Peak Electromyography Research Articles

Unilateral Maximum Electromyography Activities When Comparing Isometric Contraction of Hip Abduction between Dominant and Non-Dominant Legs in Healthy College-aged Subjects

The purpose of this study was to compare unilateral surface electromyography (EMG) activities of hip abductor muscles between the dominant and non-dominant leg in college-aged subjects. A total of 13 healthy participants (aged 23.3 ± 3.9 years) volunteered to participated in the study. Subjects performed three 3-second maximal voluntary isometric contractions of the gluteus medius muscle. Subjects were encouraged to maintain an isometric hip abductor contraction at full knee extension. The subjects were positioned on their sides lying on a therapeutic table. Participants were instructed to push out into the pad during each 3-second maximal voluntary isometric contraction trial. The EMG difference of a contraction in the study was evaluated during the experiments. Maximum voluntary isometric contractions of gluteus medius resulted in a significant difference between dominant (4.09 ± 2.0 voltsㆍsec) and non-dominant (3.31 ± 2.0 voltsㆍsec) legs during hip abductions (p 0.05). The maximum peak EMG of gluteus medius demonstrated no significant difference between dominant (5.32 ± 2.0 volts) and non-dominant (5.02 ± 1.9 volts) legs during hip abductions. In conclusion, maximum voluntary isometric contractions of gluteus medius resulted in a significant difference between dominant and non-dominant legs during hip abductions.

Intra-session reliability of electromyographic measurements in flywheel squats.

Although the popularity of flywheel (FW) devices in sports research is increasing, to date, no study has been designed to test the reliability of electromyographic (EMG) variables during FW squats as a basic lower-body FW resistance exercise. At the primary level, our study was conducted to determine the minimum number of the consecutive flywheel (FW) squat repetitions that need to be averaged in a single set to obtain excellent reliability of peak, mean and three position-specific EMG variables. At the secondary level, comprehensive analysis for peak and mean EMG variables was done. Intra-set reliability was investigated using the minimum number of repetitions determined from the primary level of the study. Twenty-six participants performed five sets of seven squats with three FW loads (0.05, 0.125, 0.225 kg∙m2). EMG signals were collected from eight leg muscles. By averaging twelve consecutive repetitions, we obtained ICC2.k > 0.95 for mean and peak EMGRMS regardless of the muscle, load or phase of the squat (concentric vs. eccentric). Due to the heterogeneity of the results at the primary level, position-specific variables were excluded from the inter-set reliability analysis at the secondary level. Trustworthy mean and peak EMG variables from the primary level showed good to excellent inter-set reliability. We suggest averaging twelve consecutive squat repetitions to achieve good to excellent intra-session reliability of EMG variables. By following the proposed protocol, activation of leg muscles can be confidently studied in intra-session repeated-measures study designs.

Influence of Lumbar Mobilizations During the Nordic Hamstring Exercise on Hamstring Measures of Knee Flexor Strength, Failure Point, and Muscle Activity: A Randomized Crossover Trial

ObjectiveThe aims of this study were to quantify the effects of spinal mobilization on force production, failure point, and muscle activity of the hamstrings during the Nordic hamstring exercise (NHE), and to explore individual differences in responses. MethodsIn a replicated randomized crossover trial, 24 asymptomatic, recreationally active men (age [mean ± standard deviation]: 27 ± 6 years; body mass: 82 ± 17 kg; height: 181 ± 8 cm) completed 2 standardized intervention trials (L4/5 zygapophyseal mobilizations) and 2 control trials. The failure point of the NHE was determined with 3D motion capture. Peak force, knee flexor torque, and electromyography (EMG) of the biceps femoris were measured. Data analyses were undertaken to quantify mean intervention response and explore any individual response heterogeneity. ResultsMean (95% confidence interval) left-limb force was higher in intervention than in control trials by 18.7 (4.6-32) N. Similarly, right-limb force was higher by 22.0 (3.4-40.6) N, left peak torque by 0.14 (0.06-0.22) N • m, and right peak torque by 0.14 (0.05-0.23) N • m/kg. Downward force angle was decreased in intervention vs control trials by 4.1° (0.5°-7.6°) on the side of application. Both peak EMG activity (P = .002), and EMG at the downward force (right; P = .020) increased in the intervention condition by 16.8 (7.1-26.4) and 8.8 (1.5-16.1) mV, respectively. Mean downward acceleration angle changed by only 0.3° (−8.9° to 9.4°) in intervention vs control trials. A clear response heterogeneity was indicated only for right force (Participant × Intervention interaction: P = .044; response heterogeneity standard deviation = 34.5 [5.7-48.4] N). Individual response heterogeneity was small for all other outcomes. ConclusionAfter spinal mobilization, immediate changes in bilateral hamstring force production and peak torque occurred during the NHE. The effect on the NHE failure point was unclear. Electromyographic activity increased on the ipsilateral side. Response heterogeneity was generally similar to the random trial-to-trial variability inherent in the measurement of the outcomes.

"NO LOAD" Resistance Training Promotes High Levels of Knee Extensor Muscles Activation-A Pilot Study.

The present article aims to compare electromyographic (EMG) activity of the knee extensors during traditional resistance training (TRT) and no load resistance training with or without visual feedback (NL-VF and NL-NF). Sixteen healthy men (age: 25.2 ± 3.6) volunteered to participate in the study. Participants visited the laboratory on three occasions involving: (1) a 10 repetition maximum test (10 RM test), (2) familiarization and (3) performance of knee extensions using TRT, NL-VF and NL-NF in a random order, with 10 min of rest between them. TRT involved the performance of a set to momentary muscle failure using the 10 RM load. NL-NF involved the performance of 10 repetitions with no external load, but with the intention to maximally contract the muscles during the whole set. NL-VF involved the same procedure as NL-NF, but a monitor was positioned in front of the participants to provide visual feedback on the EMG activity. Peak and mean EMG activity were evaluated on the vastus medialis (VM), vastus lateralis (VL) and rectus femoris (RF). Results: there were no significant differences in VM and VL peak EMG activity among different situations. There was a significant difference for peak EMG activity for RF, where TRT resulted in higher values than NL-VF and NL-NF (p < 0.05). Higher values of mean EMG activity were found for VM, VL and RF during TRT in comparison with both NL-VF and NL-NF. Conclusions: resistance training with no external load produced high levels of peak muscle activation, independent of visual feedback, but mean activation was higher during TRT. These results suggest that training with no external load might be used as a strategy for stimulating the knee extensors when there is limited access to specialized equipment. Although the clinical applications of no load resistance training are promising, it is important to perform long-term studies to test if these acute results will reflect in muscle morphological and functional changes.

Activity of the Quadratus Lumborum and Trunk Muscles Relates to Pelvic Tilt Angle During Pelvic Tilt Exercises.

Pelvic tilt exercises are used clinically to correct lumbopelvic alignment. The anterior and posterior layers of the quadratus lumborum are important for pelvic motor control in the coronal plane. This study aimed to evaluate whether the anterior and posterior activity is related to the pelvic tilt angle during pelvic tilt exercises. The study design was single-occasion repeated measures in a randomized manner. Twelve healthy men performed the four directions of the pelvic tilt exercises (anterior or posterior pelvic tilt and lateral pelvic elevation on the ipsilateral or contralateral measurement side). The electromyographies of the anterior and posterior were recorded using intramuscular fine-wire electrodes and normalized to isometric peak electromyography. The activity of the anterior and posterior during lateral pelvic elevation on the ipsilateral measurement side (19.0 ± 16.0 percent of maximal voluntary isometric contraction) was significantly higher than that during other directions of the pelvic tilt exercises (P < 0.01). There was a significant positive correlation between the anterior activity and the maximum change angles of pelvic tilt during lateral pelvic elevation on the ipsilateral measurement side (r = 0.674, P = 0.016). The anterior activity was related to a large lateral pelvic elevation angle on the ipsilateral side during pelvic tilt exercises.

High-Density Surface Electromyography Assessment of Pelvic Floor Dysfunction in Women with Interstitial Cystitis/Bladder Pain Syndrome.

Up to 85% of women with interstitial cystitis/bladder pain syndrome have pelvic floor dysfunction and hypertonicity. Current evaluation methodologies lack objective measures of pelvic floor muscle activity. We examined the ability of using intravaginal high-density surface electromyography to quantitatively, objectively and noninvasively map pelvic floor muscle activity and innervation zone locations in patients with interstitial cystitis/bladder pain syndrome. Fifteen women with interstitial cystitis/bladder pain syndrome and 15 controls underwent 2 sessions of digital pelvic examinations and high-density surface electromyography assessments. The root mean squared amplitude of high-density surface electromyography was first calculated, and the resting root mean squared ratio was then calculated by normalizing the resting electromyography root mean squared to the peak electromyography amplitude reached during maximum voluntary contraction. Innervation zone distributions were obtained from decomposed high-density surface electromyography signals. The correlation between the root mean squared ratio and interstitial cystitis/bladder pain syndrome symptom scores and pelvic floor muscle alignment were investigated in patients with interstitial cystitis/bladder pain syndrome and healthy controls. Women with interstitial cystitis/bladder pain syndrome demonstrated significantly increased resting root mean squared ratios compared to controls (0.155±0.048 vs 0.099±0.041, p=0.0019). Significant correlations were found between resting root mean squared ratio and patient reported pain (rs=0.523, p=0.003), interstitial cystitis symptom (rs=0.521, p=0.003) and problem indices (rs=0.60, p <0.001). In addition, women with interstitial cystitis/bladder pain syndrome were more likely to have shortened pelvic floor muscles (80%, 12 vs 13.3%, 2, p <0.01). Women with shortened pelvic floor muscles demonstrated significantly higher resting root mean squared ratio compared to those with normal pelvic floor muscle length (0.155±0.046 vs 0.107±0.040, p=0.0058). Intravaginal high-density surface electromyography offers an objective and quantitative strategy to noninvasively assess pelvic floor muscle dysfunction in women with interstitial cystitis/bladder pain syndrome. Abundant spatiotemporal muscle activity information captured by high-density surface electromyography allows for mapping innervation zone distributions for major pelvic floor muscles.

Cervical spinal V2a neurons pattern respiratory muscle activity and enhance ventilation

Our prior studies suggested that one subset of V2a neurons activates accessory respiratory muscles whereas another subset of V2a neurons actively prevents their activation at rest. However, since these studies altered V2a neuron excitability throughout the spinal cord and brainstem, it was not clear whether the V2a neurons that activate accessory respiratory muscles are located in the same region of the neuraxis as V2a neurons that prevent activation of accessory respiratory muscles at rest. Therefore, we used a Cre‐dependent AAV virus injected into a Chx10Cre/+ mouse to selectively target either the excitatory (Gq)‐ or inhibitory (Gi)‐DREADD receptor to cervical spinal V2a neurons on one side or both sides of the cord in order to alter V2a neuron excitability. Whole breath plethysmography (WBP) and electromyography (EMG) were recorded in conscious mice at rest to measure ventilation and respiratory muscle activity before and after altering V2a neuron excitability. We found that bilaterally increasing the excitability of cervical spinal V2a neurons increases accessory respiratory muscle (scalene) activity, diaphragm EMG peak amplitude, and ventilation. Although V2a neurons project ipsilaterally, increasing their excitability on one side of the cord is able to synchronously activate scalene muscles on both sides of the body. Bilaterally silencing cervical spinal V2a neurons also activates scalene muscle activity, but does not impair diaphragm function. Our results are consistent with the hypothesis that one subset of V2a neurons in the cervical spinal cord activates accessory respiratory muscles whereas another subset of cervical V2a neurons inhibits accessory respiratory muscles at rest.Support or Funding Information1RO1NS112255T32NS5007453University of Cincinnati Dean’s Dissertation Completion Fellowship

Assessing paediatric exercise-induced bronchoconstriction using electromyography.

BackgroundAsthma is one of the most common chronic diseases in childhood, occurring in up to 10% of all children. Exercise-induced bronchoconstriction (EIB) is indicative of uncontrolled asthma and can be assessed using an exercise challenge test (ECT). However, this test requires children to undergo demanding repetitive forced breathing manoeuvres. We aimed to study the electrical activity of the diaphragm using surface electromyography (EMG) as an alternative measure to assess EIB.MethodsForty-two children suspected of EIB performed an ECT wearing a portable EMG amplifier. EIB was defined as a fall in FEV1 of more than 13%. Children performed spirometry before exercise, and at 1, 3 and 6 min after exercise until the nadir FEV1 was attained and after the use of a bronchodilator. EMG measurements were obtained between spirometry measurements.ResultsTwenty out of 42 children were diagnosed with EIB. EMG peak amplitudes measured at the diaphragm increased significantly more in children with EIB; 4.85 μV (1.82–7.84), compared to children without EIB; 0.20 μV (−0.10–0.54), (p<0.001) at the lowest FEV1 post-exercise. Furthermore, the increase in EMG peak amplitude could accurately distinguish between EIB and non-EIB using a cut-off of 1.15 μV (sensitivity 95%, specificity 91%).ConclusionEMG measurements of the diaphragm are strongly related to the FEV1 and can accurately identify EIB. EMG measurements are a less invasive, effort-independent measure to assess EIB and could be an alternative when spirometry is not feasible.

Barbell back squat: how do resistance bands affect muscle activation and knee kinematics?

ObjectivesThis study aimed to determine whether looped resistance bands affect knee kinematics and lower body muscle activation during the barbell back squat.MethodsTwenty-six healthy participants (13 female, 13 male) calculated their...

Comparison of single and multiple joint muscle functions and neural drive of trained athletes and untrained individuals

BACKGROUND: There is insufficient knowledge about the rate of force development (RFD) characteristics over both single and multiple joint movements and the electromechanical delay (EMD) values obtained in athletes and untrained individuals. OBJECTIVE: To compare single and multiple joint functions and the neural drive of trained athletes and untrained individuals. METHODS: Eight trained athletes and 10 untrained individuals voluntarily participated to the study. The neuromuscular performance was assessed during explosive and maximum voluntary isometric contractions during leg press and knee extension related to single and multiple joint. Explosive force and surface electromyography of eight superficial lower limb muscles were measured in five 50-ms time windows from their onset, and normalized to peak force and electromyography activity at maximum voluntary force, respectively. The EMD was determined from explosive voluntary contractions (EVC’s). RESULTS: The results showed that there were significant differences in absolute forces during knee extension maximum voluntary force and EVC’s (p&lt; 0.01) while trained athletes achieved greater relative forces than untrained individuals of EVC at all five time points (p&lt; 0.05). CONCLUSIONS: The differences in explosive performance between trained athletes and untrained individuals in both movements may be explained by different levels of muscle activation within groups, attributed to variation in biarticular muscle function over both activities.

Peak of neuromuscular activation and angle where it occurs during bench press exercise performed with different repetition number and duration in resistance trained individuals

The present study compared neuromuscular activation, measured by surface electromyography (EMG) amplitude [measure by EMG peak (EMGPEAK)] and range of motion (ROM) where EMGPEAK occurred between two training protocols, matched by time under tension, but with a different number and duration of repetitions. Sixteen recreationally trained males performed 2 training protocols with 3 sets, 180 s of rest with 60% of one-repetition maximum(1RM) on the bench press performed in a Smith machine. Protocol A consisted of 6 repetitions with a repetition duration of 6 s and protocol B consisted of 12 repetitions with a repetition duration of 3 s. EMG activity of anterior deltoid, pectoralis major and triceps brachii muscles were recorded. The results showed a general higher EMG amplitude (regardless of the muscle) in protocol B (p = 0.010), and pectoral and triceps brachii consistently presented higher neuromuscular activation than anterior deltoid at both protocols (p = 0.007). Additionally, the ROM where EMGPEAK occurred in triceps brachii was in the middle of the concentric action (~50% of ROM), this occurred in the first half of the same action (~24% of ROM) in the other muscles. In conclusion, protocol B demonstrated an increased EMG amplitude over protocol A, although both protocols responded similarly by achieving the highest EMG amplitude at same ROM among the muscles analysed.

Acute effects of whole-body vibration training on neuromuscular performance and mobility in hypoxia and normoxia in persons with multiple sclerosis: A crossover study

BackgroundWhole-body vibration training (WBVT) has been used in people with relapsing-remitting multiple sclerosis (pwMS), showing improvements in different neuromuscular and mobility variables. However, the acute effects of this training are still unknown. The acute effects of WBVT on neuromuscular performance, mobility and rating of perceived exertion (RPE) were evaluated in 10 pwMS. MethodsMaximal voluntary isometric contraction (MVIC), central activation ratio (CAR), electromyography (EMG) of the vastus lateralis during isometric knee extension, Timed Up and Go Test (TUG), walking speed and RPE were assessed before and immediately after a session of WBVT (twelve 60-s bout of vibration; frequency 35 Hz; amplitude 4 mm; 1-min rest intervals) in both hypoxic and normoxic conditions. ResultsEMG 0–100, 0–200 ms and peak EMG resulted in significant differences (p < 0.05) between normoxic and hypoxic sessions. The EMG activity tended to decrease in all phases after the hypoxic session, indicating possible influence of hypoxia on neuromuscular performance. No changes were found in CAR, MVIC, TUG and walking speed in both conditions. ConclusionBased on our results, as well as those obtained by other studies that have used WBVT with other populations, more studies with a higher sample and lower dose of vibration exposure should be conducted in pwMS.

Squat Lifting Imposes Higher Peak Joint and Muscle Loading Compared to Stoop Lifting

(1) Background: Yearly, more than 40% of the European employees suffer from work-related musculoskeletal disorders. Still, ergonomic guidelines defining optimal lifting techniques to decrease work-related musculoskeletal disorders (WMSDs) has not been unambiguously defined. Therefore, this study investigates if recommended squat lifting imposes lower musculoskeletal loading than stoop lifting while using a complex full body musculoskeletal OpenSim model. (2) Methods: Ten healthy participants lifted two different weights using both lifting techniques. 3D marker trajectories and ground reaction forces were used as input to calculate joint angles, moments and power using a full body musculoskeletal model with articulated lumbar spine. In addition, the muscle activity of nine different muscles was measured to investigate muscle effort when lifting. (3) Results: Peak moments and peak joint power in L5S1 were not different between the squat and the stoop, but higher peak moments and peak power in the hip, knee, elbow and shoulder were found during squat lifting. Moment impulses in L5S1 were higher during stoop lifting. This is reflected in higher peak electromyography (EMG) but lower muscle effort in prior described muscles during the squat. (4) Conclusions: Squat lifting imposes higher peak full body musculoskeletal loading but similar low back loading compared to stoop lifting, as reflected in peak moments, peak power, and peak EMG.

Activation of Scapular and Lumbopelvic Muscles During Core Exercises Executed on a Whole-Body Wobble Board.

Previous studies highlighted that exercises executed on unstable surfaces can yield important benefits to the function of the core musculature in rehabilitation settings, general conditioning settings, and athletic training when properly introduced within a periodized training schedule. No previous study has analyzed core-stability exercises executed in lying, quadruped, plank, and bridge positions on a whole-body wobble board (WWB) specifically designed to accommodate the exerciser's entire body and promote whole-body instability. We have designed a WWB allowed to roll in a plane perpendicular to its longitudinal axis to promote proactive and reactive activation of the core muscles with a transverse or diagonal line of action, which provides trunk and pelvic stability with low spine compression forces. To determine the effect of the use of this newly designed WWB by assessing differences in core-muscle activity during core-stability exercises performed on the ground, in a stable condition, and on the WWB. Controlled laboratory study. Research laboratory. Eighteen participants recruited from fitness centers. The electromyographic (EMG) activity of lumbopelvic and scapular muscles has been recorded during core-stability exercises executed on the WWB (unstable condition) and on ground (stable condition). Mean and peak EMG activity were compared between stable and unstable condition with paired t tests or Wilcoxon signed-rank tests. Overall, exercises performed on the WWB yielded significantly higher EMG activity in the serratus anterior and anterolateral abdominal muscles compared with the same exercises executed on the ground. Conversely, for the bird dog exercise, lower-back muscle activity was significantly higher on the ground. Compared with the ground, core-stability exercises executed on WWB constitute a simple and effective strategy to increase the activity level of the core muscles that control transverse-plane lumbopelvic and trunk stability, avoiding the use of external overload.

Experimental knee pain impairs joint torque and rate of force development in isometric and isokinetic muscle activation.

To investigate the effects of acute experimental knee joint pain on maximum force generation and rate of force development (RFD) of the quadriceps muscle during isometric and dynamic muscle activations. The right knee of 20 healthy people was injected with hypertonic saline to create an acute pain experience. Measurements of maximum knee extensor torque during isometric, concentric, and eccentric contractions were undertaken using a Biodex dynamometer. The RFD was also examined during the isometric contractions. Quadriceps muscle activity was obtained using electromyography (EMG). The outcome measures were obtained at baseline, during pain, and after knee pain had resolved. Maximum joint torque and peak EMG were significantly reduced during pain, but there were no differences across the three types of contraction. The maximum RFD and rate of EMG rise were also reduced during pain, primarily at 50-100ms post-contraction onset. The RFD and EMG rise were largely unaffected at later time periods following contraction onset (150-200ms). Acute joint pain has a similar impact on isometric and isokinetic contractions despite differences in neural control strategies. Joint pain also impairs rapid muscle activation and the RFD. These findings are important for people with musculoskeletal pain as it likely contributes to impairments in joint function in these populations.

Impact of Obesity on Surgeon Ergonomics in Robotic and Straight-Stick Laparoscopic Surgery

Study ObjectiveWork-related musculoskeletal symptoms (WMSs) are reported to be increasing in surgeons performing minimally invasive procedures. Therefore, we investigated the use of inertial measurement units (IMUs) and electromyography (EMG) sensor recorders to record real-time information on the muscle movement/activity required to perform training exercises in simulated in normal and high body mass index (BMI) models. DesignProspective study. SettingUniversity hospital. ParticipantsFour consultant gynecologic oncology surgeons experienced in complex straight-stick (SS) laparoscopic and robotically assisted (RA) surgery. InterventionsThree exercises (hoops onto pegs and wire chase) using SS and RA surgery on 2 abdominal models: normal BMI and high BMI. Measurements and Main ResultsWe measured time to complete exercise and surgeon muscle movement/activity. The time to complete all exercises was significantly lower for RA surgery as compared with SS laparoscopy (p <.05 or better). The movement of the surgeons’ core was significantly greater in high BMI SS laparoscopy compared with normal BMI SS laparoscopy for exercises 1 and 2 (p <.001). Muscle usage, as determined by EMG peak, was significantly higher in normal BMI SS laparoscopy and even higher in high BMI SS laparoscopy but was generally flat for all normal and high BMI RA surgery exercises (p <.05 or better). ConclusionDetailed real-time information can be collected through IMUs/EMG sensors. Our results indicate that RA surgery requires less surgeon movements and muscle activity to complete tasks compared with SS laparoscopy, particularly in a high BMI model. The implications of these results are that RA surgery in high BMI patients may therefore have less physical impact on the surgeon compared with SS laparoscopy and may result in lower WMS rates.

Muscle activation during maximum voluntary contraction and m-wave related in healthy but not in injured conditions: Implications when normalizing electromyography

BackgroundElectromyography signal amplitude is influenced by a variety of factors. Normalization strategies aimed at decreasing signal variability include using peak electromyography signal during a maximum voluntary contraction and peak-to-peak M-wave amplitude. However, whether these normalization methods are comparable has not been investigated in injured populations. This study investigated the relationship between peak signal during maximum voluntary contraction and M-wave amplitude in individuals with a unilateral Achilles tendon rupture. Secondarily, we observed whether the two normalizations strategies would yield similar results when evaluating between limb differences in muscle activity during a jump task. MethodsEleven individuals 1–3 years after a unilateral Achilles tendon rupture were included in this study. Surface electromyography was used on the medial and lateral gastrocnemii bilaterally. Peak maximum voluntary contraction, M-wave amplitude, and electromyography during a jumping task were collected. FindingsA strong relationship was observed between peak maximum voluntary contraction and M-wave amplitude on the uninjured (r = 0.71–0.88, P < 0.05) but not on the ruptured side (r = 0.41–0.44, P > 0.05). The two normalization techniques did not produce different results when comparing the uninjured and ruptured sides. InterpretationThe findings of this study suggest that M-wave normalization yields similar results as peak maximum voluntary contraction-normalized electromyography in uninjured conditions. M-wave normalization may be a useful strategy in an injured population where a maximal muscle contraction is unsafe or impaired.

Muscle Activation in Unilateral Barbell Exercises: Implications for Strength Training and Rehabilitation.

Mausehund, L, Skard, AE, and Krosshaug, T. Muscle activation in unilateral barbell exercises: Implications for strength training and rehabilitation. J Strength Cond Res 33(7S): S85-S94, 2019-The purpose of the present investigation was to assess lower-body muscle activity and hamstrings-to-quadriceps (HQ) activation ratios during performance of the split squat (SS), single-leg squat (SLS), and rear foot elevated split squat (RFESS), while using the same relative load and performing the exercises to muscular failure. Eleven healthy, moderately strength-trained subjects performed a 6-8 repetition maximum set of each exercise while electromyographic (EMG) activity of the vastus lateralis, biceps femoris, gluteus maximus, and gluteus medius was recorded. The results show that there were no significant differences in EMG peak activity of the gluteus maximus and vastus lateralis between any of the exercises. Gluteus medius activation was significantly (p ≤ 0.05) higher during the SLS (81.9% maximum voluntary isometric contraction [MVIC]), compared with the RFESS (54.9% MVIC) and SS (46.2% MVIC). The RFESS elicited higher (p ≤ 0.05) biceps femoris activity (76.1% MVIC) than the SS (62.3% MVIC), as well as higher (p ≤ 0.05) HQ activation ratios (0.83) than the SS (0.69) and SLS (0.63). During the SLS and the SS, HQ activation ratios increased significantly in the course of the repetition maximum set. In conclusion, although absolute loading differs between exercises, similar training stimuli of the gluteus maximus and quadriceps femoris can be expected for all exercises. The SLS is likely to induce the greatest improvements in gluteus medius strength, whereas the RFESS should be preferred if high hamstring coactivation is desired. To improve validity in EMG studies, strength training exercises should be performed close to failure while using the same relative loading.

Effects of Knee Savers on the quadriceps muscle activation across deep knee bending postures

Workers who kneel or squat frequently are at a high risk of developing knee pathologies. Knee Savers® are wedge-shaped pads, worn on the lower calf by baseball catchers that aim to reduce this risk. This study examined how Knee Savers® change the bilateral quadriceps muscle activity during dorsiflexed kneeling, and heels-up and flat-foot squatting. For twenty participants, integrated and peak electromyography (EMG) during descent and ascent phases, mean EMG during a 10-s static phase, and participants’ subjective perception of muscle fatigue were compared between equipment conditions (with (W) and without (WO) Knee Savers®). Knee Savers® did not significantly reduce integrated or peak EMG during transitions into and out of the postures; however, they significantly reduced (p < .03) mean EMG in five of six muscles during the static phase. These findings indicate potential for Knee Savers® to reduce cumulative muscular effort and fatigue in applications where prolonged static kneeling or squatting are required.

Characterizing gait abnormalities in patients with cervical spondylotic myelopathy: a neuromuscular analysis

Background ContextGait impairment is a hallmark of cervical spondylotic myelopathy (CSM). It has been shown to affect quality of life but has not been well defined. Further electromyographic (EMG) characterization of the gait cycle may help elucidate the true neuromuscular pathology with implications on prognosis and rehabilitation techniques. PurposeThis study compares neuromuscular activity in patients with CSM to that of healthy age-matched controls. Study DesignNonrandomized, prospective, concurrent control cohort study. MethodsNeuromuscular activity was measured in 40 patients with symptomatic CSM during a series of over-ground gait trials at a self-selected speed before surgical intervention. External oblique, multifidus, erector spinae, rectus femoris, semitendinosus, tibialis anterior, medial gastrocnemius, and medial deltoid were assessed. Identical measurements were taken in 25 healthy control patients. Differences in time of muscle onset, peak EMG, time to peak EMG, and integrated electromyography (iEMG) were assessed using one-way ANOVA. ResultsThere were no significant differences between patients with CSM and healthy controls with respect to time of muscle contraction onset. Peak EMG muscle activity was significantly higher in the medial deltoid of patients with CSM (39.3% vs. 23.3% sMVC, p=.042), but no other differences were seen in the remaining muscles tested. They also demonstrated significantly longer time to peak EMG muscle activity compared with controls in 5 of the 8 muscles tested, including the multifidus (20.2 vs. 16.8 ms, p=.050), erector spinae (18.2 vs. 8.9 ms, p<.001), semitendinosis (26.3 vs. 22.4 ms, p=.037), tibialis anterior (14.7 vs. 11.0 ms, p=.050), and medial deltoid (24.2 vs. 9.2 ms, p<.001). Compared with controls, patients with CSM demonstrated significantly higher iEMG activity in the semitendinosis (586.5% vs. 272.5 sMVC, p=.047) and medial deltoid (87.62% vs. 22.5% sMVC, p=.008). ConclusionsThe onset of muscle activity is not delayed in CSM patients, but many key muscles take longer to fully contract. This produces a situation in which patients with CSM are unable to fully fire their muscles with sufficient speed to maintain a normal gait. The core and lower extremity muscles do not contract with increased peak amplitude in response, but the deltoid and hamstring muscles are more active, suggesting compensatory activity as patients attempt to maintain balance. The end result is less efficient ambulation. These findings provide a more nuanced understanding of gait in individuals suffering from CSM and may have implications on rehabilitation protocols.