Fine-wire EMG Research Articles

Hypercapnia elicits changes in diaphragm neuromotor control and respiratory timing parameters in awake rats

The diaphragm muscle (DIAm) is the primary inspiratory muscle in mammals. At baseline, expiration is passive; however, with increased CO2 expiration becomes active, involving the inhibition of postinspiratory DIAm activity. The neuromotor control of the DIAm involves both the recruitment and frequency coding of DIAm motor units (MU’s) and it is not clear which aspect plays a greater role with exposure to hypercapnia. The activity of DIAm MU’s can be split into three phases: recruitment, sustained activity, and derecruitment. The goal of the present study was to evaluate the effects of hypercapnia on the neuromotor control of the DIAm in awake Sprague-Dawley rats. We hypothesized that hypercapnia would lead to increased respiratory drive as estimated by the root-mean-square (RMS) EMG amplitude at the end of the recruitment phase. Accordingly, we implanted chronic fine-wire EMG electrodes into the mid-costal region of the right side of the DIAm in 10 (5 female, 5 male) anesthetized rats. Three days after recovery from surgery, we recorded DIAm EMG in lightly restrained awake rats during normocapnia and hypercapnia (7% CO2, 21% O2, balance N2). We estimated the duration of motor unit recruitment, sustained activity, and derecruitment by assessing the stationarity of DIAm EMG activity and used these durations to determine the RMS EMG amplitude at the completion of recruitment, at the peak, and immediately prior to derecruitment (normalized to the average peak RMS EMG amplitude during normocapnia within each animal). We found that the RMS EMG amplitude at the completion of recruitment was increased from ~75% to 85% with hypercapnia. Peak RMS EMG amplitude during hypercapnia increased from 100% to ~120%, while the amplitude at the onset of derecruitment increased from ~50% to 95%. These data suggest that ~70% of the total RMS EMG peak amplitude can be attributed primarily to motor unit recruitment, while the remaining ~30% can be attributed to frequency modulation during hypercapnia. Importantly the onset-to-offset amplitude difference was ~25% during normocapnia and ~15% during hypercapnia, suggesting that DIAm MU’s were derecruited at higher discharge rates with hypercapnia, likely due to inhibition. We also found that compared to normocapnia, respiratory rate increased from ~85 breaths/min to 125 breaths/min while the burst duration decreased from ~600 ms to ~400 ms during hypercapnia. The duty cycle was maintained around 80% for both, however the duty cycle of the sustained activity duration (i.e. the period during which MU’s are remaining activated) decreased from ~56% to ~28%. Taken together, our data suggest that hypercapnia in awake rats results in an increase in the number of motor units recruited and their discharge rates as well as changes in the phases of DIAm MU activity indicative of active expiration. Funded by NIH HL-146114. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Intermuscular Coherence Of Rotator Cuff And Deltoid Muscles Varies With Force Output

PURPOSE:To identify intermuscular EMG coherence patterns between the rotator cuff and deltoid muscles at different force levels. METHODS:Surface EMG electrodes were used to record activity from the anterior deltoid (AD), middle deltoid (MD), and infraspinatus (IS) muscles of the dominant shoulder in 7 healthy individuals (mean age ± SD = 19 ± 1, 6 females, 1 male). An intramuscular fine-wire EMG electrode was inserted into supraspinatus (SS). Participants performed 30s contractions of isometric shoulder abduction in the scapular plane at 30° at 25% (low-load), 50% (medium-load) and 75% (high-load) of maximum voluntary contraction with visual feedback of the force output. EMG amplitudes and coherence of each muscle pair in the common drive (0-5 Hz), physiological force tremor (5-12 Hz), beta (15-35 Hz), low-gamma (35-60 Hz) and high-gamma (60-100 Hz) bands were compared across the 3 force levels. RESULTS:EMG amplitudes of all muscles increased as force level increased (all p < 0.05). EMG coherence between IS and deltoid muscles increased as force level increased in the low-gamma band (p < 0.05). SS-IS coherence was also the highest during high-load task in the low-gamma band. These data indicate that additional neural drive with higher force levels stemming from subcortical origin likely mediate the increase in coherence between these muscles. However, SS-IS coherence during the medium and high load tasks were lower than that during the low-load task in the common drive band (p < 0.05), indicating that the increase in drive to these muscles for increasing force output is not targeted at common last-order neurons. Similarly, SS-AD coherence during the high-load task was lower than that during the medium-load task in the beta band (p < 0.05) and SS-AD and SS-MD was lower in the tremor band (p < 0.05) at higher force loads. The reduction in coherence between the SS and deltoid muscles and the SS and IS may serve to protect the humeral head from migrating superiorly at higher force loads. CONCLUSIONS:Increasing force output led to decreased coherence within the rotator cuff muscles and between supraspinatus and the deltoid muscles, but increased coherence between infraspinatus and the deltoid muscles. This likely serves as a protective mechanism against superior humeral head migration.

Electromyographic Evaluation of Early-Stage Shoulder Rehabilitation Exercises Following Rotator Cuff Repair.

BackgroundElectromyography (EMG) is frequently used as a guide for exercise rehabilitation progression following rotator cuff repair. Knowledge of EMG activity during passive and active-assisted exercises may help guide clinicians when considering exercise prescription in the early post-operative period.PurposeThe purpose of this study was to investigate EMG activity of the rotator cuff and deltoid musculature during passive and active-assisted shoulder range of motion (ROM) exercises commonly performed in post-operative rehabilitation.Study DesignDescriptive cohort laboratory study using healthy subjects.MethodsIn sixteen active healthy volunteers, surface and fine-wire EMG activity was measured in the supraspinatus, infraspinatus, subscapularis, and anterior, middle and posterior deltoid muscles during eight common ROM exercises. Mean %MVIC values and 95% confidence intervals were used to rank exercises from the least to the most amount of muscular activity generated during the exercises.ResultsStandard pendulum exercises generated low levels of EMG activity in the supraspinatus and infraspinatus (≤15% MVIC), while active-assisted table slides, and the upright wall slide generated low levels of EMG activity in only the supraspinatus. No exercises were found to generate low levels of muscular activation (≤15% MVIC) in the subscapularis.ConclusionThis study found no clear distinctions between the EMG activity of the supraspinatus or the infraspinatus occurring during common passive and active-assisted ROM exercises. Subdividing ROM exercises based on muscle activity, may not be necessary to guide progression of exercises prior to commencing active motion after rotator cuff repair.Level of EvidenceLevel 3b

Verification of intramuscular electromyography electrode placement for neuromuscular partitions of infraspinatus

The infraspinatus muscle is composed of three neuromuscular partitions: superior, middle and inferior. Although methods for fine-wire EMG electrode insertion into these partitions have been developed and used, it has yet to be verified. The purpose of this cadaveric EMG needle placement study was to assess the accuracy and reproducibility of a protocol used to target the three partitions of infraspinatus. On seven shoulder specimens, two investigators inserted needles into each superior, middle and inferior partition according to a previously developed protocol. Each was blinded to the other’s insertion sites. The specimens were dissected and the location of each needle was digitized and modeled in 3D. Of the 42 needles that were inserted, 32 were placed in the targeted partition. The highest accuracy rate occurred for the middle partition (100%), followed by the inferior (71.4%) and then the superior (57.1%). When the needles were not placed in the targeted partition, they were located in the neighboring partition within infraspinatus or the teres minor muscle. The current study showed the middle partition could be targeted accurately, whereas the superior and inferior partitions were more challenging. Ultrasound guidance may be necessary to ensure accurate placement into all parts of infraspinatus.

Postural cueing increases multifidus activation during stabilization exercise in participants with chronic and recurrent low back pain: An electromyographic study

Persons with low back pain (LBP) have demonstrated altered morphology and function of the deep multifidus (DM). This study examined the effects of postural cueing for increased lumbar lordosis on DM and longissimus thoracis (LT) activation during lumbar stabilization exercises (LSE) performed by persons with LBP. Nine adults with a history of chronic or recurrent LBP were recruited. Fine-wire EMG data was collected while participants performed 10 LSE’s in neutral posture and with postural cueing. Percent maximum voluntary isometric contraction of L5 DM and T12 LT, and ratios of activation (DM/LT) were analyzed. There was a significant main effect for posture on DM activation (p < 0.001), indicating greater activation levels during exercises performed with postural cueing vs. neutral posture. LT activation did not increase significantly with postural cueing. Following a significant 1-way repeated measures ANOVA (p = 0.034) for the postural cueing condition, pairwise comparisons demonstrated significantly higher DM/LT activation ratios for prone leg lift, variable-angle Roman chair at 15°, bridging, and bilateral arm and leg lift. These results suggest postural cueing can be used across a range of LSE intensities to increase DM activation without a significant increase in LT activation in patients with chronic or recurrent LBP.

Aminophylline increases parasternal muscle action in awake canines

The traditional theophylline bronchodilator, aminophylline, is still widely used, especially in the treatment of COPD. The effects of aminophylline on ventilation and action of the costal diaphragm have been previously defined, but other respiratory muscles – notably the chest wall, are not well determined. Therefore, we investigated the effects of aminophylline on the Parasternal intercostal, a key obligatory inspiratory muscle, examining muscle length, shortening and EMG. We studied 11 awake canines, chronically implanted with sonomicrometer crystals and fine-wire EMG electrodes in the parasternal muscle. Ventilatory parameters, muscle length (shortening), and moving average muscle EMG activity, were measured at baseline and with aminophylline, during resting and hypercapnic stimulated breathing. Experiments were carried out prior to administration of aminophylline (baseline), and 1.5 h after loading and ongoing infusion. Minute ventilation, tidal volume and respiratory frequency all increased significantly with aminophylline, both during resting breathing and at equivalent levels of hypercapnic stimulated breathing. Parasternal baseline muscle length was entirely unchanged with aminophylline. Parasternal shortening increased significantly with aminophylline while corresponding parasternal EMG activity remained constant, consistent with increased contractility. Thus, in awake, intact mammals, aminophylline, in the usual therapeutic range, elicits increased ventilation and increased contractility of all primary inspiratory respiratory muscles, including both chest wall and diaphragm.

Three-dimensional amplitude characteristics of masseter motor units and representativeness of extracted motor unit samples

ObjectiveThis study aimed to characterize amplitude topographies for masseter motor units (MUs) three-dimensionally, and to assess whether high-density surface electromyography (HDsEMG) is able to detect MU samples that represent the masseter’s entire MU pool. MethodsTen healthy adult volunteers participated in the study, which combined three EMG techniques. A HDsEMG grid covering the entire masseter, and intramuscular fine-wire electrodes were used to obtain two independent MU samples for comparison. The MUs’ amplitude profiles in the dimension of muscle depth were determined using scanning EMG. All data were recorded simultaneously during a low, constant contraction level controlled by 3D force feedback. ResultsThe median medio-lateral diameter of 4.4 mm (range: 1.2–7.9 mm) for MUs detected by HDsEMG did not differ significantly (Mann-Whitney-U test, p = 0.805) from that of 3.9 mm (0.6–8.6 mm) for MUs detected by fine-wire EMG. For individual subjects, the medio-lateral diameters of all HDsEMG-detected MUs spanned 70.5% (19.2–75.1%) of the masseter’s thickness. ConclusionsHDsEMG is able to examine small and large MUs from a great masseter proportion in one single measurement. SignificanceClinical application of HDsEMG might contribute to a better understanding of neuromuscular adaptations in patients with temporomandibular disorders (TMD) and could allow for monitoring treatment effects.

Representing fine-wire EMG with surface EMG in three thigh muscles during high knee flexion movements

Activation waveforms of vastus intermedius, adductor magnus, and semimembranosus have not been reported for high knee flexion activities such as kneeling or squatting, likely due to the invasive procedures required for their measurement. Their relatively large physiological cross sectional areas would suggest their contributions to knee joint loading could be considerable. Therefore, the purpose of this study was to quantify the activities of these muscles using fine-wire EMG and to assess easy to measure surface sites (vastus lateralis, rectus femoris, vastus medialis, semitendinosus, and biceps femoris) for their potential as proxy measures using <10 %MVC RMS and >0.85 R2 as criteria for successful representation of deep muscle activity by that measured at a surface site. Overall, no surface and fine-wire site pair met both criteria for these movements. When fine-wire measurement of muscle activity is infeasible or impractical, the waveforms presented in supplementary material could be used as a guide for the activity of these deep muscles. Although select muscles for some participants satisfied our criteria, inter-participant variability was considerable. Therefore, future muscle models may benefit from fine-wire measurement of these muscles, but researchers should be cautious of electrode site specificity.

Adductor magnus: An EMG investigation into proximal and distal portions and direction specific action

Cadaveric studies indicate that adductor magnus is structurally partitioned into at least two regions. The aim of this study was to investigate the direction-specific actions of proximal and distal portions of adductor magnus, and in doing so determine if these segments have distinct functional roles. Fine-wire EMG electrodes were inserted into two portions of adductor magnus of 12 healthy young adults. Muscle activity was recorded during maximum voluntary isometric contractions (MVICs) across eight tests (hip flexion/extension, internal/external rotation, abduction, and adduction at 0°, 45°, and 90° hip flexion). Median activity within each action (normalized to peak) was compared between segments using repeated measures nonparametric tests (α = 0.05). An effect size (ES = z-score/√sample size) was calculated to determine the magnitude of difference between muscle segments. The relative contribution of each muscle segment differed significantly during internal rotation (P < 0.001; ES = 0.88) and external rotation (P = 0.003, ES = 0.79). The distal portion was most active during extension [median (interquartile range); 100(0)% MVIC)] and internal rotation [58(34)% MVIC]. The proximal portion was most active during extension [100(49)% MVIC] and adduction [59(64)%MVIC], with low level activity during external rotation [15(41)%MVIC]. This study suggests that adductor magnus has at least two functionally unique regions. Differences were most evident during rotation. The different direction-specific actions may imply that each segment performs separate roles in hip stability and movement. These findings may have implications on injury prevention and rehabilitation for adductor-related groin injuries, hamstring strain injury, and hip pathology. Clin. Anat. 31:535-543, 2018. © 2018 Wiley Periodicals, Inc.

Intramuscular Pressure of Tibialis Anterior Reflects Ankle Torque but Does Not Follow Joint Angle-Torque Relationship

Intramuscular pressure (IMP) is the hydrostatic fluid pressure that is directly related to muscle force production. Electromechanical delay (EMD) provides a link between mechanical and electrophysiological quantities and IMP has potential to detect local electromechanical changes. The goal of this study was to assess the relationship of IMP with the mechanical and electrical characteristics of the tibialis anterior muscle (TA) activity at different ankle positions. We hypothesized that (1) the TA IMP and the surface EMG (sEMG) and fine-wire EMG (fwEMG) correlate to ankle joint torque, (2) the isometric force of TA increases at increased muscle lengths, which were imposed by a change in ankle angle and IMP follows the length-tension relationship characteristics, and (3) the electromechanical delay (EMD) is greater than the EMD of IMP during isometric contractions. Fourteen healthy adults [7 female; mean (SD) age = 26.9 (4.2) years old with 25.9 (5.5) kg/m2 body mass index] performed (i) three isometric dorsiflexion (DF) maximum voluntary contraction (MVC) and (ii) three isometric DF ramp contractions from 0 to 80% MVC at rate of 15% MVC/second at DF, Neutral, and plantarflexion (PF) positions. Ankle torque, IMP, TA fwEMG, and TA sEMG were measured simultaneously. The IMP, fwEMG, and sEMG were significantly correlated to the ankle torque during ramp contractions at each ankle position tested. This suggests that IMP captures in vivo mechanical properties of active muscles. The ankle torque changed significantly at different ankle positions however, the IMP did not reflect the change. This is explained with the opposing effects of higher compartmental pressure at DF in contrast to the increased force at PF position. Additionally, the onset of IMP activity is found to be significantly earlier than the onset of force which indicates that IMP can be designed to detect muscular changes in the course of neuromuscular diseases impairing electromechanical transmission.

Subacromial impingement syndrome: An electromyographic study of shoulder girdle muscle fatigue

Muscle fatigue affecting glenohumeral and/or scapular muscles is suggested as one of the contributing factors to the development of subacromial impingement syndrome (SAIS). Nonetheless, the fatigability of shoulder girdle muscles in association with the pathomechanics of SAIS has not been reported. This study aimed to measure and compare fatigue progression within the shoulder girdle musculature of patients and healthy controls. 75 participants including 39 patients (20 females; 19 males) and 36 healthy controls (15 females; 21 males) participated in the study. Study evaluated the progression of muscle fatigue in 15 shoulder girdle muscles by means of surface and fine-wire EMG during submaximal contraction of four distinct movements (abduction, flexion, internal and external rotation). Shoulder strength, subjective pain experience (McGill Pain Questionnaire), and psychological status (Hospital Anxiety and Depression Scale) were also assessed. The results were compared between patient and control groups according to the gender. Despite marked fatigue observed in the majority of muscles particularly during flexion and abduction at 90°, overall results indicated a lower tendency of fatigue progression in the impingement group across the tests (p < 0.05 – p < 0.001). Shoulder Strength, pain experience, and psychological status were significantly different between the two groups (P < .05). Lower tendency to fatigue progression in the impingement group can be attributed to the presence of fear avoidance and pain-related muscle inhibition, which in turn lead to adaptations in motor programme to reduce muscle recruitment and activation. The significantly higher levels of pain experience and anxiety/depression in the impingement group further support this proposition.

The influence of foot position on lower leg muscle activity during a heel raise exercise measured with fine-wire and surface EMG

ObjectiveExercises for lower leg muscles are important to improve function. To examine the influence of foot position on lower leg muscle activity during heel raises. DesignCross-sectional laboratory study. SettingLaboratory. ParticipantsFourteen healthy men participated in this study. Main outcome measuresThe muscle activity levels of the tibialis posterior (TP), peroneus longus (PL), flexor digitorum longus (FDL) and medial gastrocnemius (MG) were measured. The heel raises consisted of three foot positions: 1) neutral, 2) 30° abduction, and 3) 30° adduction. The EMG data for five repetitions of each foot position were normalized to maximum voluntary contraction. One-way repeated measure ANOVA was employed for statistical analysis. ResultsThe muscle activity level of TP, PL and FDL was significantly different between the three foot positions during the heel raises. TP and FDL showed the highest activity level in 30° foot adduction while PL demonstrated the highest activity level in 30° foot abduction. ConclusionsHeel raises with 30° foot adduction and abduction positions can change lower leg muscle activity; These findings suggest that altering foot posture during the heel raise exercise may benefit patients with impaired TP, PL or FDL function.

Are chronic neck pain, scapular dyskinesis and altered scapulothoracic muscle activity interrelated?: A case-control study with surface and fine-wire EMG

ObjectivesThe function of the scapula is important in normal neck function and might be disturbed in patients with neck pain. The surrounding muscular system is important for the function of the scapula. To date, it is not clear if patients with idiopathic neck pain show altered activity of these scapulothoracic muscles. Therefore, the objective of this study was to investigate differences in deeper and superficial lying scapulothoracic muscle activity between patients with idiopathic neck pain and healthy controls during arm elevation, and to identify the influence of scapular dyskinesis on muscle activity. MethodsScapular dyskinesis was rated with the yes/no method. The deeper lying (Levator Scapulae, Pectoralis Minor (Pm) and Rhomboid major) and superficial lying (Trapezius and Serratus Anterior) scapulothoracic muscles’ activity was investigated with fine-wire and surface EMG, respectively, in 19 female subjects with idiopathic neck pain (age 28.3±10.1years, average duration of neck pain 45.6±36.3months) and 19 female healthy control subjects (age 29.3±11.7years) while performing scaption and towel wall slide. Possible interactions or differences between subject groups, scapular dyskinesis groups or phases of the task were studied with a linear mixed model. ResultsHigher Pm activity during the towel wallslide (p=0.024, mean difference 8.8±3.3% MVIC) was shown in patients with idiopathic neck pain in comparison with healthy controls. For the MT, a significant group∗dyskinesis interaction effect was found during scaption which revealed that patients with neck pain and scapular dyskinesis showed lower Middle Trapezius (MT) activity in comparison with healthy controls with scapular dyskinesis (p=0.029, mean difference 5.1±2.2% MVIC). ConclusionsIn the presence of idiopathic neck pain, higher Pm activity during the towel wallslide was found. Patients with neck pain and scapular dyskinesis showed lower MT activity in comparison with healthy controls with scapular dyskinesis during scaption. Scapular dyskinesis did not have a significant influence on scapulothoracic muscle activity.

Pattern of activation of pelvic floor muscles in men differs with verbal instructions.

To investigate the effect of instruction on activation of pelvic floor muscles (PFM) in men as quantified by transperineal ultrasound imaging (US) and to validate these measures with invasive EMG recordings. Displacement of pelvic floor landmarks on transperineal US, intra-abdominal pressure (IAP) recorded with a nasogastric transducer, and surface EMG of the abdominal muscles and anal sphincter were recorded in 15 healthy men during sub-maximal PFM contractions in response to different verbal instructions: "tighten around the anus," "elevate the bladder," "shorten the penis," and "stop the flow of urine." In three men, fine-wire EMG recordings were made from puborectalis and bulbocavernosus, and trans-urethral EMG recordings from the striated urethral sphincter (SUS). Displacement data were validated by analysis of relationship with invasive EMG. Displacement, IAP, and abdominal/anal EMG were compared between instructions. Displacement of pelvic landmarks correlated with the EMG of the muscles predicted anatomically to affect their locations. Greatest dorsal displacement of the mid-urethra and SUS activity was achieved with the instruction "shorten the penis." Instruction to "elevate the bladder" induced the greatest increase in abdominal EMG and IAP. "Tighten around the anus" induced greatest anal sphincter activity. The pattern of urethral movement measured from transperineal US is influenced by the instructions used to teach activation of the pelvic floor muscles in men. Efficacy of PFM training may depend on the instructions used to train activation. Instructions that optimize activation of muscles with a potential to increase urethral pressure without increasing abdominal EMG/IAP are likely ideal. Neurourol. Urodynam. 35:457-463, 2016. © 2015 Wiley Periodicals, Inc.

The use of fine-wire EMG to investigate shoulder muscle recruitment patterns during cello bowing: The results of a pilot study

The physical mechanics of music making is important both in the prevention of injuries and in guiding how music is performed and taught. Electromyography has potential as a resource in understanding the loads involved in instrumental playing; however, only a small number of projects have been undertaken, and little is understood on the muscle activity used during bowing on string instruments. This study aimed to measure the muscle activity at the bowing shoulder of a cellist during cello playing and to establish if fine-wire EMG is useful in understanding muscle recruitment in string players without interfering with normal playing ability. This project used a combination of fine-wire and surface EMG to evaluate the muscular load placed on the right shoulder of a professional cellist whilst playing a set of various bowing exercises. The results indicated that different bowing techniques produced statistically different muscle activity levels, with the supraspinatus muscle in particular maintaining higher mean contraction (20% MVC) during all bowing patterns tested. Fine-wire EMG was useful in measuring shoulder muscle load and did not interfere with normal playing technique of the subject. Overall, the study presents a working protocol from which future studies may be able conduct further research.

Muscle activation patterns in patients with recurrent shoulder instability

Purpose:The aim of this study is to present muscle patterns observed with the direction of instability in a series of patients presenting with recurrent shoulder instability.Materials and Methods:A retrospective review was carried out on shoulder instability cases referred for fine wire dynamic electromyography (DEMG) studies at a specialist upper limb centre between 1981 and 2003. An experienced consultant clinical neurophysiologist performed dual needle insertion into four muscles (pectoralis major (PM), latissimus dorsi (LD), anterior deltoid (AD) and infraspinatus (IS)) in shoulders that were suspected to have increased or suppressed activation of muscles that could be contributing to the instability. Raw EMG signals were obtained while subjects performed simple uniplanar movements of the shoulder. The presence or absence of muscle activation was noted and compared to clinical diagnosis and direction of instability.Results:A total of 140 (26.6%) shoulders were referred for fine wire EMG, and 131 studies were completed. Of the shoulders tested, 122 shoulders (93%) were identified as having abnormal patterns and nine had normal patterns. PM was found to be more active in 60% of shoulders presenting with anterior instability. LD was found to be more active in 81% of shoulders with anterior instability and 80% with posterior instability. AD was found to be more active in 22% of shoulders with anterior instability and 18% with posterior instability. IS was found to be inappropriately inactive in only 3% of shoulders with anterior instability but in 25% with posterior instability. Clinical assessment identified 93% of cases suspected to have muscle patterning, but the specificity of the clinical assessment was only correct in 11% of cases.Conclusion:The DEMG results suggest that increased activation of LD may play a role in both anterior and posterior shoulder instability; increased activation of PM may play a role in anterior instability.

EMG of the hip adductor muscles in six clinical examination tests

ObjectivesTo assess activation of muscles of hip adduction using EMG and force analysis during standard clinical tests, and compare athletes with and without a prior history of groin pain. Study designControlled laboratory study. Participants21 male athletes from an elite junior soccer program. Main outcome measuresBilateral surface EMG recordings of the adductor magnus, adductor longus, gracilis and pectineus as well as a unilateral fine-wire EMG of the pectineus were made during isometric holds in six clinical examination tests. A load cell was used to measure force data. ResultsTest type was a significant factor in the EMG output for all four muscles (all muscles p < 0.01). EMG activation was highest in Hips 0 or Hips 45 for adductor magnus, adductor longus and gracilis. EMG activation for pectineus was highest in Hips 90. Injury history was a significant factor in the EMG output for the adductor longus (p < 0.05), pectineus (p < 0.01) and gracilis (p < 0.01) but not adductor magnus. For force data, clinical test type was a significant factor (p < 0.01) with Hips 0 being significantly stronger than Hips 45, Hips 90 and Side lay. BMI (body mass index) was a significant factor (p < 0.01) for producing a higher force. All other factors had no significant effect on the force outputs. ConclusionsHip adduction strength assessment is best measured at hips 0 (which produced most force) or 45° flexion (which generally gave the highest EMG output). Muscle EMG varied significantly with clinical test position. Athletes with previous groin injury had a significant fall in some EMG outputs.

Firing duration of masseter motor units during prolonged low-level contractions

Objective The study aimed to determine whether motor units (MUs) of the masseter muscle can be continuously active during a prolonged low-level sustained contraction. Methods Intramuscular fine-wire EMG activity was recorded unilaterally from the masseter muscles of 13 pain-free volunteers (mean age ± SD = 26.7 ± 7.7 years), during low-level biting tasks performed for 30 min. The stored intramuscular EMG signals were decomposed into individual MU action-potential trains using long-term decomposition software. Depending on relative duration of the MU activity, MUs were classified as sporadically (<50% of the time), intermittently (50% ⩽ time ⩽ 95%), or continuously active (>95% of the time). Results The overall number of MUs identified during the low-level biting task was 203. Of these, nine continuously active MUs (4.4%) were found in six of the 13 subjects investigated, whereas 50 intermittent MUs (24.6%) were found in 12 subjects. The remaining MUs (71.0%) were sporadically active and were found in all of the subjects investigated. Conclusion The majority of masseter MUs is sporadically or intermittently active during prolonged low-level contractions, but some of them can also be continuously active. Significance Sustained clenching efforts may be accompanied by continuous activity of a few selected muscle fibres.

Traumatic pneumothorax sustained via fine-wire electromyography insertion at the shoulder

A 29-year-old male consented to participate in a research roject utilising fine-wire EMG of the supraspinatus, subcapularis and rhomboid major muscles, along with surface MG of several other shoulder muscles. The participant eighed 63 kg, was 1.76 m in height and had a body mass ndex of 20.3 kg/m2. There was no history of pulmonary athology or shoulder orthopaedic injury. The testing protocol included throwing accuracy, scapuar kinematics, isokinetic shoulder assessments and EMG nalysis during functional elevation tasks. Two intramuscular ne-wire electrode insertions were performed for each musle tested according to recommended guidelines [2,3]. The articipant reported sharp pain (7/10) upon insertion of the eedle into the rhomboid muscle. The pain was indicated to e posterior, approximately over the inferior third of the right

Motor Unit Conduction Velocity during Sustained Contraction after Eccentric Exercise

Eccentric contractions induce muscle fiber damage that is associated with a decreased capacity to generate voluntary force and increased fiber membrane permeability. Changes in fiber membrane permeability results in cell depolarization that is expected to have an effect on the action potential propagation velocity of the muscle fibers. The aim of the study was to investigate the action potential propagation velocity in individual motor units before and 24 and 48 h after eccentric exercise. Multichannel surface and fine-wire intramuscular EMG signals were concurrently recorded from two locations of the right vastus medialis muscle of 10 healthy men during 60-s isometric contractions at 10% and 30% of the maximal force. The maximal force decreased by 26.1 ± 16.1% (P < 0.0001) at 24 h and remained reduced by 23.6 ± 14.5% (P < 0.0001) 48 h after exercise with respect to baseline. With respect to baseline, motor unit conduction velocity decreased (P < 0.05) by (average over 24 and 48 h after exercise) 7.7 ± 2.7% (10% maximal voluntary contraction (MVC), proximal), 7.2 ± 2.8% (10% MVC, distal), 8.6 ± 3.8% (30% MVC, proximal), and 6.2 ± 1.5% (30% MVC, distal). Moreover, motor unit conduction velocity decreased over time during the sustained contractions at faster rates when assessed 24 and 48 h after exercise with respect to baseline for both contraction forces and locations (P < 0.05). These results indicate that the electrophysiological membrane properties of muscle fibers are altered by exercise-induced muscle fiber damage.