Extensor Carpi Radialis Activity Research Articles

Biomechanical risk factors associated with distal upper extremity musculoskeletal disorders in endoscopists performing colonoscopy

Endoscopists experience upper extremity musculoskeletal injuries. The primary aim of this study was to compare distal upper extremity biomechanical risk factors during colonoscopy with established risk thresholds. Secondary aims were to determine which subtasks during colonoscopy are associated with the greatest risk and to evaluate an intervention to reduce risks. Twelve endoscopists performed 2 to 4 colonoscopies while thumb pinch force and forearm muscle loads of extensor carpi radialis (ECR) and flexor digitorum superficialis (FDS) muscles were collected. Peak exertion values were analyzed using amplitude probability distribution functions. An endoscope support device was evaluated during simulated colonoscopy (n= 8). Mean endoscopist age was 42.3 years; 67% were men. Peak thumb pinch force exceeded risk thresholds for pinch force (10 N) and percent of time spent in forceful pinch for all colonoscopy subtasks. Peak ECR and FDS muscle activity exceeded the action limit (10% maximum voluntary contraction [MVC]) in both forearms. Peak left FDS, left ECR, and right ECR activity exceeded the threshold limit value (>30% MVC). Peak left FDS and ECR activity were significantly greater during insertion than during withdrawal (P< .05). Peak right FDS and ECR activity were significantly greater during right colon insertion compared with withdrawal (P< .05). The endoscope support device reduced left ECR muscle activity (P= .02). Thumb pinch forces and time spent in forceful pinch indicate high-risk exposures during colonoscopy. Left wrist extensor muscle activity exceeded established thresholds with the greatest risk occurring during insertion. An endoscope support device reduced loads to the left wrist extensors.

Alterations in forearm muscle activation patterns after scapholunate interosseous ligament injury: A dynamic electromyography study

Study DesignCase control. Purpose of the StudyThis study aimed to investigate the alterations seen in the activation patterns of the forearm muscles and to demonstrate the associated functional outcomes, in patients with scapholunate interosseous ligament (SLIL) injury. MethodsThe study involved 15 patients with SLIL injury (instability group) and 11 healthy participants (control group). Both groups were evaluated with regard to their pain, grip strength, and upper extremity functional level (disabilities of the arm, shoulder and hand and patient-rated wrist evaluation questionnaires), and they also underwent a dynamic electromyography analysis of their forearm muscle activity. The activation patterns of the extensor carpi ulnaris (ECU), extensor carpi radialis (ECR), flexor carpi ulnaris, and flexor carpi radialis muscles during wrist extension and flexion were recorded by means of surface electromyography. ResultsIn the instability group, the pain severity was higher and the functional level was worse than in the control group (P < .05). Furthermore, during wrist extension, the ECR activity was lower and the ECU activity was higher in the instability group than in the control group (P < .05). ConclusionDynamic stabilization of the wrist, flexor carpi ulnaris, and flexor carpi radialis muscles have been shown to play an active role with ECU and ECR. Increased ECU and decreased ECR activation may pose a potential risk in terms of enhancing the scapholunate gap. We, therefore, propose that appropriate preventive neuromuscular exercise strategies implemented as part of a physiotherapy program for patients with SLIL lesions might increase the contribution of the dynamic stability effect of the relevant muscles.

The immediate effect of whole body vibration training on the electromyographic activity of contralateral hand muscles; a randomized controlled trial

Whole Body Vibration (WBV) has been used as a useful adjunct to improve the neuromuscular function of the upper limb. Cross-transfer of strength plays an important role in rehabilitation of unilateral injuries. The present research intended to evaluate the acute effect of low frequency WBV training on cross-transfer of electromyographic activity and hand muscles strength when the measurement was performed on the contralateral limb. This was a randomized crossover trial conducted in a clinical biomechanics laboratory. Twenty-eight healthy participants aging between 20 and 35 years were included who were involved in two sessions with two weeks of rest. The participants were randomly assigned in two groups as follows: 1) active WBV/sham WBV; 2) sham WBV/active WBV. The participants were asked to stand on the vibrating plate and pull its belt in a vibrating mode using their dominant hand. Then, after a two-week rest, they performed the same task in the vibrating mode (35 Hz). Grip strength and electromyography (root mean square) in flexor digitorum profundus (FDP), flexor digitorum superficialis (FDS), extensor carpi radialis (ECR), and extensor carpi ulnaris (ECU) muscles of the contralateral limb were measured before and after exercise in both phases. No significant change was observed in the electrical activity of FDP, FDS, ECR, ECU muscles, and hands' grip strength of the contralateral limb (P > 0.05). WBV (35 Hz) was not able to augment cross-transfer in electromyographic activity and neuromuscular performance of the upper limb. Further studies would help to explore these results for several sessions of WBV on cross-transfer of training.

Forearm muscle activation, ulnar nerve at the elbow and forearm fatigue in overhand sports

ABSTRACT This study examined the morphologic changes of the ulnar nerve in different elbow positions by ultrasonography and the effects of fatigue on forearm muscle control during overhand movements. We enrolled 12 tennis players who performed flat serves and 15 baseball pitchers who performed fastball pitching. The motion capture was conducted with 14 reflective markers attached on anatomic landmarks of the participant for tennis serve and baseball pitching data collection. The distance from the nerve to the medial condyle between the tennis players and baseball pitchers showed significant differences (p = 0.006) as the elbow flexed to 90°. The differences are due to the baseball player’s repetitive pitching motion while such motion does not apply to tennis player. Activity of the extensor carpi radialis (ECR) during the cocking phase in the tennis serves showed significant differences (p = 0.022) between the nonfatigued and fatigued states; the maximal value was observed in the fatigued state. The significant increase in the ECR activity in the fatigued state might be responsible for grasp-and-release activities and maintaining the wrist joint stability when performing overhand movements. Forearm fatigue influenced their overhand motion ability in accurate ball control, although it did not decrease the ball speed.

Kinematic and Electromyographic Analysis of Wheelchair Propulsion on Ramps of Different Slopes for Young Men With Paraplegia

Chow JW, Millikan TA, Carlton LG, Chae W, Lim Y, Morse MI. Kinematic and electromyographic analysis of wheelchair propulsion on ramps of different slopes for young men with paraplegia. Objective To gain insight into the biomechanics of upslope wheelchair stroking by examining the changes in kinematic and electromyographic characteristics of wheelchair propulsion over ramps of different slopes. Design Repeated-measures design. Each subject pushed up a wooden ramp (7.3m long) 3 times at self-selected normal and fast speeds for each of these slopes: 0°, 2°, 4°, 6°, 8°, 10°, and 12°. Setting A biomechanics laboratory. Participants Young men (N=10) with paraplegia. Interventions Not applicable. Main Outcome Measures Electromyographic activity of extensor carpi radialis, triceps brachii, antero-middle and postero-middle deltoids, pectoralis major, and latissimus dorsi, and stroking kinematics. Results Forward lean of the trunk increased as the slope increased. The triceps brachii, antero-middle deltoid, and pectoralis major were more active during the push phase, while the postero-middle deltoid was more active during the recovery phase. Both extensor carpi radialis and latissimus dorsi were active throughout a stroke. Major adjustments in stroking kinematics and significant increases in muscle activity occurred at slopes between 4° and 10°. Conclusion In addition to a decrease in stroking speed, the stroking pattern becomes more compact (decreased push angle and relative recovery time, increased stroke frequency) and the trunk becomes more active with increasing slope.

Assessment of functional recovery in tennis elbow

Objectives: (a) To investigate changes in muscular strength, fatigue and activity in recovered tennis elbow (RTE); (b) to assess the appropriateness of EMG and strength measurements in monitoring functional recovery in tennis elbow (TE). Methods: Study included three age-matched female groups of Control (C) ( n = 8, no history of musculoskeletal problems), TE ( n = 7, local tenderness at the lateral epicondyle and pain with resisted wrist and middle finger extension) and RTE ( n = 6, asymptomatic for at least 6 months, no lateral epicondyle tenderness). Measurements included metacarpophalangeal (MCP), wrist, shoulder and grip isometric strength and EMG measures of muscle fatigue and activity for five forearm muscles (wrist extensors and flexors). Results: Strength was greater ( p < 0.05) for all measurements in C compared to RTE and TE except for MCP extension. Only MCP extension was stronger in RTE than TE. EMG revealed increased activity of extensor carpi radialis (ECR) in RTE, decreased in TE. Conclusions: Despite attenuation of pain, global upper limb weakness in RTE indicated incomplete functional recovery. Increased strength of MCP extension may protect weakened wrist extensors from further injury. Monitoring the ECR activity as well as strength measurements may provide a useful assessment of functional recovery in TE.

Evaluation of Distal Upper Extremity Musculoskeletal Load During Routine Colonoscopy

Background: Physicians who perform endoscopies are at increased risk for developing recurrent thumb, hand, elbow and low back pain. Musculoskeletal disorders of the upper extremities are related to repeated, forceful movements of the hands and arms. As the demand for colonoscopy increases, so will the physical loads on the hands and arms of endoscopists. The risk factors of upper extremity overuse injuries during routine endoscopy, such as applied pinch force and muscle loads, have not been evaluated during routine endoscopy. We performed a pilot study to determine right thumb pinch force and hand and wrist muscle activities during colonoscopy. Methods: Three gastroenterologists were studied while each performed three colonoscopies. Electromyographic (EMG) activity of the right and left forearm extensor carpi radialis (ECR), right and left flexor digitorum superficialis (FDR), and left abductor pollicis longus (APL) was measured with surface electrodes. Summary measures of EMG data were calculated using the amplitude probability distribution function (APDF), which is a method to quantify muscular activity by normalizing it to maximum voluntary contraction (MVC). Prior studies have shown median levels of muscle activity (APDF 50%tile) of >7-20% MVC and low levels of muscle activity (APDF 10%ile) of >2-5% MVC are associated with increased risk of injury. Right thumb pinch force was measured using a thin profile, custom designed pressure sensor. Prior studies have shown peak pinch force levels (APDF 90%tile) of >10N are associated with an increased risk of injury. Results: The mean peak pinch force across the 9 patients (APDF 90) was 8.6N (SD ± 2.1). The highest pinch forces occurred during insertion: APDF 90 = 10.4N in the left colon and APDF 90 = 10.1N in the right colon. The highest muscle activities were observed in the left ECR (APDF 10 = 10% MVC and APDF 50 = 20% MVC). Left ECR activity was greatest during insertion into the left colon (APDF 10 = 9.0%, APDF 50 = 25.1%) and right colon (APDF 10 = 11.4%, APDF 50 = 23.9%). APDF 10 values of the other muscle groups studied did not exceed 5% of MVC, and APDF 50 values did not exceed 20% of MVC. Conclusions: Based on this pilot data, colonoscopy is associated with a borderline risk of musculoskeletal disorders of the upper extremities, specifically right thumb and left wrist extensor injury. Repeated, high thumb pinch forces can lead to DeQuervain's tendinitis and carpal tunnel syndrome. Repeated, high left ECR muscle loads can lead to second and third extensor compartment tenosynovitis at the wrist and epicondylitis. Further study is needed to identify modifiable risk factors and evaluate methods to reduce this risk.

Counter-moment Effects on Active Wrist Extensor Muscles during Maximal Gripping

Studies have shown that the most common muscle associated with tennis elbow (lateral epicondylitits) is the Extensor Carpi Radialis (ECR). However the etiology of tennis elbow is not fully understood. Electromyographic (EMG) data indicates that persons symptomatic with tennis elbow have higher activity in the wrist extensor musculature of which the ECR is a part. Previous research indicates the ECR is a compensating wrist extension counter-moment muscle due to inhibition of the extensor digitorum during gripping. Due to the ECR's counter moment responsibility within the wrist during gripping It is hypothesized that a maximal external counter moment will decreases ECR EMG activity. PURPOSE: To determine if the influence of a maximal external wrist extension counter-moment significantly changes ECR activity during gripping activities. METHODS: The subject pool consisted of 5 males (Age = 25.67 +4.16 years). The skin was prepared and surface electromyography (EMG) electrodes were placed on the ECR of the dominant arm. A reference maximal isometric contraction of the ECR during gripping of a tennis racket handle (racket head removed) was performed (Grip Condition). During the Counter-moment Condition the participants were asked to position the proximal inter-phalangeal j oint against an immovable obj ect. The participants then gripped the modified racket handle, and maximally abducted their shoulder in order to induce an external wrist extension moment (Counter-moment Condition). RESULTS: A significance decrease was noted in ECR activity across the Grip to Counter-moment conditions (Grip = 285.525 mV+ 61.48 mV, Grip & Counter = 114.6275 mV +34.671 mV) (p< 0.01). CONCLUSIONS: The significance of this study will lead to a better understanding of tennis elbow as well as lay the foundation for scientific counter moment devices that will work to decrease pain in symptomatic persons.

Activity patterns of wrist extensor muscles during wrist extensions and deviations

Wrist extensor muscles are prone to certain focal musculoskeletal disorders for which the activation pattern of the extensor carpi radialis (ECR) and ulnaris (ECU) muscles may be important risk factors. Surface and intramuscular EMG of these muscles were recorded during isometric low-force wrist extension in semipronation and pronation as well as for ulnar/radial deviation, and were analyzed using root mean square (RMS) and decomposition methods. Despite shorter ECR length at semipronation, higher amplitudes of intramuscular EMG and of motor unit action potentials (MUAPs) were found in pronation than in semipronation. However, these changes were not detectable in the surface EMG. Higher ECR activity levels were also found during wrist extension compared to ulnar/radial deviation, and differences in the motor unit (MU) properties were found during ulnar deviation compared to radial deviation and extension. Remarkably, the MUAPs of ECR were almost twice as large as those of the ECU. Overall, the ECR muscle did not respond as predicted from biomechanical considerations, and in general activity level was higher than expected. This may partly explain why the tendon of the ECR often is associated with lateral epicondylitis.

Phasic and tonic reflexes evoked in human antagonistic wrist muscles by tendon vibration

The electromyographic reflex responses of the voluntarily contracting wrist flexor and extensor muscles to periods of vibration-evoked enhanced, Ia-dominated afferent discharge from flexor carpi radialis (FCR) were studied in normal human subjects. Three main response phases were characterised, namely, (i) phasic `on' responses elicited at the commencement of stimulation, (ii) tonic response levels occurring during prolonged stimulation and (iii) phasic `off' responses elicited at the termination of stimulation. The phasic `on' reflex responses of FCR and extensor carpi radialis (ECR) comprised, respectively, a peak of autogenetic excitation of group mean latency 18.8 ms and a trough of reciprocal inhibition of group mean latency 38.0 ms. Prolonged (2 s) trains of FCR (agonist) vibration evoked a phase of tonic reflex excitation in FCR whose mean level was significantly increased, by 20%, above pre-stimulus activity and which did not change over the 0.5–2.0 s vibration period. Progressive reduction of the duration (from 2000 ms to 100 ms) of vibration trains demonstrated that phasic disfacilitatory `off' troughs regularly occurred, with a consistent latency (mean 24.2 ms), on withdrawal of each period of enhanced Ia-input. This indicates that the responsible excitatory reflex mechanism was operational for the entire duration of each of the vibration periods tested. The extra latency (on average 5.4 ms) of phasic `off' relative to `on' responses may be attributed to factors (e.g. 5–10 ms duration of unitary muscle action potentials and afterdischarge in reflex pathways) which inevitably delay the appearance of overt disfacilitatory reductions in EMG rather than the involvement of different reflex pathways. Thus, short-latency, possibly monosynaptic, reflex excitation contributed throughout the entire tonic excitatory response. Sustained FCR (antagonist) vibration produced a significant tonic reciprocal inhibitory reflex depression, by 7% pre-stimulus EMG, of ECR activity which remained steady during the 0.5–2.0 s vibration period. The absence of well-defined phasic disinhibitory `off' responses in ECR suggests that the contribution of oligosynaptic reflex inhibitory mechanisms to the tonic suppression of activity occurring during continuing vibration is relatively small.