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Muscle Activity in Snapping Triceps Syndrome

In this study, electromyographic (EMG) studies of the triceps muscle were compared in two groups of men. The triceps muscle has three parts (tendons) and is located on the back of the upper arm. When it contracts, the elbow straightens. The first group had a condition called snapping triceps syndrome (STS). The second (control) group) included normal, healthy male adults with no elbow problems.

STS is an actual dislocation of the medial triceps tendon and ulnar nerve over the medial epicondyle of the humerus (upper arm bone). The medial epicondyle is the bump on the inside of the elbow sometimes referred to as the funny bone.

The researchers suspected that the firing pattern of the dislocating triceps muscle was different from the firing pattern of a normal elbow. Fine wire electrodes were used to record the electrical activity of the muscle in both groups.

EMG activity was recorded for each elbow in five different positions from zero (full extension) to full elbow flexion. Data was recorded for all three tendons of the triceps muscle. Electrical signals were recorded and analyzed by a computer program.

The authors found no difference in the firing patterns of the triceps muscle between the two groups. These results suggest that abnormal muscle activity isn't the reason the triceps muscle dislocates.

Since the problem occurs in men who lift weights, it may be the excess bulk of the muscle displaces the muscle causing the dislocation. An ultrasound study may be the next step to measure and compare muscle bulk between the two groups.

References: Andrea J. Boon, MD, et al. Muscle Activation Patterns in Snapping Triceps Syndrome. In Archives of Physical Medicine and Rehabilitation. February 2007. Vol. 88. No. 2. Pp. 239-242.

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