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PubMed2001

Is the ulnar nerve damaged in 'handball goalie's elbow'?

'Handball goalie's elbow' has been defined as pain in the elbow region due to repetitive forced hyperextensions of the elbow. Goalkeepers are the players most often suffering from hyperextension trauma to the elbow in European team handball. They may complain of radiating pain or numbness in the ulnar aspect of the forearm in addition to local pain in the elbow region. To detect any injury to the ulnar nerve that could explain the symptoms, we performed a neurological and neurophysiological study in goalkeepers with elbow pain. Nine goalkeepers, with a total of 15 'handball goalie's elbow', were included in this study. Neurological examination revealed a probable ulnar nerve lesion in one player. Neurophysiological and electromyographic examinations (10 examinations) were, however, normal in all players. Handball goalkeepers with elbow problems may suffer from symptoms suggestive of ulnar nerve affection, but serious or permanent injury to the ulnar nerve with wasting or paresis is unusual.

Adolescent↗
PubMed2001

Traumatic elbow subluxation in a child: case report.

An 11-year-old boy fell on his outstretched right arm, following which he had pain on the lateral aspect of his right elbow with limitation of range of motion. Roentgenograms showed right elbow subluxation. The elbow was reduced and immobilized in a long arm splint for 5 days. The result was excellent. Elbow subluxation in previous reports was the result of recurrent elbow dislocation with instability. There are no reports of elbow subluxation in patients who did not have underlying recurrent elbow dislocation or elbow instability. This condition is easy to diagnose and has an excellent outcome.

Child↗
PubMed1993

[Simple elbow dislocation. Comparison of long-term results after immobilization and functional treatment].

From 1976 to 1985 the treatment used for simple dislocation of the elbow consisted in closed reduction and immobilization for about 3-4 weeks. Since 1985, simple dislocation of the elbow has been treated with closed reduction and immobilization for fewer than 3 days. A group treated by immobilization (20 patients) and a group that underwent functional treatment (24 patients) were both evaluated with regard to elbow motion, instability, isometric flexor and extensor strength of the forearm, and subjective (patient) judgement of the elbow function. An average of 8 +/- 5 years after the treatment 39 elbows were re-examined. In both groups, results were generally good, 22 patients having no residual symptoms or signs. However, 17 did have symptoms: 6 patients had a slight (loss of extension < 10 degrees, loss of flexion < 10 degrees) and 1 patient a moderate decrease in the range of motion (loss of extension > 10 degrees). Some instability was found in 5 patients and strength was slightly decreased in 9. The subjective judgement on their elbow function was very good in 22 patients. At follow-up, no statistically significant differences were found between the two groups. The retrospective study, however, revealed that immobilization for 3-4 weeks more than doubled the time of after-treatment, the period of disability of the elbow, and the period of physical rehabilitation. Therefore, an accelerated functional treatment is recommended for the treatment of simple elbow dislocation: this is more effective, takes less time and is more economical.

Adult↗
PubMed2002

Shock wave therapy for lateral elbow pain.

BACKGROUND: This review is one in a series of reviews of interventions for lateral elbow pain. Lateral elbow pain, or tennis elbow, is a common condition causing pain in the elbow and forearm and lack of strength and function of the elbow and wrist. Shock wave therapy (ESWT) involves the application of single pulsed acoustic wave. Since the 1990's reports of benefit of ESWT in the treatment of tendon disorders have been appearing in the literature. A systematic review published in the German language appeared in 2000 (Boddeker 2000) OBJECTIVES: To determine the effectiveness and safety of ESWT in the treatment of adults with lateral elbow pain. SEARCH STRATEGY: Comprehensive electronic searches of MEDLINE, CINAHL, EMBASE and SCISEARCH were combined with searches of the Cochrane Clinical Trails Registrar and the Musculoskeletal Review Group's specialist trial database. Identified keywords and authors were searched again in an effort to identify as many trials as possible. SELECTION CRITERIA: Two independent reviewers assessed all identified trials against pre-determined inclusion criteria. Randomised and pseudo randomised trials in all languages were evaluated for inclusion in the review provided they described individuals with lateral elbow pain and were comparing the use of ESWT as a treatment strategy. DATA COLLECTION AND ANALYSIS: For continuous variables means and standard deviations were extracted or imputed to allow the analysis of weighted mean difference. Weighted mean difference using a random effects model was selected when outcomes were measured on standard scales. A fixed effects model was used to interpret results and assess heterogeneity. For binary data numbers of events and total population were analysed and interpreted as relative risk. MAIN RESULTS: Two trials of ESWT versus placebo are included in this review (~~Rompe 1996~~, ~~Haake 2001~~). Both trials included similar study populations consisting of participants with chronic symptoms who had failed other conservative treatment. The frequency of ESWT application and the doses and techniques used were similar in both trials. The first trial demonstrated highly significant differences in favour of ESWT whereas the second trial found no benefits of ESWT over placebo. When the data from the two trials were pooled, the benefits observed in the first trial were no longer statistically significant. The relative risk for treatment failure (defined as Roles-Maudsley score of 4) of ESWT over placebo was 0.40 (95% CI, 0.08 to 1.91) at six weeks and 0.44 (95% CI, 0.09 to 2.17) at one year. After 6 weeks, there was no statistically significant improvement in pain at rest [WMD pain out of 100 = - 11.40 (95% CI, -26.10 to 3.30)], pain with resisted wrist extension [WMD pain out of 100 = -16.20 (95% CI, -47.75 to 15.36)] or pain with resisted middle finger extension [WMD pain out of 100 = -20.51(95% CI, -56.57 to 15.56)]. Results after 12 or 24 weeks were similar. REVIEWER'S CONCLUSIONS: The two trials included in this review yielded conflicting results. Further trials are needed to clarify the value of ESWT for lateral elbow pain.

Adult↗
PubMed2002

Non-steroidal anti-inflammatory drugs (NSAIDs) for treating lateral elbow pain in adults.

BACKGROUND: Lateral elbow pain, or tennis elbow, is a common condition causing pain in the elbow and forearm and lack of strength and function of the elbow and wrist. It is often treated with non-steroidal anti-inflammatory drugs (NSAIDs), either orally or by topical application. OBJECTIVES: To assess effectiveness of NSAIDs (oral or topical) in the treatment of adults with lateral elbow pain with respect to symptom (pain) reduction, improvement in function, grip strength and adverse effects. SEARCH STRATEGY: We searched the Musculoskeletal Review Group's trials register database, the Cochrane Clinical Trials Register (Cochrane Library issue 2, 2001), MEDLINE, CINAHL, EMBASE and SCISEARCH up to June 2001. SELECTION CRITERIA: Randomised and pseudo randomised trials in all languages of NSAIDs (oral or topical) compared to placebo or another intervention, or comparing two NSAIDs (oral or topical) to each other, in adults with lateral elbow pain (tennis elbow). Outcomes of interest were pain, function, disability and quality of life, strength, participant satisfaction with treatment and adverse effect. DATA COLLECTION AND ANALYSIS: Two reviewers independently applied selection criteria and assessed study quality. MAIN RESULTS: Fourteen trials were included in the review. Few trials used intention to treat analysis, and the sample size of most was small. The median follow up was 2 weeks (range 1-12 weeks). There is evidence that topical NSAIDs are significantly more effective than placebo with respect to pain [weighted main difference= -1.88, (95% confidence intervals -2.54 to -1.21)] and participant satisfaction [relative risk 0.39, (95% confidence intervals 0.23 to 0.66)] in the short term, and this finding is robust against the possible bias introduced by the inclusion of unblinded trials and publication bias. The adverse effects reported were minor. Only two included trials assessed the effect of oral NSAID and these were not able to be pooled. There is some evidence for short term benefit with respect to pain and function from oral NSAIDs, but this benefit was not sustained. Significantly more gastrointestinal adverse effects were reported by those taking oral NSAIDs [relative risk = 3.17, (95% confidence intervals 1.35 to 7.41)]. In the short term there may be some advantage in steroid injection over oral NSAID [patient's perception of benefit relative risk = 3.06, (95% confidence intervals 1.55 to 6.06)], but this was not sustained in the longer term. REVIEWER'S CONCLUSIONS: There is some support for the use of topical NSAIDs to relieve lateral elbow pain at least in the short term. There remains insufficient evidence to recommend or discourage the use of oral NSAID, although it appears injection may be more effective than oral NSAID in the short term. A direct comparison between topical and oral NSAID has not been made and so no conclusions can be drawn regarding the best method of administration.

Administration, Oral↗
PubMed1993

Differences in activation patterns in elbow flexor muscles during isometric, concentric and eccentric contractions.

To investigate the relative activation of the synergistic muscles during three different types of muscle contraction, the electromyograms (EMG) of two elbow flexor muscles, the biceps brachii (BB) and the brachioradialis (BR), have been compared. To accomplish this eight healthy human subjects performed the following elbow flexions against the same load--concentric, eccentric and isometric contractions. The isometric contractions were performed at three elbow angles: 10, 45 and 90 degrees (0 degree equal to full extension). The EMG were recorded by bipolar surface electrodes, and the relative activation between the two muscles was evaluated as the quotient of mean EMG activities (BR/BB). For the isotonic elbow flexions, BR/BB were calculated at three angle divisions: 0-30 degrees, 30-60 degrees and 60-90 degrees. Results indicated that the relative activation of the BR during the concentric contractions was higher than that of the eccentric contraction, particularly at the extended elbow angles, i.e. the BR/BB of the concentric contractions for the elbow joint angles ranging from 0-30 degrees and 30-60 degrees were significantly greater (P < 0.05) than those of the eccentric contractions. During the isometric and eccentric contractions, the BR/BB at the flexed joint angles tended to be greater than those at the extended angles. In contrast, there were no angle-dependent BR/BB variations during the concentric elbow flexions. Further, changing patterns in the EMG power spectra due to the type of contraction were different between BB and BR. These results indicated that the activation pattern in the two elbow flexor muscles varied with the muscle contraction pattern.

Adult↗
PubMed2005

Braking of elbow extension in fast overarm throws made by skilled and unskilled subjects.

A previous computer simulation study of overarm throws in 2D showed that reversal of elbow torque by antagonist muscle action late in the throw led to increased wrist flexion velocity and to increased ball speeds. We tested the hypothesis that the skill of making fast overarm throws in 3D involves deceleration (braking) of elbow extension before ball release, and that this is an active mechanism. Skilled and unskilled throwers were instructed to throw baseballs at a fast speed. Arm segment angular positions in 3D at 1,000 Hz were recorded with the search-coil technique (which records angular motions). In skilled throws, but not in unskilled throws, there was a period (mean 17 ms) of rapid elbow extension deceleration before ball release. However, there was relatively little biceps EMG activity associated with the very large magnitude of elbow deceleration. This finding and other work suggests that elbow extension deceleration results in part from interaction torques associated with late-occurring shoulder rotations, and only in part from elbow flexor contraction. During the period when elbow extension was decelerating, the forearm in space was undergoing angular acceleration (because of internal rotation at the shoulder) which would be expected to produce a torque at the wrist in the extensor (not flexor) direction. The results show that elbow extension deceleration occurs before ball release in fast (skilled) 3D throws, and that it does not produce forearm angular deceleration. Whether it produces forearm translational deceleration, which could increase wrist flexion velocity, remains to be determined.

Adult↗
PubMed1998

Independent coactivation of shoulder and elbow muscles.

The aim of this study was to examine the possibility of independent muscle coactivation at the shoulder and elbow. Subjects performed rapid point-to-point movements in a horizontal plane from different initial limb configurations to a single target. EMG activity was measured from flexor and extensor muscles acting at the shoulder (pectoralis clavicular head and posterior deltoid) and elbow (biceps long head and triceps lateral head) and flexor and extensor muscles acting at both joints (biceps short head and triceps long head). Muscle coactivation was assessed by measuring tonic levels of electromyographic (EMG) activity after limb position stabilized following the end of the movements. It was observed that tonic EMG levels following movements to the same target varied as a function of the amplitude of shoulder and elbow motion. Moreover, for the movements tested here, the coactivation of shoulder and elbow muscles was found to be independent - tonic EMG activity of shoulder muscles increased in proportion to shoulder movement, but was unrelated to elbow motion, whereas elbow and double-joint muscle coactivation varied with the amplitude of elbow movement and were not correlated with shoulder motion. In addition, tonic EMG levels were higher for movements in which the shoulder and elbow rotated in the same direction than for those in which the joints rotated in opposite directions. In this respect, muscle coactivation may reflect a simple strategy to compensate for forces introduced by multijoint limb dynamics.

Elbow↗
PubMed2006

Muscle changes in brachial plexus birth injury with elbow flexion contracture: an MRI study.

BACKGROUND: Muscle pathology of the arm and forearm in brachial plexus birth injury (BPBI) with elbow flexion contracture has not been evaluated with MRI. OBJECTIVE: To determine whether limited range of motion of the elbow in BPBI is correlated with specific patterns of muscular pathology. MATERIALS AND METHODS: For 15 BPBI patients, total active motion (TAM) of the elbow (extension-flexion) and the forearm (pronation-supination) were measured. MRI of the elbow joints and musculature allowed assessment of elbow congruency. Fatty infiltration and size reduction of the muscles were graded semiquantitatively. RESULTS: Mean TAM of the elbow was 113 degrees (50 degrees-140 degrees) and that of the forearm 91 degrees (10 degrees-165 degrees). The greater the size reduction of the brachioradialis muscle, the more diminished was elbow TAM. The more extensive the BPBI and muscle pathology of the pronator teres muscle, the more limited was the TAM of the forearm. Pathology of the supinator and brachialis muscles was evident in every patient. CONCLUSION: Extensive BPBI may result in marked limitation of TAM. Elbow flexion contracture seems to be caused mainly by brachialis muscle pathology. Prosupination of the forearm is better preserved when the pronator teres is not severely affected. MRI can reliably show the extent of muscle pathology in BPBI.

Adolescent↗
PubMed1995

Pulled elbow--not the effect of hypermobility of joints.

A detailed description of pulled elbow is missing from standard orthopaedic text books. Recently it has been reported that the prevalence of hypermobility among children with pulled elbow is higher than that in the normal population and that pulled elbow can be considered to be a consequence of joint hypermobility. Two hundred children with pulled elbow comprising 106 girls and 94 boys (age range 3-84 months, mean age 24 months) were treated and evaluated for signs of hypermobility in a prospective study. Hypermobility of joints was noted in 17 (8.5 per cent) of children who had a pulled elbow while in the 71 children in whom there had been more than one episode, the rate of hypermobility was 8.4 per cent. Comparison of these results with a control group of 100 normal children, in whom 10 (10 per cent) exhibited hypermobility, showed no association between joint hypermobility and an increased incidence of pulled elbow. The anatomical construction of the radial head, relative plasticity of the cartilage and the immature annular ligament in young children possibly predisposes them to pulled elbow, the incidence of which is increasing in our modern physically competitive society where children are participating in a wide range of physically demanding sports activities. Pulled elbows can also occur in children with hypermobility of joints, but there is no evidence that the incidence has increased.

Child↗
PubMed1994

Cementless or hybrid total elbow arthroplasty with titanium-alloy implants. A study of interim clinical results and specific complications.

Twenty-six patients (32 elbows) with rheumatoid arthritis had a total elbow arthroplasty with insertion of a cementless prosthesis. The humeral component was made of titanium alloy and it was fixed without cement in all elbows. The patients were followed for an average of 3 years 1 month (range, 2 years 2 months to 4 years 4 months). A good result was seen in 25 elbows, a fair result in 2, and a poor result in 5. The reason for the poor results was a breakage of the humeral component at the junctional portion of its stem. In all five of these elbows a marked resorption of bone mass within the condylar portion of the humeral component was observed on the lateral radiograph. The five elbows with a poor result had a revision operation, and in each of these black staining of the soft tissues within the joint was seen. This tissue metallosis due to wear debris of the titanium alloy was responsible for the osteolysis within the condylar portion. It became clear from this study that even in a non-weight-bearing joint, such as the elbow, titanium alloy may wear and result in tissue metallosis when used as a bearing surface of the implant. However, it was also found that in the majority of the elbows an establishment of the biologic fixation of the porous-coated stem could be achieved by use of this alloy.

Adult↗
PubMed2004

Triceps denervation as a predictor of elbow flexion contractures in C5 and C6 tetraplegia.

OBJECTIVE: To determine whether the existence of elbow flexion contractures in persons with C5 or C6 tetraplegia is related to a lack of residual voluntary triceps function and triceps denervation (ie, lower motoneuron damage). DESIGN: A retrospective study of impairment data from 74 arms to identify the incidence of elbow flexion contractures and the contributing factors toward this deformity. SETTING: Five spinal cord injury (SCI) rehabilitation centers in the United States, 1 in England, and 1 in Australia. PARTICIPANTS: Forty-three subjects with motor complete C5 or C6 traumatic SCI. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Active and passive elbow extension, triceps voluntary muscle strength, and triceps response to electric stimulation. RESULTS: Subjects with weak voluntary triceps had significantly fewer and less severe elbow flexion contractures than those with paralyzed triceps ( P =.024). Subjects with completely denervated triceps (ie, no response to electric stimulation) had significantly more elbow flexion contractures than subjects with even a weak response to electric stimulation ( P =.003). Overall, 51% of the arms could not be passively extended to zero. Forty-six percent of the arms classified as C5 lacked full passive elbow extension, compared with 63% of the arms classified as C6 ( P =.302). CONCLUSIONS: A relationship has been found between elbow flexion contractures and lack of residual voluntary triceps and triceps denervation in subjects with C5 or C6 tetraplegia. There should be a greater awareness of the elbow flexion contractures that may develop as a result of this relationship. A better understanding of this deformity and its characteristics can lead to more effective clinical treatment and prevention strategies.

Adolescent↗
PubMed2005

Ulnar collateral ligament of the elbow.

Recent advances in the diagnosis and treatment of the overhead athlete's elbow has led the medical community to understand that the ulnar collateral ligament (UCL) of the elbow is more commonly injured than originally thought. Injury can result in secondary symptoms and problems in other regions of the elbow. Sports requiring an overhead motion, such as throwing a ball, hitting a ball overhead, or serving a tennis ball, imparts a valgus stress on the elbow that is resisted by the UCL. Throwing sidearm or hitting a forehand in tennis, squash, or racquetball may also impart a valgus stress to the elbow. Repeated or excessive valgus stress places a force on the UCL that may result in injury to the ligament. Injury to the UCL may result in problems in other areas of the elbow, including the ulnar nerve, the flexor-pronator musculotendinous unit, the radiocapitellar joint and the posterior compartment of the elbow, in addition to being a cause of loose bodies within the elbow. This article reviews the anatomy, biomechanics, and pathophysiology of injury to the UCL and injuries to the other structures that result from UCL injury. Also reviewed are patient history, examination techniques, tests that help confirm the diagnosis of UCL injury, and treatment of the injured UCL.

Arthroscopy↗
PubMedDate not supplied

Capitellocondylar total elbow replacement in late-stage rheumatoid arthritis.

Between 1994 and 2000, 51 capitellocondylar elbow replacements were inserted in 41 patients. All patients had late-stage rheumatoid arthritis. The mean age at operation was 56 years (range, 25-78 years). There were 12 men and 29 women. At follow-up, 6 patients had died of unrelated causes with the implant in situ and without radiographic loosening, and 1 patient was lost to follow-up. The remaining 43 elbows in 34 patients were followed up clinically and radiographically at a mean of 6.9 years (range, 26-119 months). Relief of pain was complete in 91% of the surviving elbows, and in 9%, there was only mild pain. Pain-free range of motion at follow-up was significantly improved. Flexion increased a mean of 43 degrees ; extension, 16 degrees ; supination, 24 degrees and pronation, 26 degrees . Of the elbows, 7 underwent revision, 3 because of deep infection, 1 for aseptic loosening, and 3 because of instability. Other complications included 2 maltracking elbows, 2 triceps tendon ruptures, 2 cases of operative olecranon bursitis, and 2 ulnar nerve palsies. One elbow showed radiolucent lines of more than 1 mm in the circumference of the ulnar component; none of the other elbows showed any signs of progressive radiographic loosening. At a mean follow-up of 6.9 years, a functional prosthesis was retained in 82.7% of the elbows, and the mean survival of the implant was 8.6 years (95% CI, 7.8-9.5 years).

Adult↗
PubMed1995

Elbow extension using anterior deltoids and upper pectorals in spinal cord-injured subjects.

OBJECTIVE: Surface electromyography was used to identify muscles active in isometric elbow extension in spinal cord-injured (SCI) patients. DESIGN: Tetraplegic subjects participated in this cohort study aimed at identifying some of the muscles that are active during isometric elbow extension. SETTING: Regional Spinal Cord Injury (SCI) Center. PATIENTS: The patients had to have a C6 motor level on the right side (wrist extensor > or = 3/5) with 0/5 or 1/5 elbow extensor muscle power. Of 32 patients who could be contacted by telephone, 6 eventually were able to make it to the SCI center for testing. MEASUREMENTS: The patients performed a series of isometric elbow extension contractions of 25%, 50%, and 75% of maximum voluntary contraction (MVC) as measured by a force transducer. Surface electromyography (EMG) of the right elbow extensor, anterior deltoid, and upper pectoral muscles was measured using the root mean square (rms) of the amplitude of the motor unit activity as the parameter of muscle activity. Statistical analyses were performed using a repeated analysis of variance (ANOVA) with Tukey post-hoc HSD for each percentage of MVC. RESULTS: For each muscle tested, there was significantly (p < 0.05) greater rms activity for each percentage of MVC except between 50% and 75% MVC of the elbow extensor muscle. However, the elbow extensor muscle had minimal EMG activity when compared with the amplitude of the rms activity of the anterior deltoid and upper pectoral muscles for each percentage of MVC. CONCLUSION: The results of the study suggest that the anterior deltoid and the upper pectoral muscles exert an isometric elbow extension force for C6 quadriplegic patients.

Adult↗
PubMed2000

Total elbow arthroplasty as primary treatment for distal humeral fractures in elderly patients.

Distal humeral fractures are difficult to treat. In the elderly population, the problems are compounded by osteoporosis and gross comminution. Open reduction and internal fixation for such fractures is sometimes difficult and may be associated with poor results. Total elbow arthroplasty has been suggested as a last-ditch effort to salvage functional use for such difficult fractures in the elderly. We followed seven patients (seven elbows) with a mean age of 81.7 years at the time of injury. Open reduction and internal fixation was considered a difficult option for these fractures. They were treated with a total elbow arthroplasty using the semi-constrained Coonrad-Morrey elbow replacement prosthesis. The duration of follow up at present is between 2 and 4 years. At the latest follow up the mean arc of flexion is 20-130 degrees. Six patients have no pain while one complains of mild pain. All elbows are stable. The Mayo elbow performance score for five elbows is excellent and two scored good. All but one patient are satisfied with the result. One patient developed superficial wound infection which resolved after antibiotic therapy. One patient has developed post-operative triceps weakness. There have been no cases of deep infection, ulnar nerve neuritis or component failure. The rarity of this procedure suggests its very narrow spectrum of indication. We feel that the short-term results do suggest an important role for semi-constrained total elbow arthroplasty in managing carefully selected comminuted distal humeral fractures in the elderly, especially those that cannot be treated by conventional open reduction and internal fixation.

Aged↗
PubMed2000

Strategies used to stabilize the elbow joint challenged by inverted pendulum loading.

The stiffness of activated muscles may stabilize a loaded joint by preventing perturbations from causing large displacements and injuring the joint. Here the elbow muscle recruitment patterns were compared with the forearm loaded vertically (a potentially unstable inverted pendulum configuration) and with horizontal loading. Eighteen healthy subjects were studied with the forearm vertical and supinated and the elbow flexed approximately 90 degrees. In the first experiment EMG electrodes recorded activity of biceps, triceps, and brachioradialis muscles for joint torques produced (a) by voluntarily exerting a horizontal force isometrically (b) by voluntarily flexing and extending the elbow while the forearm was loaded vertically with 135N. The relationship between the EMG and the torque generated was quantified by the linear regression slope and zero-torque intercept. In a second experiment a vertical load increasing linearly with time up to 300N was applied. In experiment 1 the EMG-torque relationships for biceps and triceps had an intercept about 10% of maximum voluntary effort greater with the vertical compared to the horizontal force, the inverse was found for Brachioradialis, but the EMG-torque slopes for both agonist and antagonistic muscles were not different. In experiment 2 there were 29 trials with minimal elbow displacement and all the three muscles activated on the order of 11% of maximum activation to stabilize the elbow; 19 trials had small elbow extension and 14 trials small flexion requiring altered muscle forces for equilibrium; 7 trials ended in large unstable displacement or early termination of the test. An analysis indicate that the observed levels of muscle activation would only provide stability if the muscles' short-range stiffness was at the high end of the published range, hence the elbow was marginally stable. The stability analysis also indicated that the small elbow extension increased stability and flexion decreased stability.

Algorithms↗
PubMed2000

Moment distribution among human elbow extensor muscles during isometric and submaximal extension.

To understand better how the central nervous system (CNS) distributes a joint moment among muscles, moment distribution among the three heads of the triceps and the anconeus muscles during isometric elbow extension was quantified in vivo and noninvasively. Electrical stimulation was used to activate an individual muscle selectively at various contraction levels, and the relationship between the peak M-wave amplitude and peak elbow extension moment was established across various contraction levels for each muscle. The relationship was then used to calibrate the corresponding EMG signal and determine moment distribution among the muscles during voluntary isometric elbow extension. Results showed that moment distribution among muscles was not proportional to the muscles' physiological cross-sectional areas (PCSA) and the CNS favored uniarticular muscles for the isometric task performed: the uniarticular lateral and medial heads of the triceps were dominant (contributing approximately 70-90% of the total elbow extension moment) and the anconeus contributed significantly, especially at the lower levels of elbow extension moment (up to approximately 15% of the extension moment). In contrast, the two-joint long head of the triceps contributed significantly less than the uniarticular heads of the triceps. While the absolute contributions of all the muscles increased with the total elbow extension moment, the relative contributions of the muscles may increase or decrease with the elbow extension moment. Cross-validation using fresh data (not used in determining the moment distribution) showed close match between the measured and predicted elbow extension moment except for trials in which fatigue became significant.

Elbow↗