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. 2014 Feb 26;2(2):2325967114523902.
doi: 10.1177/2325967114523902. eCollection 2014 Feb.

Glenohumeral Function of the Long Head of the Biceps Muscle: An Electromyographic Analysis

Peter N Chalmers  1 , Johannes Cip  2 , Robert Trombley  1 , Brian J Cole  1 , Markus A Wimmer  1 , Anthony A Romeo  1 , Nikhil N Verma  1
Affiliations

Glenohumeral Function of the Long Head of the Biceps Muscle: An Electromyographic Analysis

Peter N Chalmers et al. Orthop J Sports Med. .

Abstract

Background: Optimal treatment of superior labral anterior-posterior (SLAP) tears is controversial, in part because the dynamic role of the long head of the biceps muscle (LHBM) in the glenohumeral joint is unclear. The aim of this study was to determine dynamic LHBM behavior during shoulder activity by studying (1) the electromyographic activity of the LHBM during shoulder motion, (2) the effect of elbow immobilization on this activity, and (3) the effect of a load applied to the distal humerus on this activity.

Hypothesis: The LHBM would not play a significant role in active glenohumeral range of motion.

Study design: Controlled laboratory study.

Methods: Thirteen normal volunteers underwent surface electromyography (EMG) measurement of the LHBM, short head biceps muscle (SHBM), deltoid, infraspinatus, and brachioradialis during shoulder motion from the neutral position (0° of rotation, flexion, and abduction) to 45° of flexion, 90° of flexion, 45° of abduction, and 90° of abduction. These motions were repeated both with and without splint immobilization of the forearm and elbow at 100° of flexion and neutral rotation and with and without a 1-kg weight placed on the lateral distal humerus.

Results: Mean EMG activity within the LHBM and the SHBM was low (≤11.6% ± 9.1%). LHBM activity was significant increased by flexion and abduction (P < .049 in all cases), while SHBM activity was not. EMG activity from the middle head of the deltoid was significantly increased by loading with the shoulder positioned away from the body (ie, in abduction or flexion). When compared with the unloaded state, the addition of a distal humeral load significantly increased LHBM activity in 45° of abduction (P = .028) and 90° of flexion (P = .033) despite forearm and elbow immobilization. The SHBM showed similar trends.

Conclusion: In normal volunteers with forearm and elbow immobilization and application of a load to the distal humerus, LHBM EMG activity is increased by both glenohumeral flexion and abduction, suggesting that this muscle plays a dynamic role in glenohumeral motion with higher demand activities.

Clinical relevance: Biceps tenodesis may result in dynamic change within the glenohumeral joint with higher demand activities.

Keywords: biceps tendon; electromyography; labral tear; long head of biceps tendon; superior labral anterior posterior (SLAP) tear; upper extremity immobilization.

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Conflict of interest statement

One or more of the authors has declared the following potential conflict of interest or source of funding: This study was funded by grants from the Arthroscopy Association of North America and KFx Medical Inc. B.J.C. receives royalties from Arthrex and DJ Orthopaedics; is a paid consultant for Arthrex, DJ Orthopaedics, Johnson & Johnson, Regentis, and Zimmer; has stock or stock options in Carticept and Regentis; receives research support from Johnson & Johnson, Medipost, and Zimmer; receives publication royalties from Elsevier, Lippincott, Smith & Nephew, and WB Saunders; serves on the boards of the American Academy of Orthopaedic Surgery, the American Journal of Orthopaedics, the American Journal of Sports Medicine, Cartilage, the Education Committee of the Arthroscopy Association of North America, Elsevier, the International Committee of the Arthroscopy Association of North America, the Journal of Bone and Joint Surgery, the Journal of Shoulder and Elbow Surgery, and the Arthroscopy Association of North America. A.A.R. receives royalties from Arthrex; serves on the speaker’s bureau for Arthrex; serves as a paid consultant for Arthrex; receives research support from Arthrex, DJO Surgical, Smith & Nephew, and Ossur; receives other financial support from Arthrex and DJO Surgical; receives publication royalties from Saunders/Mosby-Elsevier; serves on the boards of the Journal of Shoulder and Elbow Surgery, SLACK Inc, Orthopedics Today, Orthopedics, Sports Health, Techniques in Shoulder and Elbow Surgery, Operative Techniques in Sports Medicine, the Orthopaedic Journal of Sports Medicine, The American Orthopaedic Society for Sports Medicine, the American Shoulder and Elbow Surgeons, and the Arthroscopy Association of North America. N.N.V. receives royalties from Smith & Nephew; serves on the speaker’s bureau for Arthrosurface; serves as a paid consultant for Smith & Nephew and Arthrex; has stock or stock options in Omeros; receives research support from Arthrex, Smith & Nephew, Athletico, Conmed Linvatec, Miomed, Mitek, and Arthrosurface; receives publication royalties from Vindico Medical, Orthopedics Hyperguide, and Arthroscopy; serves on the boards for the Journal of Knee Surgery, Arthroscopy, SLACK Inc, and the Arthroscopy Association of North America Learning Center Committee.

Figures

Figure 1.
Figure 1.
This series of clinical photographs shows electrode placement. (A) Anterior view demonstrating electrode placement on the long and short heads of the biceps. (B) Lateral view demonstrating electrode location on the middle head of the deltoid. (C) Posterior view showing electrode placement on the infraspinatus. A latissimus dorsi electrode is also shown, although this electrode was not used for this particular study.
Figure 2.
Figure 2.
Cadaveric anatomical dissection showing that the long and short heads of the biceps exist as separate fascicles without cross-talk up to their coinsertion at the distal tendon and are thus candidates for separate electromyographic data collection.
Figure 3.
Figure 3.
Mean maximal manual testing–normalized percent electromyographic (EMG) activity in the long head of the biceps muscle (LHBM) both with and without splint immobilization and both with and without elbow loading with the shoulder in the neutral position and with motion to 45° of abduction, 90° of abduction, 45° of forward flexion, and 90° of forward flexion. Significant differences between mean EMG activity in the splinted and nonsplinted (within the loaded and unloaded states) and loaded and unloaded (within the splinted and nonsplinted states) are denoted by asterisks. Error bars represent 1 standard deviation.
Figure 4.
Figure 4.
Mean maximal manual testing–normalized percent electromyographic (EMG) activity in the short head of the biceps muscle (SHBM) both with and without splint immobilization and both with and without elbow loading with the shoulder in the neutral position and with motion to 45° of abduction, 90° of abduction, 45° of forward flexion, and 90° of forward flexion. Significant differences between mean EMG activity in the splinted and nonsplinted (within the loaded and unloaded states) and loaded and unloaded (within the splinted and nonsplinted states) are denoted by asterisks. Error bars represent 1 standard deviation.
Figure 5.
Figure 5.
Mean maximal manual testing–normalized percent electromyographic (EMG) activity in the middle head of the deltoid muscle both with and without splint immobilization and both with and without elbow loading with the shoulder in the neutral position and with motion to 45° of abduction, 90° of abduction, 45° of forward flexion, and 90° of forward flexion. Significant differences between mean EMG activity in the splinted and nonsplinted (within the loaded and unloaded states) and loaded and unloaded (within the splinted and nonsplinted states) are denoted by asterisks. Error bars represent 1 standard deviation.
See this image and copyright information in PMC

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