angle on the Time Course of Torque and Neuromuscular Responses During a Sustained, Isometric Forearm Flexion to Task Failure.

Abstract Smith, RW, Housh, TJ, Anders, JPV, Neltner, TJ, Arnett, JE, Schmidt, RJ, and Johnson, GO. Application of the ratings of perceived exertion-clamp model to examine the effects of joint angle on the time course of torque and neuromuscular responses during a sustained, isometric forearm flexion to task failure. J Strength Cond Res 37(5): 1023–1033, 2023—The present study used the ratings of perceived exertion (RPE)-clamp model during a sustained, isometric forearm flexion task to failure to determine the effects of joint angle on torque and neuromuscular responses. Twelve college-aged women performed two 3-second maximal voluntary isometric contractions at elbow joint angles (EJ) of 75°, 100°, and 125° before sustained, isometric, forearm flexions anchored to RPE = 7 to task failure (defined as RPE &gt; 7, or the torque was reduced to zero) at EJ75, EJ100, and EJ125. The amplitude (AMP) and frequency (MPF) of the electromyographic (EMG) and mechanomyographic (MMG) signals from the biceps brachii were recorded. Repeated-measures ANOVAs and post hoc comparisons were used to examine differences across time and between joint angles for torque and neuromuscular parameters. A p-value ≤0.05 was considered significant. For each joint angle, there was a decrease (p &lt; 0.05) in torque across the sustained, isometric task. Collapsed across joint angle, there were decreases (p &lt; 0.001, = 0.378) in EMG AMP from 30 to 100% time to task failure. No changes were observed, however, for the other neuromuscular responses. The subjects voluntarily reduced torque to maintain RPE = 7 for each joint angle, and we hypothesize that RPE was maintained by afferent feedback from group III/IV motor neurons and corollary discharge (efferent copy of an internal signal that develops from central motor commands). The RPE-Clamp Model may be extended to athletes recovering from injury because a self-selected exercise intensity may be perceived as more enjoyable and promote adherence.

Inspiratory muscle reflex control after incomplete cervical spinal cord injury.

In healthy individuals, loading inspiratory muscles by brief inspiratory occlusion produces a short-latency inhibitory reflex (IR) in the electromyographic (EMG) activity of scalene and diaphragm muscles. This IR may play a protective role to prevent aspiration and airway collapse during sleep. In people with motor and sensory complete cervical spinal cord injury (cSCI), who were able to breathe independently, this IR was predominantly absent. Here, we investigated the reflex response to brief airway occlusion in 16 participants with sensory incomplete cSCI [American spinal injury association impairment scale (AIS) score B or C]. Surface EMG was recorded from scalene muscles and the lateral chest wall (overlying diaphragm). The airway occlusion evoked a small change in mouth pressure resembling a physiological occlusion. The short-latency IR was present in 10 (63%) sensory incomplete cSCI participants; significantly higher than the IR incidence observed in complete cSCI participants in our previous study (14%; P = 0.003). When present, mean IR latency across all muscles was 58 ms (range 29-79 ms), and mean rectified EMG amplitude decreased to 37% preocclusion levels. Participants without an IR had untreated severe obstructive sleep apnea (OSA), in contrast to those with an IR, who had either had no, mild, or treated OSA (P = 0.002). Insufficient power did not allow statistical comparison between IR presence or absence and participant clinical characteristics. In conclusion, spared sensory connections or intersegmental connections may be necessary to generate the IR. Future studies to establish whether IR presence is related to respiratory morbidity in the tetraplegic population are required.NEW & NOTEWORTHY Individuals with incomplete cSCI were tested for the presence of a short latency reflex inhibition of inspiratory muscles, by brief airway occlusion. The reflex was 4.5 times more prevalent in this group compared with those with complete cSCI and is similar to the incidence in able-bodied people. Participants without this reflex all had untreated severe OSA, in contrast to those with an IR, who either had no, mild, or treated OSA. This work reveals novel differences in the reflex control of inspiratory muscles across the cSCI population.

O054 Genioglossus neural drive and upper airway dilation in people with obstructive sleep apnoea during wakefulness

Abstract Introduction Genioglossus neural drive and the ensuing tongue dilatory movement may be dissociated in obstructive sleep apnoea (OSA), but this has not been studied. This study aimed to investigate this relationship and its potential role in OSA pathophysiology. Methods During awake nasal breathing in the supine position, inspiratory tongue dilatory movement, quantified with tagged magnetic resonance imaging, and inspiratory peak genioglossus electromyography (EMG) normalised to the maximum voluntary contraction (tongue protrusion), were measured in 4 tongue neuromuscular compartments from 8 controls [apnea-hypopnea index (AHI)&amp;lt;5 events/h] and 34 patients with untreated OSA [AHI&amp;gt;10 events/h]. Results Although larger inspiratory dilatory movement was associated with increased drive to genioglossus (partial Spearman, r=0.23, p=0.016, n=115/68% of compartments), in 14% of the compartments (n=16), there was a large dilatory (&amp;gt;1mm) movement but minimal EMG (&amp;lt;4th percentile). This occurred only in the horizontal compartment. In another group of 18 compartments (16%), there was a large peak EMG (&amp;gt;4th percentile) but minimal dilatory movement (&amp;lt;1mm). This occurred more commonly in the oblique compartments. Dissociation between the amplitude of the peak EMG and inspiratory tongue dilatory movement was most commonly seen in severe OSA patients (AHI&amp;gt;30 events/h, Fisher's exact test, p=0.047). Conclusions Inspiratory tongue dilatory function generally remains closely linked to muscle drive during wakefulness, with larger movement associated with higher peak EMG. However, for approximately one-third of the neuromuscular tongue compartments, neural drive was dissociated from the dilatory motion in severe OSA patients. This may contribute to OSA pathogenesis and have implications for neural stimulation therapy targets.

Variability in Normalization Methods of Surface Electromyography Signals in Eccentric Hamstring Contraction

In human movement analysis, normalization of a surface electromyography signal is a crucial step; therefore, parameter selection for this procedure must be adequately justified. The aim of this research was to determine the variability of electromyography signals in eccentric hamstring contraction under different normalization parameters. Cross-sectional study. Nine university rugby players (age 21.50 [3.61]y; body mass index 21.50 [4.95]) and no history of recent hamstring injury. Values from maximum voluntary isometric contraction protocol and task related (ie,Nordic hamstring exercise) were used for surface electromyography signal normalization. Intersubject and intrasubject variation coefficients were used for normalization method variability and for signal reproducibility, respectively. Intrasubject variation coefficient value indicates acceptable reproducibility of surface electromyography (less than 12%) for all normalization procedures. Lower values of intersubject variation coefficient value were achieved for normalization procedures using task-related values. Parameters extracted from task execution provided less variability for surface electromyography amplitude normalization in eccentric hamstring muscle contractions.

Coactivation does not contribute to fatigue-induced decreases in torque during reciprocal, isokinetic muscle actions

BACKGROUND: Studies of coactivation have typically utilized single movement isometric or isokinetic fatiguing muscle actions. OBJECTIVE: The purpose of the current study was to examine coactivation of the biceps brachii (BB) and triceps brachii (TB) in response to a maximal, reciprocal, isokinetic fatiguing task of the forearm flexors and extensors at slow (60∘/s) and moderate (180∘/s) isokinetic velocities in men. METHODS: Ten men (mean ± SD: age = 21.6 ± 1.3 years) completed 50 consecutive, maximal, reciprocal, isokinetic muscle actions of the right forearm flexors and extensors at 60 and 180∘/s. The amplitude (AMP) and mean power frequency (MPF) contents of the electromyographic (EMG) and mechanomyographic (MMG) signals from the BB and TB were recorded simultaneously throughout the fatiguing task. Repeated measures ANOVAs with Tukey post hocs were used to determine mean differences for the torque and neuromuscular parameters across repetitions. RESULTS: The torque analyses indicated greater fatigability at 180∘/s, compared to 60∘/s (p= 0.02). There were no significant changes in EMG AMP for either muscle during flexion or extension at 60∘/s (p&gt; 0.05). At 180∘/s, there were significant increases in agonist EMG AMP (p= 0.01 to 0.004), however, no changes in antagonist EMG AMP (p&gt; 0.05). For EMG MPF, there were significant decreases during flexion and extension (p&lt; 0.001 to p= 0.02) at both velocities, collapsed across muscle. There were no significant (p&gt; 0.05) changes across repetition for MMG AMP or MPF. CONCLUSIONS: This study indicated velocity-specific responses to fatigue, with a greater magnitude of fatigability at 180∘/s. Furthermore, despite increases in EMG AMP of the agonist muscles at 180∘/s only, it was not sufficient to alter the ratio of coactivation, likely due to common neural drive between muscles. Thus, the decreases in torque in the present study were not attributable to increases in coactivation.

Study on diagnosis and treatment of lumbar disc herniation and related factors based on dynamic electromyography

To analyze dynamic electromyography characteristics and related factors of lumbar back muscle activity in patients with lumbar disc herniation, and to clarify the clinical significance of dynamic electromyography in the diagnosis and treatment of patients with lumbar disc herniation(LDH). From September 2014 to March 2021, 40 patients with lumbar disc herniation(LDH group) were detected by surface electromyography telemeter. There were 14 males and 26 females, aged from 20 to 61 years old, with an average of(40.68±10.56) years old, the course of illness was from 1 to 120 months, with an average of (17.75±27.56) months. In addition, 12 normal people were recruited as the control group. There were 2 males and 10 females. The age ranged from 24 to 53 years old, with an average of(36.50±10.30) years old. All subjects were subjected to dynamic electromyographic tests of the subthoracic erector spinae, lumbar erector spinae, and multifidus muscles during static standing and trunk flexion and extension. Compare the EMG activity data (average EMG amplitude, median frequency, original EMG graph) of the tested muscles between patients with lumbar disc herniation and normal people, and analyze the correlation between the general data of patients with lumbar disc herniation and the tested muscle EMG data. When standing still, the average electromyographic amplitude of the erector spinal muscle of the right and left thoracic segments of the subjects in the LDH group increased compared with the control group, and the difference was significant(P<0.05). In the trunk flexion and extension, the average electromyographic amplitude of the right and left proximal thoracic erector spinae, the right left lumbar erector spinae, and the right left multifidus muscle of the subjects in the LDH group are all larger than the control group, and the difference was significant(P<0.05). In the trunk flexion and extension, the median frequencies of the right left proximal thoracic erector spinae、the right left lumbar erector spinae, and the right left multifidus muscle of the subjects in the LDH group were all larger than the normal control group, and the difference was significant (P<0.05). During trunk flexion and extension, the original electromyographic patterns of subjects in the LDH group were significantly different from those in the control group. During the maintenance of the maximum trunk flexion of the subjects in the LDH group, there was a high level of electromyographic activity of the lower back muscles, and the electromyographic static signals that should appear regularly in the original signal could not be distinguished. When the trunk was flexed and extended, had gender, age, weight and height of subjects in the LDH group were not significantly correlated with the average EMG amplitude and median frequency of bilateral proximal thoracic, lumbar erector spinae and bilateral multifidus muscles respectively(P>0.05). Patients with lumbar disc herniation have characteristic surface EMG changes in the back muscles that are different from those of normal people. These features can more objectively reflect the patient's muscle condition and can be an effective indicator for the diagnosis and treatment effect evaluation of patients with lumbar disc herniation. It can be seen that surface electromyography is not only a detection method, it can be considered in the routine diagnosis and treatment plan of LDH to guide clinical work.

Sex-specific myoelectric manifestations of localized fatigue during a multi-joint repetitive task

We have previously demonstrated that fatigue at different locations impacts joint angles, angular variability, and coordination variability differently. However, the neuromuscular control aspects underlying these kinematic changes have never been demonstrated. Seventeen young adults (8 males) were recruited. Electromyographic electrodes were placed on: upper trapezius, pectoralis major, anterior and middle deltoid, biceps and triceps brachii, and left and right erector spinae. Subjects performed the repetitive pointing task (RPT) at 1 Hz for 30 s before and after localized fatigue tasks, which consisted of one shoulder, one elbow and one lower back isometric fatiguing protocols until exhaustion in randomized order. Electromyographic amplitude (RMS), variability (SD) and mean power frequency (MnPF) were calculated for each of the pre-fatigue and post-fatigue RPT trials. There were sex × fatigue location interaction effects on upper trapezius RMS (p = 0.038) with males’ values increasing the most after shoulder fatigue. Females’ triceps brachii RMS was greater compared to males after shoulder, elbow, and trunk fatigue (p = 0.003, p = 0.001 and p = 0.007 respectively). There were sex × fatigue location effects on left erector spinae MnPF (p = 0.011) with males and females’ values decreasing the most after trunk fatigue, but more so in males. Results demonstrate that males and females compensate differently during a repetitive pointing task when their elbows, shoulders and trunks are locally fatigued, which could have implications on sex-specific workplace injury risks. See Table 1 for acronyms.

Administration of neostigmine after tracheal intubation shortens time to successful intraoperative neuromonitoring during thyroid surgery: a randomized controlled trial

This prospective, randomized controlled trial evaluated the effect of neostigmine for intraoperative neuromonitoring (IONM) during thyroid surgery. Forty subjects undergoing thyroidectomy with IONM, randomized into neostigmine administration after tracheal intubation (Group N, n = 20) or control treatment with normal saline (Group C, n = 20), completed the trial. Electromyography amplitudes of the vagus nerve (V1) were recorded before thyroid dissection. The time from the initial V1 signal check to successful V1 stimulation was recorded. In Group N, all the patients had a successful V1 signal at the first check, whereas ten (50%) patients in Group C had a time delay between the initial V1 check and successful V1 (p < 0.001). The mean delay time among the delayed patients in Group C was 11.2 ± 1.4 min. The mean time from skin incision to successful V1 stimulation was significantly shorter in Group N than in Group C (15.4 ± 2.4 min vs. 19.9 ± 5.7 min, p = 0.003). In Groups N and C, the mean V1 amplitudes were 962.2 ± 434.5 μV vs. 802.3 ± 382.7 μV (p = 0.225), respectively, and the mean R1 amplitudes were 1240.0 ± 836.5 μV vs. 1023.4 ± 455.8 μV (p = 0.316), respectively. There was one bucking event in Group N. In conclusion, neostigmine administration immediately after tracheal intubation can be useful to reverse neuromuscular blockade for successful IONM in thyroid surgeries.

Anatomy and clinical application of suprascapular nerve to accessory nerve transfer.

BACKGROUNDLoss of motor function in the trapezius muscle is one complication of radical neck dissection after cutting the accessory nerve (AN) during surgery. Nerve repair is an effective method to restore trapezius muscle function, and includes neurolysis, direct suture, and nerve grafting. The suprascapular nerve (SCN) and AN are next to each other in position. The function of the AN and SCN in shoulder elevation and abduction movement is synergistic. SCN might be considered by surgeons for AN reanimation.AIMTo obtain anatomical and clinical data for partial suprascapular nerve-to-AN transfer.METHODSTen sides of cadavers perfused with formalin were obtained from the Department of Human Anatomy, Histology and Embryology, Peking University Health Science Center. The SCN (n = 10) and AN (n = 10) were carefully dissected in the posterior triangle of the neck, and the trapezius muscle was dissected to fully display the accessory nerve. The length of the SCN from the origin of the brachial plexus (a point) to the scapular notch (b point) and the distance of the SCN from the origin point (a point) to the point (c point) where the AN entered the border of the trapezius muscle were measured. The length and branches of the AN in the trapezius muscle were measured. A female patient aged 55 years underwent surgery for partial SCN to AN transfer at Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology. The patient suffered from recurrent upper gingival cancer. Radical neck dissection was performed on the right side, and the right AN was removed at the intersection between the nerve and the posterior border of the SCM muscle. One-third of the diameter of the SCN was cut off, and combined epineurial and perineurial sutures were applied between the distal end of the cut-off fascicles of the SCN and the proximal end of the AN without tension. Both subjective and objective evaluations were performed before, three months after, and nine months after surgery. For the subjective evaluation, the questionnaire included the Neck Dissection Impairment Index (NDII) and the Constant Shoulder Scale. Electromyography was used for the objective examination. Data were analyzed using t tests with SPSS 19.0 software to determine the relationship between the length of the SCN and the linear distance. A P value of < 0.05 was considered as statistically significant.RESULTSThe whole length of the AN in the trapezius muscle was 16.89 cm. The average numbers of branches distributed in the descending, horizontal and ascending portions were 3.8, 2.6 and 2.2, respectively. The diameter of the AN was 1.94 mm at the anterior border of the trapezius. The length of the suprascapular nerve from the origin of the brachial plexus to the scapular notch was longer than the distance of the suprascapular nerve from the origin point to the point where the accessory nerve entered the upper edge of the trapezius muscle. The amplitude of trapezius muscle electromyography indicated that both the horizontal and ascending portions of the trapezius muscle on the right side had better function than the left side nine months after surgery. The results showed that the right-sided supraspinatus and infraspinatus muscles did not lose more function than the left side.CONCLUSIONBased on anatomical data and clinical application, partial suprascapular nerve-to-AN transfer could be achieved and may improve innervation of the affected trapezius muscle after radical neck dissection.

No effect of coactivation on fatigue-induced decreases in isokinetic and isometric torque in healthy young male adults

BackgroundAntagonist activation may contribute to fatigue-induced decreases in torque while assisting in the maintenance of joint stability. This study utilized a reciprocal, slow velocity (60°·s−1) forearm flexion and extension fatiguing task to examine the contributions of coactivation to torque production at slow and moderate (180°·s−1) velocities, as well as during a maximal voluntary isometric contraction (MVIC). MethodsTwelve recreationally active men (mean ± SD: age = 21.7 ± 1.6 years; body mass = 83.5 ± 8.8 kg; height = 179.4 ± 5.2 cm) completed isokinetic (60 and 180°·s−1) and isometric pre-testing of forearm flexion and extension, followed by 50 maximal, reciprocal, isokinetic muscle actions at 60°·s−1, followed by post-testing. The amplitude (AMP) of the electromyographic (EMG) signals from the biceps and triceps brachii were simultaneously recorded. Torque and EMG AMP were normalized to the corresponding values from the pre-testing peak torque movements. Repeated measures ANOVAs and pairwise comparisons were used to identify mean changes in torque, EMG AMP, and coactivation ratios. ResultsThe torque analyses indicated greater (p < 0.03) decreases for 180°·s−1 (24%) and MVIC (23%) than 60°·s−1 (14%) for forearm flexion. For forearm extension, there were no differences (p > 0.05) in fatigability between velocities. For EMG AMP there were no changes (p > 0.05) from pre- to post-testing for any velocity or movement. There were no changes (p > 0.05) in the coactivation ratio for forearm flexion, but significant increases (13.6 ± 6.6 to 16.9 ± 6.0; p = 0.003) for forearm extension, collapsed across Velocity. ConclusionsThere was velocity- and movement-specific fatigability for forearm flexion and extension. The parallel, fatigue-induced EMG AMP responses indicated that coactivation did not contribute to the decreases in torque and would not affect elbow joint stability.

Differences in causes of stiff knee gait in knee extensor activity or ankle kinematics: A cross-sectional study

BackgroundStiff knee gait (SKG), a common occurrence after the onset of stroke, is caused by hyperactivity of the rectus femoris during the swing phase. Another cause of SKG is the weakness of push-off in hemiparetic gait. Prior research did not consider the effect of the magnitude of knee extensors in their subjects. Research questionDoes the cause of SKG differ between patients with high and low knee extensor activities during the swing phase? MethodsWe examined 38 patients with chronic stroke hemiplegia who presented with SKG. After placing an inertia sensor and an electromyogram, patients walked 10 m at a comfortable speed. All patients were categorized per the sign of the principal component 2 (PC2) as a component with large factor loadings of knee extensors attained from the electromyographic amplitude during the early swing phase of the paretic limb. Then, the kinematic parameters of knee flexion and other gait parameters in each group were compared, and a correlation analysis was performed. ResultsIn the high PC2 group, the timing of peak knee flexion during the swing phase was early, and vastus lateralis activity during the preswing phase negatively correlated with the knee-flexion angle during the swing phase. In the low PC2 group, the angular velocity of ankle plantar flexion at the toe-off was slow, which positively correlated with the knee-flexion angle during the swing phase. SignificanceThe cause of SKG could be an inappropriate activity of the vastus lateralis rather than the rectus femoris in patients with high knee extensor activity and slow plantar-flexion velocity at toe-off in patients with low knee extensor activity. Not all causes of SKG in patients with hemiplegia are common, and different treatment strategies are needed per the individuality of spastic knee extensor activity.

Robust estimation of lumbar joint forces in symmetric and asymmetric lifting tasks via large-scale electromyography-driven musculoskeletal models

Low back joint compression forces have been linked to the development of chronic back pain. Back-support exoskeletons controllers based on low back compression force estimates could potentially reduce the incidence of chronic pain. However, progress has been hampered by the lack of robust and accurate methods for compression force estimation. Electromyography (EMG)-driven musculoskeletal models have been proposed to estimate lumbar compression forces. Nonetheless, they commonly underrepresented trunk musculoskeletal geometries or activation–contraction dynamics, preventing validation across large sets of conditions. Here, we develop and validate a subject-specific large-scale (238 muscle–tendon units) EMG-driven musculoskeletal model for the estimation of lumbosacral moments and compression forces, under eight box-lifting conditions. Ten participants performed symmetric and asymmetric box liftings under 5 and 15 kg weight conditions. EMG-driven model-based estimates of L5/S1 flexion–extension moments displayed high correlation, R2 (mean range: 0.88–0.94), and root mean squared errors between 0.21 and 0.38 Nm/kg, with respect to reference inverse dynamics moments. Model-derived muscle forces were utilized to compute lumbosacral compression forces, which reached eight times participants body weight in 15 kg liftings. For conditions involving stooped postures, model-based analyses revealed a predominant decrease in peak lumbar EMG amplitude during the lowering phase of liftings, which did not translate into a decrease in muscle–tendon forces. During eccentric contraction (box-lowering), our model employed the muscle force–velocity relationship to preserve muscle force despite significant EMG reduction. Our modeling methodology can inherently account for EMG-to-force non-linearities across subjects and lifting conditions, a crucial requirement for robust real-time control of back-support exoskeletons.

The facilitation of trunk muscles by abdominal bracing during walking in chronic low back pain patients

Walking is known to be beneficial for chronic low back pain (LBP) patients and fast walking recruits more trunk muscles. Abdominal bracing has also been shown to improve LBP and facilitate several trunk muscles. We aimed to investigate the effects of walking velocity and abdominal bracing on the activation of trunk muscles in chronic LBP patients during walking. Forty-six volunteers with chronic LBP underwent walking exercise on the treadmill without (“non-braced walking”) and with abdominal bracing (“braced walking”) at speeds of 4, 5, and 6 km/h, with the surface electrodes placed on their trunk muscles to measure muscle activity. The root mean square values of the surface electromyography amplitude data were obtained at the multifidus of lower (ML) and upper lumbar (MU), erector spinae of lower lumbar (EL) and thoracic (ET), rectus abdominis (RA), and external oblique (EO). All muscles activated significantly more at faster walking. The “braced walking” facilitated the ET and RA significantly more than the “non-braced walking”. The interaction between the walking speed and abdominal bracing was significant at ML, MU, and RA. The increase in muscle activation observed at lower speed diminished as speed increased. Since “braced walking” seems to additionally facilitate the trunk muscles especially at slower gait speeds, patients who cannot walk fast may still be able to train their muscles by “braced walking.”