The Role of the Muscle Brachioradialis in Elbow Flexion: An Electromyographic Study

Rupture of the brachioradialis muscle following blunt trauma. A case report

A 50-year old healthy male lost control over the pull string of a milling machine, which strangulated his right elbow and forearm with high velocity. Magnetic resonance imaging of the right upper extremity revealed a substantial tear in the muscle belly of the musculus brachioradialis with multiple small defects in the surrounding musculature of the forearm. The affected arm was immobilized for 1 week with an above the elbow cast. In the following months, guided training and strengthening exercises were performed. The patient could return to his physically demanding work after 10 months and regained full function of his hand and wrist after 18 months. This case report demonstrates that short immobilization followed by extensive and guided strength training has been observed to result in persisting weakness of elbow flexion but good functional outcome for the wrist and hand.

The Effects of the Biceps Brachii and Brachioradialis on Elbow Flexor Muscle Strength and Spasticity in Stroke Patients

Objective

Muscle weakness and spasticity are common consequences of stroke, leading to a decrease in physical activity. The effective implementation of precision rehabilitation requires detailed rehabilitation evaluation. We aimed to analyze the surface electromyography (sEMG) signal features of elbow flexor muscle (biceps brachii and brachioradialis) spasticity in maximum voluntary isometric contraction (MVIC) and fast passive extension (FPE) in stroke patients and to explore the main muscle groups that affect the active movement and spasticity of the elbow flexor muscles to provide an objective reference for optimizing stroke rehabilitation.

Methods

Fifteen patients with elbow flexor spasticity after stroke were enrolled in this study. sEMG signals of the paretic and nonparetic elbow flexor muscles (biceps and brachioradialis) were detected during MVIC and FPE, and root mean square (RMS) values were calculated. The RMS values (mean and peak) of the biceps and brachioradialis were compared between the paretic and nonparetic sides. Additionally, the correlation between the manual muscle test (MMT) score and the RMS values (mean and peak) of the paretic elbow flexors during MVIC was analyzed, and the correlation between the modified Ashworth scale (MAS) score and the RMS values (mean and peak) of the paretic elbow flexors during FPE was analyzed.

Results

During MVIC exercise, the RMS values (mean and peak) of the biceps and brachioradialis on the paretic side were significantly lower than those on the nonparetic side (p < 0.01), and the RMS values (mean and peak) of the bilateral biceps were significantly higher than those of the brachioradialis (p < 0.01). The MMT score was positively correlated with the mean and peak RMS values of the paretic biceps and brachioradialis (r = 0.89, r = 0.91, r = 0.82, r = 0.85; p < 0.001). During FPE exercise, the RMS values (mean and peak) of the biceps and brachioradialis on the paretic side were significantly higher than those on the nonparetic side (p < 0.01), and the RMS values (mean and peak) of the brachioradialis on the paretic side were significantly higher than those of the biceps (p < 0.01). TheMAS score was positively correlated with the mean RMS of the paretic biceps and brachioradialis (r = 0.62, p = 0.021; r = 0.74, p = 0.004), and the MAS score was positively correlated with the peak RMS of the paretic brachioradialis (r = 0.59, p = 0.029) but had no significant correlation with the peak RMS of the paretic biceps (r = 0.49, p > 0.05).

Conclusions

The results confirm that the biceps is a vital muscle in active elbow flexion and that the brachioradialis plays an important role in elbow flexor spasticity, suggesting that the biceps should be the focus of muscle strength training of the elbow flexors and that the role of the brachioradialis should not be ignored in the treatment of elbow flexor spasticity. This study also confirmed the application value of sEMG in the objective assessment of individual muscle strength and spasticity in stroke patients.

Electrode Size and Placement for Surface EMG Bipolar Detection from the Brachioradialis Muscle: A Scoping Review

The brachioradialis muscle (BRD) is one of the main elbow flexors and is often assessed by surface electromyography (sEMG) in physiology, clinical, sports, ergonomics, and bioengineering applications. The reliability of the sEMG measurement strongly relies on the characteristics of the detection system used, because of possible crosstalk from the surrounding forearm muscles. We conducted a scoping review of the main databases to explore available guidelines of electrode placement on BRD and to map the electrode configurations used and authors’ awareness on the issues of crosstalk. One hundred and thirty-four studies were included in the review. The crosstalk was mentioned in 29 studies, although two studies only were specifically designed to assess it. One hundred and six studies (79%) did not even address the issue by generically placing the sensors above BRD, usually choosing large disposable ECG electrodes. The analysis of the literature highlights a general lack of awareness on the issues of crosstalk and the need for adequate training in the sEMG field. Three guidelines were found, whose recommendations have been compared and summarized to promote reliability in further studies. In particular, it is crucial to use miniaturized electrodes placed on a specific area over the muscle, especially when BRD activity is recorded for clinical applications.

Effects of Traditional Chinese Acupuncture Compared with Sham Acupuncture on the Explosive Force Production by the Forearm Muscles in Female: A Randomized Controlled Trial

Background

Acupuncture can effectively enhance musculoskeletal rehabilitation, with effects such as reduced pain intensity and muscle tension and decreased disability.

Objective

The purpose of this study was to determine the efficacy of traditional Chinese acupuncture (TCA) compared with sham acupuncture (SA) in explosive force production by the forearm muscles in females.

Methods

A total of 32 subjects were included and randomly assigned to two groups: TCA group (n = 16): stimulated specific acupoints including Quchi (LI11), Shousanli (LI10), Hegu (LI4), Xiaohai (SI8), Tianjing (SJ10), and Waiguan (SJ5) for 15 minutes; SA group (n = 16): using superficial needle insertion at nonacupoints without stimulation. The subjects warmed up for the 3-time isokinetic test with an angular velocity of 30°/s and then performed a set of 15 full flexion (Flex) and extension (Ext) with an angular velocity of 180°/s using the CON-TREX isokinetic test training system recorded as the pretest. After acupuncture for 15 min, perform a set of the same isokinetic movement isokinetic records as the posttest. The average max torque, average work, average power, average peak power, average max speed, and total work were collected to evaluate the forearm explosive force changes. Use two-way repeated measures ANOVA to compare the difference before and after acupuncture between two groups.

Results

The results showed that acupuncture conditions (sham acupuncture as well as true acupuncture) and the intervention times (not acupuncture or acupuncture for 15 min) have a significant interaction effect on forearm explosive force and joint stiffness (P < 0.05). The simple main effect showed that the selected parameters of the TCA group increased significantly after acupuncture (P < 0.05), while the SA group did not (P > 0.05). We speculate that the activation of muscle may be related to the selected acupuncture points.

Conclusion

Acupuncture can produce excitation in motor nerves and muscles, and nerve stimulation increases the recruitment of motor units, thus improving the muscle explosive force.

The Flexion Initiation Test and an Evidence-Based Diagnostic Algorithm for Distal Biceps Tendon Tears

Purpose

The purpose of this study was (1) to assess the flexion initiation test’s (FIT) ability to detect distal biceps tendon tears (DBTT) in a cohort of consecutive patients presenting with elbow pain and (2) to generate a reliable evidence-based diagnostic algorithm using a combination of both the FIT and hook tests.

Methods

We performed a retrospective review of 125 consecutive patients who presented with elbow pain, all of which had the FIT and hook test performed prior to imaging/further intervention. The integrity of the tendon was determined during surgery or by magnetic resonance imaging. Sensitivity, specificity, positive predictive value, and negative predictive value were determined for the FIT and hook test.

Results

Our evidence-based diagnostic algorithm showed that when both test results are in agreement, there is a 100% diagnostic accuracy for detecting what prior authors have termed surgically indicated tears (complete ruptures and high-grade partial tears) and biceps pathology that can be treated with nonoperative management. The FIT demonstrated 100% sensitivity for surgically indicated tears. The hook test demonstrated 100% sensitivity for complete ruptures, but 18% sensitivity for diagnosing partial tears.

Conclusions

The FIT, which is aimed at improving diagnostic acuity of high-grade partial thickness tears, demonstrated a 93% sensitivity and 96% specificity overall and a 100% sensitivity for complete ruptures and high-grade partial tears. The evidence-based diagnostic algorithm using the combination of the FIT and hook test demonstrates high accuracy for the diagnosis of both complete and high-grade partial DBTTs. The methodology may help to prevent diagnosis delays, improve patient education, and preserve the option for timely primary surgical repair in the treatment of DBTTs.

Level of Evidence

Level IV, diagnostic.