Comparison Of Muscle Activity Research Articles

Relating neuromuscular control to functional anatomy of limb muscles in extant archosaurs.

Electromyography (EMG) is used to understand muscle activity patterns in animals. Understanding how much variation exists in muscle activity patterns in homologous muscles across animal clades during similar behaviours is important for evaluating the evolution of muscle functions and neuromuscular control. We compared muscle activity across a range of archosaurian species and appendicular muscles, including how these EMG patterns varied across ontogeny and phylogeny, to reconstruct the evolutionary history of archosaurian muscle activation during locomotion. EMG electrodes were implanted into the muscles of turkeys, pheasants, quail, guineafowl, emus (three age classes), tinamous and juvenile Nile crocodiles across 13 different appendicular muscles. Subjects walked and ran at a range of speeds both overground and on treadmills during EMG recordings. Anatomically similar muscles such as the lateral gastrocnemius exhibited similar EMG patterns at similar relative speeds across all birds. In the crocodiles, the EMG signals closely matched previously published data for alligators. The timing of lateral gastrocnemius activation was relatively later within a stride cycle for crocodiles compared to birds. This difference may relate to the coordinated knee extension and ankle plantarflexion timing across the swing-stance transition in Crocodylia, unlike in birds where there is knee flexion and ankle dorsiflexion across swing-stance. No significant effects were found across the species for ontogeny, or between treadmill and overground locomotion. Our findings strengthen the inference that some muscle EMG patterns remained conservative throughout Archosauria: for example, digital flexors retained similar stance phase activity and M. pectoralis remained an 'anti-gravity' muscle. However, some avian hindlimb muscles evolved divergent activations in tandem with functional changes such as bipedalism and more crouched postures, especially M. iliotrochantericus caudalis switching from swing to stance phase activity and M. iliofibularis adding a novel stance phase burst of activity.

Altered muscle activation patterns (AMAP): an analytical tool to compare muscle activity patterns of hemiparetic gait with a normative profile

BackgroundStroke survivors often have lower extremity sensorimotor impairments, resulting in an inability to sufficiently recruit muscle activity at appropriate times in a gait cycle. Currently there is a lack of a standardized method that allows comparison of muscle activation in hemiparetic gait post-stroke to a normative profile.MethodsWe developed a new tool to quantify altered muscle activation patterns (AMAP). AMAP accounts for spatiotemporal asymmetries in stroke gait by evaluating the deviations of muscle activation specific to each gait sub-phase. It also recognizes the characteristic variability within the healthy population. The inter-individual variability of normal electromyography (EMG) patterns within some sub-phases of the gait cycle is larger compared to others, therefore AMAP penalizes more for deviations in a gait sub-phase with a constant profile (absolute active or inactive) vs variable profile. EMG data were collected during treadmill walking, from eight leg muscles of 34 stroke survivors at self-selected speeds and 20 healthy controls at four different speeds. Stroke survivors’ AMAP scores, for timing and amplitude variations, were computed in comparison to healthy controls walking at speeds matched to the stroke survivors’ self-selected speeds.ResultsAltered EMG patterns in the stroke population quantified using AMAP agree with the previously reported EMG alterations in stroke gait that were identified using qualitative methods. We defined scores ranging between ±2.57 as “normal”. Only 9% of healthy controls were outside “normal” window for timing and amplitude. Percentages of stroke subjects outside the “normal” window for each muscle were, Soleus = 79%; 73%, Medial Gastrocnemius = 62%; 79%, Tibialis Anterior = 62%; 59%, and Gluteus Medius = 48%; 51% for amplitude and timing component respectively, alterations were relatively smaller for the other four muscles. Paretic-propulsion was negatively correlated to AMAP scores for the timing component of Soleus. Stroke survivors’ self-selected walking speed was negatively correlated with AMAP scores for amplitude and timing of Soleus but only amplitude of Medial gastrocnemius (p < 0.05).ConclusionsOur results validate the ability of AMAP to identify alterations in the EMG patterns within the stroke population and its potential to be used to identify the gait phases that may require more attention when developing an optimal gait training paradigm.Trial registrationClinicalTrials.govNCT00712179, Registered July 3rd 2008

The Treadport: Natural Gait on a Treadmill

To evaluate the differences between walking on an advanced robotic locomotion interface called the Treadport and walking overground with healthy subjects. Previous studies have compared treadmill-based and overground walking in terms of gait parameters. The Treadport's unique features including self-selected speed capability, large belt, kinesthetic force feedback, and virtual reality environment distinguish it from other locomotion interfaces and could provide a natural walking experience for the users. Young, healthy subjects (N = 17) walked 10 meters 10 times each for both overground and the Treadport environments. Comparison between walking conditions used spatiotemporal and kinematic parameters. In addition, electromyographic data was collected for five of the 17 subjects to compare muscle activity between the two conditions. Gait on the Treadport was found to have no significant differences (p > .05) with overground walking in terms of hip and knee joint angles, cadence and stride length and stride speed, and muscle activation of the four muscle groups measured. Differences (p < .05) were observed in ankle dorsiflexion which was reduced by 2.47 ± 0.01 degrees on the Treadport. Walking overground and on the Treadport is highly correlated and not significantly different in 13 of 14 parameters. This study suggests that the Treadport creates an environment for natural walking experience, where natural gait of users is almost preserved, with great potential to be useful for other applications, such as gait rehabilitation of individuals with walking impairments.

Comparison of lower limb muscle activation according to horizontal whole-body vibration frequency and knee angle

Whole-body vibration refers to an exercise that stimulates the muscles, using a vibration with an amplitude and power, however, there are few studies that have dealt with fundamental questions such as optimal frequency or body position. This study aims to compare lower limb activation, according to horizontal whole-body vibration frequency and knee flexion angle, in healthy adults. Using 18 healthy adults aged 21–30, this study measured and analysed the activities of the vastus lateralis (VL), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GCM) muscles, for different horizontal whole-body vibration frequencies (0 Hz, 2 Hz, and 4 Hz) and knee flexion angles (0°, 30°, and 60°), using surface electromyography (sEMG). There was a statistically significant increase in lower limb muscle activation according to horizontal whole-body vibration frequency and knee flexion angle: comparing muscle activation with frequency, the muscle activation of VL, BF, TA, and GCM increased with increase in frequency (p<0.05). The muscle activation of VL and TA increased with increase in knee flexion angle (p<0.05). In this study, it was observed that for whole-body vibration provided in a horizontal direction, larger the frequency and higher the knee flexion angle, greater the lower limb activation.

Effect of Scapular Downward Rotator Stretch Exercises on Scapular Upward Rotator Activity During Arm Elevation in Subjects with Scapular Downward Rotation Syndrome

The purpose of this study was to investigate the effects of scapular downward rotator stretch exercises on muscle activity of the scapular upward rotators during arm elevation in subjects with scapular downward rotation syndrome. Sixteen people with scapular downward rotation syndrome were participated. To investigate the effectiveness of these stretching exercises, the surface electromyography (EMG) activity of levator scapula, upper trapezius, lower trapezius, and serratus anterior was measured at shoulder flexions of 90°, 120°, and 150° pre-and post-exercise. Two-way repeated-measures analysis of variance was used to determine the changes in muscle activities. A Bonferroni correction was performed on the post hoc test (α = 0.017). The activity of the levator scapular, upper trapezius, and serratus anterior muscle was increased (p < 0.017) as shoulder flexion angle changed. A comparison of muscle activity pre-and post-exercise and at different shoulder flexion angles showed that levator scapular and upper trapezius muscle activity was decreased at a shoulder flexion of 150° (p < 0.017). Serratus anterior muscle activity was decreased at shoulder flexion of 120° and 150° (p < 0.017). This study suggests that scapular downward rotator muscle stretching exercises should be performed before strengthening exercises to improve mobility in people with scapular downward rotation syndrome.

Influence of muscle activation of posterior oblique sling from changes in activation of gluteus maximus from exercise of prone hip extension of normal adult male and female.

[Purpose] There have been many study ipsilateral erector spinae in regard of prone hip extension (PHE). However, mediating methods have been focusing on the reinforcement of gluteus. Hereupon, this study is intended to identify how an increase of gluteus maximus influences on posterior oblique sling (POS) and suggest a mediating method to effectively reinforce them. This study shows the seclective POS strength exercise. [Participants and Methods] This study has been conducted on normal male (13) and female (13), and participants were asked to proceed PHE exercise and prone hip extension with hip abduction with knee flexion (PHEAKF). Surface electromyography (EMG) was recorded from the contralateral latissimus dorsi, contralateral erector spinae, ipsilateral erector spinae, ipsilateral gluteus maximus, and ipsilateral biceps femoris. A paried t-test was used to compare muscle activity POS. [Results] EMG activity of the contralateral latissimus dorsi, ipsilateral erector spinae, and ipsilateral gluteus maximus was significantly greater performed PHEAKF than PHE. As for ipsilateral biceps femoris, muscle activation was lower in PHEAKF than PHE. [Conclusions] According to the results of this study, increase in muscular activation from the direction of muscular fiber and posterior oblique sling seems to be an important factor that influencontralateral crector spinae on muscular activation of POS.

Correlation between Pelvic Tilt Angle and Erector Spinae

Background/Objectives: The purpose of this study was to investigate the activity of the spinal muscles according to the pelvic tilt angle and to identify the muscles affecting the posture. Methods/Statistical analysis:Thirty healthy young adults participated in this study. The muscle activity and pelvic tilting of the erector spinea were measured using electromyography and inertial sensor. One-way repeated ANOVA was used to compare muscle activity of each muscle according to pelvic tilting angle. Findings: The muscle activity of the three muscles of the spine showed a significant difference between posterior tilting and anterior tilting of the pelvic (p<0.05). In other words, it showed higher muscle activity in anterior tiling. Iliocostalis lumborum showed lower muscle activity in the sitting position, although the range of motion of the pelvic was larger in the sitting position than in the standing position. Improvements/Applications: Appropriate muscle activity of the iliocostalis lumborum in the sitting position should be considered for weight-bearing reduction of the lumbar spine and prevention of musculoskeletal disorders of the spine.

Comparison of Muscle Activity in Proximal Muscle of Lower Extremities during Lunge according to the Anterior-posterior Distance of Foot Position

Comparison of Muscle Activity in Proximal Muscle of Lower Extremities during Lunge according to the Anterior-posterior Distance of Foot Position

Comparison of Muscle Activity According to Hip Abduction Angle during Hip Extension Exercise in Prone Position

Comparison of Muscle Activity According to Hip Abduction Angle during Hip Extension Exercise in Prone Position

Spinal control of muscle synergies for adult mammalian locomotion.

The control of locomotion is thought to be generated by activating groups of muscles that perform similar actions, which are termed muscle synergies. Here, we investigated if muscle synergies are controlled at the level of the spinal cord. We did this by comparing muscle activity in the legs of cats during stepping on a treadmill before and after a complete spinal transection that abolishes commands from the brain. We show that muscle synergies were maintained following spinal transection, validating the concept that muscle synergies for locomotion are primarily controlled by circuits of neurons within the spinal cord. Locomotion is thought to involve the sequential activation of functional modules or muscle synergies. Here, we tested the hypothesis that muscle synergies for locomotion are organized within the spinal cord. We recorded bursts of muscle activity in the same cats (n= 7) before and after spinal transection during tied-belt locomotion at three speeds and split-belt locomotion at three left-right speed differences. We identified seven muscles synergies before (intact state) and after (spinal state) spinal transection. The muscles comprising the different synergies were the same in the intact and spinal states as well as at different speeds or left-right speed differences. However, there were some significant shifts in the onsets and offsets of certain synergies as a function of state, speed and left-right speed differences. The most notable difference between the intact and spinal states was a change in the timing between the knee flexor and hip flexor muscle synergies. In the intact state, the knee flexor synergy preceded the hip flexor synergy, whereas in the spinal state both synergies occurred concurrently. Afferent inputs also appear important for the expression of some muscle synergies, specifically those involving biphasic patterns of muscle activity. We propose that muscle synergies for locomotion are primarily organized within the spinal cord, although their full expression and proper timing requires inputs from supraspinal structures and/or limb afferents.

Comparison of muscle activity from upper trapezius and wrist extensors between dominant and non-dominant upper limbs during computer-based tasks.

Sustained low-level muscle activity occurring during computer-based tasks is associated with the development of WMSDs (work-related musculoskeletal disorders) and this biomechanical exposure may be different between limbs. To compare muscle activity from dominant and non-dominant upper trapezius (UT) and wrist extensors (WE) during computer-based tasks in real work settings. Forty-five workers were monitored during two hours while performing their usual administrative tasks. Surface electromyography (sEMG) was recorded from UT and WE muscles in both sides. Rest and general exposure variables were calculated. The 50th percentile demonstrated little muscle activity demand, for both dominant and non-dominant UT and no difference between sides was observed. The dominant WE muscles had lower measures of rest and higher muscle activity when compared with the non-dominant side. Differences in sEMG between upper limbs were only found in WE muscles, probably due to the use of the mouse. The overall low-level muscle activity suggests a constant activation of the same motor units for the entire data-collection period, which can be considered harmful for musculoskeletal health.

A Comparison of Muscle Activation during the Pull-up and Three Alternative Pulling Exercises

Journal of Physical Fitness, Medicine & Treatment in Sports is an interdisciplinary open access peer reviewed journal that publishes original research, reviews, short communication, case reports, news, commentaries etc., in the field of sports medicine, treatment and exercise medication.

Stationary Exercise in Overweight and Normal Weight Children.

This study examined differences in lower extremity kinematics and muscle activation patterns between normal weight (NW) and overweight (OW) children during stationary exercises (running in place, frontal kick, and butt kick) at submaximal intensity. Healthy children (aged 10-13y) were stratified into OW (n = 10; body fat percentage: 34.97 [8.60]) and NW (n = 15; body fat percentage: 18.33 [4.87]). Electromyography was recorded for rectus femoris, vastus lateralis, biceps femoris, gastrocnemius, and tibialis anterior. In addition, the ratings of perceived exertion and range of motion of hip, knee, and ankle joints were collected during stationary exercises. Repeated-measures analysis of variance compared muscle activation, range of motion, and ratings of perceived exertion between groups and exercises. Friedman test examined sequencing of muscles recruitment. Compared with NW, OW experienced significantly greater ratings of perceived exertion (13.7 [0.8] vs 11.7 [0.7]; P < .001) and electromyography amplitude in all muscles apart from vastus lateralis during stationary exercises. In addition, NW children used more consistent muscles' recruitment pattern in comparison with OW children. The range of motion was similar between groups at all joints. OW children may adopt a more active neuromuscular strategy to provide greater stability and propulsion during stationary exercises. Stationary exercise can be prescribed to strengthen lower extremity muscles in OW children, but mode and intensity must be considered.

Efeito da bandagem elástica na ativação muscular e torque isométrico dos extensores do joelho em indivíduos com osteoartrite

A osteoartrite é uma doença articular crônica, caracterizada por uma degeneração progressiva da cartilagem articular, que resulta em incapacidade funcional. Entre as articulações acometidas, o joelho é a mais afetada devido à sobrecarga mecânica imposta a essa articulação nas atividades diárias. A osteoartrite de joelho é considerada uma das formas clínicas mais incapacitantes da doença. O objetivo deste estudo foi verificar o efeito da bandagem elástica (BE) na ativação muscular do quadríceps e no torque isométrico dos extensores de joelho em indivíduos com Osteoartrite de Joelho. Participaram do estudo 13 voluntárias (64,5 ± 7,2 anos) do sexo feminino, com diagnóstico radiológico de osteoartrite de joelho. Os procedimentos de coleta de dados foram realizados em três dias, com intervalo de sete dias entre eles. As voluntárias foram avaliadas em três diferentes condições: sem BE, BE placebo e BE ativação. Foram realizadas as avaliações do torque isométrico extensor do joelho e ativação eletromiográfica dos músculos reto femoral, vasto medial e vasto lateral por meio da eletromiografia de superfície. Para análise estatística foi adotado o teste ANOVA Medidas Repetidas, considerando nível de significância de p &lt; 0,05. Os resultados mostraram que não houve diferença significativa para comparação da ativação muscular e torque entre as condições analisadas (p = 0,556). Conclui-se que a BE não foi capaz de promover uma alteração no recrutamento muscular e torque isométrico de quadríceps em indivíduos com osteoartrite de joelho.

Electromyographic Analysis of Gluteus Maximus, Gluteus Medius, and Tensor Fascia Latae During Therapeutic Exercises With and Without Elastic Resistance

Strengthening and activation of the gluteus maximus and gluteus medius while minimizing the contribution of the tensor fascia latae are important components in the treatment of many lower limb injuries. Previous researchers have evaluated a myriad of exercises that activate the gluteus maximus (GMax) and gluteus medius (GMed), however, limited research has been performed describing the role of the addition of elastic resistance to commonly used exercises. The primary purpose of this study was to determine the gluteal-to-tensor fascia latae muscle activation (GTA index) and compare electromyographic muscle activation of the GMax, GMed, and TFL while performing 13 commonly prescribed exercises designed to target the GMax and GMed. The secondary purpose of this study was to compare muscle activation of the GMax, GMed, and TFL while performing a subgroup of three matched exercises with and without elastic resistance. Repeated measures cohort study. A sample of 11 healthy, physically active male and females, free of low back pain and lower extremity injuries, were recruited for the study. Surface electromyography was used to quantify the normalized EMG activation of the gluteus maximus, gluteus medius, and tensor fascia latae while performing 13 exercises. Three of these exercises were performed with and without elastic resistance. The maximal voluntary isometric contraction was established for each muscle and order in which the exercises were performed was randomized to minimize the effect of fatigue. The relative activation of the gluteal muscles were compared to the tensor fascia latae and expressed as the GTA index. Clams with and without resistance, running man gluteus maximus exercise on the stability trainer, and bridge with resistance, generated the highest GTA index respectively. Significant differences in activation of the TFL occurred between clams with and without resistance. The findings are consistent with those of previous investigators who reported that the clam exercise optimally activated the gluteal muscles while minimizing tensor fascia latae activation. Level 2b.

COMPARISON OF BILATERAL AND UNILATERAL SQUAT EXERCISES ON BARBELL KINEMATICS AND MUSCLE ACTIVATION

Bilateral squats are commonly used in lower body strength training programs, while unilateral squats are mainly used as additional or rehabilitative exercises. Little has been reported regarding the kinetics, kinematics and muscle activation in unilateral squats in comparison to bilateral squats. Therefore, the purpose of this study was to compare muscle activity, kinetics, and barbell kinematics between unilateral and bilateral squats with the same external load per leg in experienced resistance-trained participants. Fourteen resistance-trained males (age 23 ± 4years, body mass 80.5 ± 8.5kg and height 1.81 ± 0.06m) participated. Barbell kinematics and surface electromyography (EMG) activity of eleven muscles were measured during the descending and ascending phase of each repetition of the squat exercises. Total lifting time was longer and average and peak velocity were lower for the bilateral squat (p<0.001). Furthermore, higher muscle activity was found in the three quadriceps muscles, biceps femoris (ascending phase) and the erector spinae (ascending phase) in the bilateral squat, while greater activation for the semitendinosis (descending phase) (p=0.003) was observed for the unilateral squat with foot forwards. In the ascending phase, the prime movers showed increased muscle activity with repetition from repetition 1 to 4 (p≤0.034). Unilateral squats with the same external load per leg produced greater peak vertical ground reaction forces than bilateral squats, as well as higher barbell velocity, which is associated with strength development and rate of force development, respectively. The authors suggest using unilateral rather than bilateral squats for people with low back pain and those enrolled in rehabilitation programs after ACL ruptures, as unilateral squats are performed with small loads (28 vs. 135 kg) but achieve similar magnitude of muscle activity in the hamstring, calf, hip and abdominal muscles and create less load on the spine. 1b.

Ankle perturbation generates bilateral alteration of knee muscle onset times after unilateral anterior cruciate ligament reconstruction.

BackgroundThe aim of this study was to compare muscle activation onset times of knee muscles between the involved and uninvolved knee of patients with unilateral anterior cruciate ligament reconstruction (ACLR), and the uninjured knees of healthy subjects after a controlled perturbation at the ankle level.MethodsFifty male amateur soccer players, 25 with unilateral ACLR using semitendinosus-gracilis graft (age = 28.36 ± 7.87 years; time after surgery = 9 ± 3 months) and 25 uninjured control subjects (age = 24.16 ± 2.67 years) participated in the study. Two destabilizing platforms (one for each limb) generated a controlled perturbation at the ankle of each participant (30°of inversion, 10°plantarflexion simultaneously) in a weight bearing condition. The muscle activation onset times of semitendinosus (ST) and vastus medialis (VM) was detected through an electromyographic (EMG) analysis to assess the neuromuscular function of knee muscles.ResultsSubjects with ACLR had significant delays in EMG onset in the involved (VM = 99.9 ± 30 ms; ST = 101.7 ± 28 ms) and uninvolved knee (VM = 100.4 ± 26 ms; ST = 104.7 ± 28 ms) when compared with the healthy subjects (VM = 69.1 ± 9 ms; ST = 74.6 ± 9 ms). However, no difference was found between involved and uninvolved knee of the ACLR group.DiscussionThe results show a bilateral alteration of knee muscles in EMG onset after a unilateral ACLR, responses that can be elicited with an ankle perturbation. This suggests an alteration in the central processing of proprioceptive information and/or central nervous system re-organization that may affect neuromuscular control of knee muscles in the involved and uninvolved lower limbs.

Study of muscle activation during in-water gait of SCI patients using surface EMG

We compared muscle activation during in- and out-of-water gait of SCI patients to understand the influence of the aquatic ambient on rehabilitation programme. Twenty healthy subjects and 20 SCI patients were enrolled. All patients had retained walking ability (AIS C and D, lesion level C4-L2, age 18–70 years) and could ambulate indipendently for a minimum of 5 m with or without walking aids. We analyzed, with an surface 8 channel wireless EMG, the following muscles of the right leg: rectus femoris, vastus medialis, vastus lateralis, gluteus maximus, gluteus medius, biceps femoris, tibialis anterior, gastrocnemius medialis. In both healthy and affected subjects in water the walking speed decreases whereas the duration of gait cycle increases. Furthermore in SCI patients we found out an increase of the swing phase. Comparing in- and out-of-water results for SCI subjects the maximum muscle activation peak in water occurred before than on dry land; at the opposite in healthy subjects we registered that the maximum muscle activation peak occurred earlier out of the pool. The in-water gait cycle is much more similar between SCI and healthy subjects than the out-of-water one. These results suggest that aquatic ambient could positively influence muscle recruitment in SCI patient. Moreover these data give us the opportunity to design water-based exercises that can enrich the tailored rehabilitation programme for every patient.

Impact of different EMG normalisation methods on muscle activations and cocontraction index in adults with chronic post-stroke hemiparesis

EMG normalisation is a key step to draw definite conclusions on physiologically standardized data. In the absence of a consensus in scientific literature, recommendations would be useful for the choice of EMG normalisation method in patients, such as hemiparetics, who present atypical EMG patterns during motor behavior. The aim of this work was to compare muscle activations and cocontraction index (CCI) using different EMG normalisation methods during active elbow extension in healthy participants and patients with chronic post-stroke hemiparesis. Four adults with chronic post-stroke hemiparesis (Hemi) and five healthy participants (Co) were included. Elbow kinematics and EMG activity of elbow flexors and triceps brachii were recorded during active elbow extensions performed at spontaneous speed. EMG signal was normalised in reference to EMG activity recorded during isometric or isokinetic MVC. Normalised EMG during elbow extension was used to compute muscle activations and CCI, during the acceleration and deceleration phases. Friedman tests were performed with two factors (group and normalisation). No differences were found between normalisation methods neither for muscle activations and for the cocontraction index in Co and Hemi groups. Greater muscle activations were found in Hemi vs. Co (24.2 ± 13.4% vs. 4.3 ± 3% and 52.4 ± 33.2% vs. 6.2 ± 4.3% during acceleration and deceleration phase, respectively). Cocontraction index in acceleration phase was greater in Hemi vs. Co ( P < 0.05), and in Co between acceleration and decceleration phases ( P < 0.05) ( Fig. 1 ). Even if isokinetic MVC-based EMG normalisation accounts for the influence of angle- and velocity-torque relationships, our results on EMG activations and cocontraction index support the use of isometric instead of isokinetic MVC normalisation, and further suggest the need to take into account individual muscle activations to better understand differences in cocontraction between groups and phases.

Insertion and Presence of Fine-Wire Intramuscular Electrodes to the Lumbar Paraspinal Muscles Do Not Affect Muscle Performance and Activation During High-Exertion Spinal Extension Activities

BackgroundLow back pain (LBP) is commonly associated with paraspinal muscle dysfunctions. A method to study deep lumbar paraspinal (ie, multifidus) muscle function and neuromuscular activation pattern is intramuscular electromyography (EMG). Previous studies have shown that the procedure does not significantly impact muscle function during activities involving low-level muscle contractions. However, it is currently unknown how muscular function and activation are affected during high-exertion contractions. ObjectiveTo examine the effects of insertion and presence of fine-wire EMG electrodes in the lumbar multifidus on muscle strength, endurance, and activation profiles during high-exertion spinal extension muscle contractions. DesignSingle-blinded, repeated measures intervention trial. SettingUniversity clinical research laboratory ParticipantsTwenty individuals between the ages of 18-40 free of recent and current back pain. MethodsMuscle performance was assessed during 3 conditions (with [WI] and without [WO] presence of intramuscular electrodes, and insertion followed by removal [IO]). Isometric spinal extension strength was assessed with a motorized dynamometer. Muscle endurance was assessed using the Sorensen test with neuromuscular activation profiles analyzed during the endurance test. Main Outcome MeasurementsSpinal extensor muscle strength, endurance, and activation. ResultsOur data showed no significant difference in isometric strength (P = .20) between the 3 conditions. A significant difference in muscle endurance was found (P = .03). Post hoc analysis showed that the muscle endurance in the IO condition was significantly higher than the WO condition (161.3 ± 58.3 versus 142.1 ± 48.2 seconds, P = .04), likely due to a learning effect. All 3 conditions elicited minimal pain (range 0-4/10) and comparable muscle activation profiles. ConclusionOur findings suggested the sonographically guided insertion and presence of fine-wire intramuscular EMG electrodes in the lumbar multifidus muscles had no significant impact on spinal extension muscle function. This study provides evidence that implementing intramuscular EMG does not affect muscle performance during high-exertion contractions in individuals with no current back pain. Level of EvidenceII