Differences In Electromyographic Activity Research Articles

Influence of temperature on twitch potentiation following submaximal voluntary contractions in human plantar flexor muscles.

This study aimed to clarify the influence of temperature on post-activation twitch potentiation, a possible indicator of fast-twitch fiber activation during a preceding voluntary contraction. Ten healthy males immersed their left lower leg in water of different temperatures (cold: 0°C, neutral: 32-35°C, hot: ~43°C) for 20 min each. In each temperature condition, they performed submaximal (10%-50% of maximal voluntary contraction torque measured before water immersion) and maximal plantar flexions. Immediately after each voluntary contraction, twitch contractions were evoked with supramaximal stimulation of the posterior tibial nerve. The magnitude of twitch potentiation, defined as a percent increase in twitch torque following a voluntary contraction, increased with the intensity of the preceding voluntary contraction. The magnitude of twitch potentiation after the maximal voluntary contraction was smaller in Cold than in the other temperature conditions. However, temperature had no influence on the relative magnitude of twitch potentiation following the submaximal contractions. In addition, there was no difference in electromyographic activity between the gastrocnemius and soleus muscles in any temperature conditions. Collectively, the temperature dependence was not observed when using twitch potentiation or electromyographic amplitude as an indicator of fast-twitch fiber activation during brief submaximal voluntary contractions.

The Difference in Electromyographic Activity While Wearing a Medical Mask in Women with and without Temporomandibular Disorders

Wearing a medical mask influences resting activity of the temporalis anterior and masseter muscles in healthy young women. However, no studies link medical mask-wearing with masticatory muscle activity in patients with temporomandibular disorders (TMDs). Therefore, this study aims to compare electromyographic patterns while wearing a medical mask between women with and without temporomandibular disorders. Based on the Research Diagnostic Criteria for Temporomandibular Disorders, 115 adult women qualified for the study. Participants were divided into the following two groups: diagnosed TMDs (n = 55; mean age: 23.5 ± 2.3 years) and healthy women (n = 60; mean age: 23.7 ± 2.6 years). Examinations of the resting and functional electromyographic activity of the temporalis anterior (TA), superficial masseter (MM), anterior bellies of the digastric muscle (DA), and the middle part of the sternocleidomastoid muscle (SCM) were carried out using the BioEMG III™. Both groups showed statistically significant decreases in resting masticatory muscle activity during medical mask examination compared to no mask measurement. The significant differences in no mask measurement between both groups were noted regarding resting masticatory activity, clenching in the intercuspal position, and clenching on dental cotton rollers. During medical mask examination, women with TMDs showed differences in resting masticatory activity and clenching on dental cotton rollers compared to the healthy group. In all analyzed variables, both groups showed similar electromyographic patterns in the maximum mouth opening measurement during medical mask and no mask examination. A medical mask influences the resting bioelectric activity of the masticatory muscles in women with temporomandibular disorders and healthy women. We observed differences and some similarities in resting and functional electromyographic patterns within masticatory and neck muscles in both groups during medical mask and no mask examination.

Side-To-Side Difference in Electromyographic Activity of Abdominal Muscles during Asymmetric Exercises.

A side-to-side difference in the muscle size of the rectus abdominis has been suggested to increase the strain injury risk. Attenuating the difference in size of the rectus abdominis may decrease the injury risk. To explore ways to highly activate one side of the rectus abdominis, we aimed to clarify the activity levels of both sides of the muscle during asymmetric abdominal exercises. Fifteen male sprinters performed the following five asymmetric exercises for the right and left sides: (i) sit-up twist, (ii) oblique leg raise, (iii) side bridge, (iv) side bridge roll out with the elbow, and (v) side bridge roll out with the foot. Side bridge roll out with the elbow and that with the foot were performed using a wheeled platform. During the exercises, electromyographic signals were recorded bilaterally from the upper, central, and lower portions of the rectus abdominis. We calculated the root mean square of electromyograms during the concentric and eccentric phases of the exercises and normalized to that during maximal voluntary contractions. In all portions of the rectus abdominis, the root mean squares of electromyograms were significantly higher in the moving side than in the non-moving side during the concentric and eccentric phases of the side bridge, the side bridge roll out with the elbow and that with the foot (all p < 0.01), but not in sit-up twist or oblique leg raise. The root mean squares of electromyograms of all portions of the rectus abdominis in the moving side were significantly higher in the side bridge roll out with the elbow and that with the foot than in the side bridge during both phases (all p < 0.01). The results suggest that the application of the wheeled platform to side bridge is useful to highly activate one side of the rectus abdominis.

Sex differences in masticatory muscle activity in healthy young adults

Abstract Introduction. Several studies analyzed the gender differences in masticatory muscle activity. Previous scientific reports indicate the predominance of the masseter muscle activity in male subjects and the predominance of the temporalis anterior in women. However, there is a lack of studies analyzing the differences in the activity of the mandibular abduction muscles between men and women. Aim. The presented study evaluated the sex differences in activity within temporalis anterior, masseter, and digastric muscle in healthy young adults. Material and methods. Thirty-six healthy young adults aged 20 to 29 years (mean 22±2.6 years) were qualified for the presented study. The subjects were divided into two equal groups (n=18) in terms of gender. The masticatory muscle activity was recorded within the temporalis anterior (TA), the superficial masseter muscle (MM), and the anterior bellies of the digastric muscle (DA). Electromyographic activity was recorded in three conditions: at rest, during maximum voluntary clenching at the intercuspal position, and during maximum voluntary clenching with cotton rolls between teeth. Results. Significant differences in electromyographic activity between the male and female group were observed within resting activity for the TA-R (Women: 1.98 µV vs. Men: 1.26 µV; p=0.000), TA-L (Women: 2.13 µV vs. Men: 1.33 µV; p=0.000), DA-R (Women: 2.17 µV vs. Men: 1.29 µV; p=0.001), DA-L (Women: 2.13 µV vs. Men: 1.37 µV; p=0.005). Moreover, significant difference in resting activity index was observed within left side (Women: -9.89 % vs. Men: 10.39%; p=0.037), and within right side during clenching with cotton rolls between teeth (Women: 9.83% vs. Men: 25.59%; p=0.016). Conclusions. Women represent higher resting sEMG activity within the temporalis anterior and digastric muscles than men. Electromyographic patterns may be influenced by gender at rest and during clenching tasks.

Electromyographic Analysis of Exercises on a Gymnastic Horse and a Walking Horse: A Pilot Study

In studies testing the effect of hippotherapy on the human body, no one has yet compared the involvement of the same specific muscles in exercises on a gymnastic (pommel) horse vs. a walking horse. To improve the correct riding seat and to compare the differences in electromyographic activity, we conducted an experimental study to measure the activity of selected muscles on a set of probands of both sexes during three exercises on a gymnastic horse vs. a walking horse. We measured the activity of eight selected muscles, expressed as the percentage value of the maximal voluntary contraction. Maximal voluntary contraction of each muscle was electromyographically measured using Janda’s strength muscle test. These values were used as a standard for values obtained from exercising on a gymnastic horse and a walking horse. The effect of the studied factors was tested by analysis of variance. The muscle activity was statistically significantly affected by the studied factors. It was higher when riding a living horse than a gymnastic horse and in females compared to males. Although the exercises on a gymnastic horse generated lower muscle activity than those on a walking horse, there was a variation among individual muscles that justified further study.

Coordinate activity of the quadratus lumborum posterior layer, lumbar multifidus, erector spinae, and gluteus medius during single-leg forward landing

This study aimed to clarify the differences in electromyographic activity between the quadratus lumborum anterior (QL-a) and posterior layers (QL-p), and the relationship among trunk muscles and gluteus medius (GMed) activities during forward landing. Thirteen healthy men performed double-leg and single-leg (ipsilateral or contralateral sides as the electromyography measurement of trunk muscles) forward landings from a 30 cm-height-box. The onset of electromyographic activity in pre-landing and the electromyographic amplitude of the unilateral QL-a, QL-p, abdominal muscles, lumbar multifidus (LMF), erector spinae (LES), and bilateral GMed were recorded. Two-way ANOVA was used to compare the onset of electromyographic activity (3 landing leg conditions × 10 muscles) and electromyographic amplitude among (3 landing leg conditions × 2 phases). The onset of QL-p was significantly earlier in contralateral-leg landing than in the double-leg and ipsilateral-leg landings. The onset of LMF and LES was significantly earlier than that of the abdominal muscles in contralateral-leg landing. QL-p activity and GMed activity on the contralateral leg side in the pre-landing were significantly higher in contralateral-leg landing than in the other leg landings. To prepare for pelvic and trunk movements after ground contact, LMF, LES, QL-p on non-support leg side, and GMed on support leg side showed early or high feedforward activation before ground contact during single-leg forward landing.

Difference in electromyographic activity between the trapezius muscle and other neck accessory muscles under an increase in inspiratory resistive loading in the supine position

The activity of the trapezius muscle is reportedly higher than that of other neck accessory muscles under a condition of increased inspiratory pressure in the standing position. The present study aimed to compare the activity of the trapezius muscle with those of the scalene and sternocleidomastoid muscles under a condition of increased inspiratory pressure in the supine position. This study included 40 subjects, and the muscle activity was measured using surface electromyography. Regarding the results, there was a significant difference in the muscle activity between the trapezius muscle and the scalene and sternocleidomastoid muscles (p = 0.003) in both men and women. Post-hoc analysis showed significant differences between trapezius and the other muscles. Moreover, there was no difference between the scalene and sternocleidomastoid muscles (p = 0.596). The increase in the change in electromyography activity of the muscle is greater in the trapezius muscle than in other muscles when the level of inspiratory pressure increases in the supine position.

Differences in electromyographic activity of biceps brachii and brachioradialis while performing three variants of curl.

BackgroundDumbbell curl (DC) and barbell curl in its two variants, straight (BC) or undulated bar (EZ) are typical exercises to train the elbow flexors. The aim of the study was to verify if the execution of these three variants could induce a selective electromyographic (EMG) activity of the biceps brachii (BB) and brachioradialis (BR).MethodsTwelve participants performed one set of ten repetitions at 65% of their 1-RM for each variant of curl. Pre-gelled electrodes were applied with an inter-electrode distance of 24 mm on BB and BR. An electrical goniometer was synchronously recorded with EMG signals to determine the concentric and eccentric phases of each variant of curl.ResultsWe detected higher activation profile of both BB (P < 0.05) and BR (P < 0.01) during the EZ compared to the DC. Higher levels of activation was found during the concentric phase for only the BR performed with an EZ compared to DC (P < 0.001) and performing BC compared to DC (P < 0.05). The eccentric phase showed a higher activation of the BB muscle in EZ compared to DC (P < 0.01) and in BC compared to DC (P < 0.05). The BR muscle showed a higher activation performing EZ compared to DC (P < 0.01).DiscussionThe EZ variant may be preferred over the DC variant as it enhances BB and BR EMG activity during the whole range of motion and only in the eccentric phase. The small difference between BC and EZ variants of the BB and BR EMG activity makes the choice between these two exercises a matter of subjective comfort.

Volumetric and Fatty Infiltration Imbalance of Deep Paravertebral Muscles in Adolescent Idiopathic Scoliosis.

BackgroundSeveral studies have described the differences in electromyographic activity and histological changes of paravertebral muscles in patients with adolescent idiopathic scoliosis (AIS). However, there is little knowledge about the muscle volumetric and fatty infiltration imbalance of patients with AIS.Material/MethodsThirty-four patients with AIS were evaluated with standardized anteroposterior (AP) and lateral standing films for the location and direction of the apex of scoliosis, coronal Cobb angle, apex vertebra translation, and thoracic kyphosis; and with magnetic resonance imaging (MRI) scan of the spine at the level of T4–L1. The muscle volume and fatty infiltration rate of bilateral deep paravertebral muscles at the level of upper end, apex, and lower end vertebra were measured.ResultsAll patients had major thoracic curve with apex of curves on the right side. The muscle volume on the convex side was larger relative to the concave side at the three levels, while the fatty infiltration rate was significantly higher on the concave side. The difference index of the muscle volume was significantly larger at the apex vertebra level than at the upper end vertebra level (p=0.002) or lower end vertebra level (p<0.001). The difference index of muscle volume correlated with apex vertebra translation (r=−0.749, p=0.032), and the difference index of fatty involution correlated with apex vertebra translation (r=0.727, p=0.041) and Cobb angle (r=0.866, p=0.005).ConclusionsOur findings demonstrated significant imbalance of muscle volume and fatty infiltration in deep paravertebral muscles of AIS patients. Moreover, these changes affected different vertebra levels, with the most imbalance of muscle volume at the apex vertebra. We interpreted this as morphological changes corresponding with known altered muscle function of AIS.

The Most Effective Number of Elastic Taping Applications on the Muscle Activity and Maximum Peak of the Wrist Extensor Muscle in Patients with Stroke

Objective: The aim of this study is to evaluate the differences in electromyographic activities of upper extremity muscle between repeated taping and to compare the effects of each taping method in stroke patients. Background: Taping studies for functional improvement and pain relief of the UE have been conducted using various methods. Despite being an important factor when you treatment to a patient in a clinical attachment numbers situation quantitative research is that there is not at all to the taping at the time of application. Method: Twenty patients volunteered in this study and were tested under four taping conditions as follows, in random order: (1) no taping, (2) taping applied once, (3) taping applied twice, and (4) taping applied thrice. The muscle activity and maximum peak of the extensor carpi radialis muscle in electromyographic activities were measured, respectively. Results: The muscle activity and maximum peak of the extensor carpi radialis muscle showed significant differences among the four conditions (p Conclusion: These findings demonstrate that repeated taping up to two times may be useful in improving the muscle activity and maximum peak of the extensor muscle. Application: This study provides useful information to future researchers regarding the effects of repeated taping applications on muscle activity and maximum peak of the muscles of the human body.

The Effect of Hand Position Changes on Electromyographic Activity of Shoulder Stabilizers during Push-up Plus Exercise on Stable and Unstable Surfaces

[Purpose] The purpose of this study was to determine the effect of hand position changes on electromyographic activity of shoulder stabilizers during push-up plus exercise (PUPE) performed on both stable and unstable surfaces. [Subjects] This study was performed on a cohort of 20 normal adults divided into an unstable surface group (USG) (n=10) and a stable surface group (SSG) (n=10). [Methods] A sling device was used to provide an unstable surface, and a push-up bar was used to provide a stable surface. PUPEs were performed with hands in various positions: the neutral position (NP), the internal rotation position (IRP), or the external rotation position (ERP). Electromyography was used to determine and analyze the electromyographic activity of the upper trapezius muscle (UT), the lower trapezius muscle (LT), the serratus anterior muscle (SA), and the pectoralis major muscle (PM). [Results] Comparison of the results within the USG and SSG showed significant differences depending on the hand position used during the exercise. Comparison between the USG and SSG showed that the ERP hand posture resulted in significant differences in electromyographic activity of the SA in the USG. [Conclusion] The electromyographic activity of the SA indicated that performing PUPEs using the ERP on an unstable surface provided more effective intervention for shoulder stabilization than ERP on a stable surface.

Kinesio Taping® does not alter neuromuscular performance of femoral quadriceps or lower limb function in healthy subjects: Randomized, blind, controlled, clinical trial

The aim of this study was to analyze the immediate effects of applying Kinesio Taping® (KT) on the neuromuscular performance of femoral quadriceps, postural balance and lower limb function in healthy subjects. This is a randomized, blind, controlled, clinical trial, where sixty female volunteers (age: 23.3 ± 2.5 years; BMI: 22.2 ± 2.1 kg/m2) were randomly assigned to three groups of 20 subjects each: control (10 min at rest); nonelastic adhesive tape (application over the rectus femoris, vastus lateralis and vastus medialis muscles); and KT (KT application over the same muscles). All individuals were assessed for single and triple hops, postural balance (by baropodometry), peak concentric and eccentric torque and electromyographic activity of vastus lateralis, before and after interventions. No significant differences in electromyographic activity of the VL or concentric and eccentric knee peak torque were recorded, between groups and initial and final assessment in any of the three groups. We also observed no significant alteration in single and triple-hop distance and one-footed static balance between the three groups. Application of KT to RF, VL and VM muscles did not significantly change lower limb function, postural balance, knee extensor peak torque or electromyographic activity of VL muscle in healthy women.

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

Most patients with temporomandibular disorders (TMD) have been shown to have cervical spine dysfunction. However, this cervical dysfunction has been evaluated only qualitatively through a general clinical examination of the cervical spine. The purpose of this study was to determine whether patients with TMD had increased activity of the superficial cervical muscles when performing the craniocervical flexion test (CCFT) compared with a control group of individuals who were healthy. A cross-sectional study was conducted. One hundred fifty individuals participated in this study: 47 were healthy, 54 had myogenous TMD, and 49 had mixed TMD. All participants performed the CCFT. Data for electromyographic activity of the sternocleidomastoid (SCM) and anterior scalene (AS) muscles were collected during the CCFT for all participants. A 3-way mixed-design analysis of variance for repeated measures was used to evaluate the differences in EMG activity for selected muscles while performing the CCFT under 5 incremental levels. Effect size values were calculated to evaluate the clinical relevance of the results. Although there were no statistically significant differences in electromyographic activity in the SCM or AS muscles during the CCFT in patients with mixed and myogenous TMD compared with the control group, those with TMD tended to have increased activity of the superficial cervical muscles. The results obtained in this research are applicable for the group of individuals who participated in this study under the protocols used. They could potentially be applied to people with TMD having characteristics similar to those of the participants of this study. This information may give clinicians insight into the importance of evaluation and possible treatment of the deep neck flexors in patients with TMD. However, future research should test the effectiveness of this type of program through a randomized controlled trial in people with TMD in order to determine the real value of treating this type of impairment in this population.

A Crossover Study on the Effect of Cervical Mobilization on Motor Function and Pressure Pain Threshold in Pain-Free Individuals

Objective Cervical mobilization has been shown to elicit effects on pain perception, autonomic function, and motor function in subjects who experience musculoskeletal pain. The improvement in motor function may be a direct effect of the treatment or secondary to a hypoalgesic effect. This study tested whether it is possible to alter motor function following joint mobilization in situations where motor performance is not impaired by pain. Methods Twenty-four asymptomatic subjects participated in this double-blind, controlled, within-subjects crossover study. Pressure pain thresholds and electromyographic activity of the superficial neck flexor muscles were compared with repeated-measures analysis of variance between a posteroanterior cervical mobilization, manual contact, and noncontact condition. Results The results indicate no significant change in the pressure pain threshold ( P =.846) after posteroanterior cervical mobilization. There was no significant difference in superficial neck flexor muscle activity during the craniocervical flexion test ( P =.713). Post hoc power analysis demonstrated the ability to detect a 15% difference in electromyographic activity with 70% power. Conclusion The improvement in motor function demonstrated in previous studies was not replicated, suggesting that either it is only possible to produce an effect when motor function is impaired or the change in motor function is secondary to the pain inhibitory effect of the treatment.

The Influence of Bar Diameter on Neuromuscular Strength and Activation: Inferences from an Isometric Unilateral Bench Press

The purpose of this study was to examine the influence of two different bar diameters on neuromuscular activation and strength. The bar diameters used reflected a standard Olympic bar (28 mm (1.1 inch); THIN) and a larger fat bar (51 mm [2 inch]; THICK). Eighteen healthy men (age 25.0 +/- 1 years) were assessed for their maximal voluntary contraction (MVC) during a unilateral isometric bench press exercise with the 2 bar types at 2 different joint angles (angle 1 and angle 2; elbow joint at approximately 45 and 90 degrees , respectively). Additionally, on a separate day, subjects performed three 10-second isometric repetitions at an intensity of 80% MVC using the 2 different bars at angle 1 and angle 2. Electromyographic recordings were collected in the pectoralis major and the muscles of the forearm flexor region at a sampling rate of 1000 Hz during the second day of testing. Analysis of variance was used to examine differences in MVC between bars and also examine between bar differences in electromyographic activity for each muscle group at each joint angle. A significance level of 0.05 was used for all tests. MVC was not different between bar types, although there was a main effect of joint angle on MVC such that it was greater at angle 2. There was a main effect of bar at both angles for the forearm muscles and at angle 1 for the pectoralis such that electromyographic activity was greater with THIN. Our data do not support the hypothesis that bar diameter influences performance during an isometric bench press exercise. However, higher electromyographic activity with THIN suggests greater neuromuscular activation with a standard Olympic bar as opposed to a larger diameter "fat" bar. Although our data do not support the use of a fat bar for increasing neuromuscular activation, these findings should be confirmed in other resistance training exercises.

Agonist and antagonist muscle activation during maximal and submaximal isokinetic fatigue tests of the knee extensors

The purpose of this study was to examine the differences in electromyographic activity of agonist and antagonist knee musculature between a maximal and a submaximal isokinetic fatigue protocol. Fourteen healthy males (age: 24.3 ± 2.5 years) performed 25 maximal (MIFP) and 60 submaximal (SIFP) isokinetic concentric efforts of the knee extensors at 60° s −1, across a 90° range of motion. The two protocols were performed a week apart. The EMG activity of vastus medialis (VM), vastus lateralis (VL) and biceps femoris (BF) were recorded using surface electrodes. The peak torque (PT) and average EMG (aEMG) were expressed as percentages of pre-fatigue maximal value. One-way analysis of variance indicated a significant ( p < 0.05) decline of PT during the maximal (45.7%) and submaximal (46.8%) protocols. During the maximal test, the VM and VL aEMG initially increased and then decreased. In contrast, VM and VL aEMG continuously increased during submaximal testing ( p < 0.05). The antagonist (BF) aEMG remained constant during maximal test but it increased significantly and then declined during the submaximal testing. The above results indicate that agonist and antagonist activity depends on the intensity of the selected isokinetic fatigue test.

Effect of an unstable shoe construction on lower extremity gait characteristics

To compare kinematics, kinetics and muscle activity during standing and walking for healthy subjects using an unstable test shoe (Masai Barefoot Technology, MBT) and a stable control shoe. Eight subjects volunteered for this study. During quiet standing, center of pressure excursion and muscle activity were determined. During walking, lower extremity kinematics, kinetics, and muscle electromyographic (EMG) signals were determined. Data were collected for the two shoe conditions after a 2week accommodation period. Statistics included repeated measures ANOVAs (alpha = 0.05) and post hoc tests where appropriate. During quiet standing, the center of pressure excursion was significantly and substantially greater in the unstable compared to the control shoe. Electromyographic intensity increased in the unstable test shoe for all tested muscles, but only significantly for the tibialis anterior. During locomotion, kinematics were similar in the two shoe conditions except for the initial plantar-dorsiflexion, which showed a significant more dorsiflexed position during the first half of stance in the unstable test shoe compared to the stable control shoe. The angular impulses did not show any significant differences between the two shoe conditions for all three joints but some trends towards a reduction for the knee and hip joint. There were no significant differences in electromyographic activities between the control and the unstable shoe. However, several muscles showed some trends. The unstable shoe produced changes and trends in kinematic, kinetic and electromyographic characteristics that seemed to be advantageous for the locomotor system. Further studies should investigate muscle strength, dynamic stability, pain reduction for arthritic knees and injury prevention for high performance athletes when using the unstable shoes.

Electromyographic activity of the trunk extensor muscles: Effect of varying hip position and lumbar posture during Roman chair exercise

Mayer JM, Verna JL, Manini TM, Mooney V, Graves JE. Electromyographic activity of the trunk extensor muscles: effect of varying hip position and lumbar posture during Roman chair exercise. Arch Phys Med Rehabil 2002;83:1543-6. Objective: To evaluate the effect of hip position and lumbar posture on the surface electromyographic activity of the trunk extensors during Roman chair exercise. Design: Descriptive, repeated measures. Setting: University-based musculoskeletal research laboratory. Participants: Twelve healthy volunteers (7 men, 5 women; age range, 18–35y) without a history of low back pain were recruited from a university setting. Interventions: Not applicable. Main Outcome Measures: Surface electromyographic activity was recorded from the lumbar extensor, gluteal, and hamstring musculature during dynamic Roman chair exercise. For each muscle group, electromyographic activity (mV/rep) was compared among exercises with internal hip rotation and external hip rotation and among exercises by using a typical lumbar posture (nonbiphasic) and a posture that accentuated lumbar lordosis (biphasic). Results: For the lumbar extensors, electromyographic activity during exercise was 18% greater with internal hip rotation than external hip rotation (P≤.05) and was 25% greater with a biphasic posture than with a nonbiphasic posture (P≤.05). For the gluteals and hamstrings, there was no difference in electromyographic activity between internal and external hip rotation or between biphasic and nonbiphasic postures (P>.05). Conclusion: The level of recruitment of the lumbar extensors can be modified during Roman chair exercise by altering hip position and lumbar posture. Clinicians can use these data to develop progressive exercise protocols for the lumbar extensors with a variety of resistance levels without the need for complex equipment. © 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Electromyographic Comparison of the Développé Devant at Barre and Centre

This investigation compared the electromyographic (EMC) activity of selected muscle groups of skilled dancers executing the développé devant at barre and in centre. A four-channel Nicolet-Viking Biomedical electrograph system was used to assess muscular activity. Surface electrodes were placed over four muscles: quadriceps femoris, hamstrings, tibialis anterior, and abductor hallucis. The participants performed five trials of the développé devant at barre and centre in randomized order. The dancers performed the six phases of the développé devant (coupé, passé, attitude, full extension, tendu, closure to fifth position) in time with a metronome set in three-quarter time at 144 beats per minute. EMC amplitude was recorded at each of the six time phases (1200, 2400, 3600, 4800, 6000, and 7200 msec, respectively). The EMC values (mV) of the raw amplitude of each phase of the développé devant for each subject were “standardized” by dividing by their respective maximum voluntary contraction (MVC). A four-way ANOVA was used to assess the effects and interactions of subjects, trials, phases, and “treatment” (barre versus centre). Results indicated no significant difference (p &lt; 0.05) between barre and centre for either the quadriceps femoris or hamstring muscle of the gesture leg. The main effect of phase was significant (p &lt; 0.05). There was a significant difference in EMC activity (p &lt; 0.05) between barre and centre for the tibialis anterior and abductor hallucis of the standing leg across phases. Post-hoc analysis indicated that EMC activity of the tibialis anterior and abductor hallucis muscles was significantly greater at centre compared to barre during all phases of the développé devant. It was concluded that the training at barre is an acceptable way of preparing the muscles of the gesture leg, but not the standing leg, for the demands of centre.

Differences in electromyographic activity in the multifidus muscle and the iliocostalis lumborum between healthy subjects and patients with sub-acute and chronic low back pain.

The present study was carried out to examine possible mechanisms of back muscle dysfunction by assessing a stabilising and a torque-producing back muscle, the multifidus (MF) and the iliocostalis lumborum pars thoracis (ICLT), respectively, in order to identify whether back pain patients showed altered recruitment patterns during different types of exercise. In a group of healthy subjects (n=77) and patients with sub-acute (n=24) and chronic (51) low back pain, the normalised electromyographic (EMG) activity of the MF and the ICLT (as a percentage of maximal voluntary contraction) were analysed during coordination, stabilisation and strength exercises. The results showed that, in comparison with the healthy subjects, the chronic low back pain patients displayed significantly lower (P=0.013) EMG activity of the MF during the coordination exercises, indicating that, over the long term, back pain patients have a reduced capacity to voluntarily recruit the MF in order to obtain a neutral lordosis. In contrast, during the stabilisation exercises, no significant differences between patients and controls were found for the normalised EMG activity of the two muscles. These findings indicated that, during low-load exercises, no insufficiencies in back muscle recruitment were evident in either subacute or chronic back pain patients. During the strength exercises, the normalised activity of both back muscles was significantly lower in chronic low back pain patients (P=0.017 and 0.003 for the MF and ICLT, respectively) than in healthy controls. Pain, pain avoidance and deconditioning may have contributed to these lower levels of EMG activity during intensive back muscle contraction. The possible dysfunction of the MF during coordination exercises and the altered activity of both muscles during strength exercises may be of importance in symptom generation, recurrence or maintenance of low back pain.