Purpose
The function of the brachioradialis muscle is controversial. The objective of this
study was to determine primary and secondary functions of the brachioradialis under
various loading tasks as measured by EMG.
Methods
Ten healthy individuals (9 men, 1 woman; average age, 34 years ± 10; average height,
175 cm ± 7; average weight, 76 kg ± 13) performed elbow flexion with the forearm in
1 of 3 positions (neutral, pronation, and supination) with 4 different loads (0, 22,
45, and 67 N). The elbow was flexed to 90° as the volunteers performed 2 separate
movements: (1) from full supination to neutral and (2) from full pronation to neutral
using 4 different loads (0, 9, 18, and 27 N). Each movement started and ended in supination
and pronation, respectively. Fine-wire EMG electrodes were placed in the brachioradialis,
and kinematic data were collected using an electromagnetic motion analysis system.
The EMG data were reported as a percentage of maximal voluntary isometric contraction
and were ensemble averaged from 5 trials of each exercise condition for statistical
analysis.
Results
No difference in muscular activation was found during elbow flexion tasks in the 3
forearm positions. Significantly greater activation was found during concentric (23%
maximal voluntary isometric contractions ± 5% maximal voluntary isometric contractions)
than during eccentric (11% maximal voluntary isometric contractions ± 5% maximal voluntary
isometric contractions) phases during elbow flexion. Brachioradialis mean activity
during concentric pronation and eccentric supination with the heaviest loads 18 and
27 N was significantly greater than activity during concentric supination and eccentric
pronation.
Conclusions
The greatest EMG activity recorded from the brachioradialis occurs during elbow flexion
tasks regardless of forearm position indicating that the primary function of the brachioradialis
is as a consistent elbow stabilizer during flexion tasks. During rotational tasks,
more EMG activity was recorded during pronation compared with that during supination
tasks indicating a secondary function of the brachioradialis as a pronator.
Key words
To read this article in full you will need to make a payment
Purchase one-time access:
Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online accessOne-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:
Subscribe to Journal of Hand SurgeryAlready a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
References
- The anatomy of the human body.in: Seventh ed. Hitch and Dodsley, London1756: 90
- Morris human anatomy.in: P. Blakistons Sons and Company, Philadelphia1925: 416-422
- Last's anatomy regional and applied.Churchill Livingstone, London1994 (989–989)
- Anatomy—a regional study of human structure.in: Fifth ed. WB Saunders, Philadelphia1986: 126
- Human anatomy.in: Lippincott, Philadelphia1923: 586-598
- Variation of muscle moment arms with elbow and forearm position.J Biomech. 1995; 28: 513-525
- Electromyographic study of the elbow flexors and extensors in a motion of forearm pronation/supination while maintaining elbow flexion in humans.Tohoku J Exp Med. 1998; 186: 267-277
- Technical considerations for electromyographic research on the shoulder.Clin Orthop Relat Res. 1997; 335: 140-151
- Anatomical guide for the electromyographer.in: Thomas, Springfield, IL1994: 35-36
- Electromyographic analysis of the deltoid and rotator cuff muscles in persons with subacromial impingement.J Shoulder Elbow Surg. 2000; 9: 519-523
- An analysis of symmetry of torque strength of the forearm under resisted forearm rotation in normal subjects.J Hand Surg. 2006; 31A: 801-805
- Muscle synergies and isometric torque production: influence of supination and pronation level on elbow flexion.J Neurophysiol. 1993; 70: 947-960
- Electrophysiological studies of the biceps brachii activities in supination and flexion of the elbow joint.Tohoku J Exp Med. 1994; 173: 259-267
- Inhibitory projection from brachioradialis to biceps brachii motoneurons in human.Exp Brain Res. 1996; 111: 483-486
- International Conference on Surgical Rehabilitation of the Upper Extremity in Tetraplegia.J Hand Surg. 1979; 4: 387-390
- The upper limb in tetraplegia.in: George Thieme, Stuttgart1978: 53
Article info
Publication history
Accepted:
July 25,
2008
Received:
December 3,
2007
Footnotes
No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.
Identification
Copyright
© 2008 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.
