Why Is My Arm Twitching!? An Inquiry.

Biology 103
2005 Second Paper
On Serendip

Why Is My Arm Twitching!? An Inquiry.

Matthew Lowe

For several days now, and as I write this paper, a muscle in my left forearm has been twitching vigorously on a regular basis. It is not painful, but I am always able to feel it while it is happening. In general, an episode of spasms begins suddenly and with great rapidity; about ten contractions per second. It then usually slows to irregularly-spaced single spasms, with the occasional double-twitch. All individual spasms are very quick; the contraction and release taking a fraction of a second. The twitch is visible: it appears that a narrow section on the right side of the large anterior muscle (the one that lifts the wrist) is being pulled forward about a quarter-inch. The visibly affected area extends over the inner elbow and about four inches up the upper arm. I had originally attributed the twitch to caffeine or stress, as I find that my left eye twitches in a similar way during periods where I am forced to drink lots of coffee and skimp on sleep. However, for the past few days I have consumed no caffeine and gotten a reasonable amount of sleep. I got some light exercise, and was moderately nervous for a musical performance last night. One possible strain on my left arm was a pain in my wrist from probably straining too hard, playing guitar for a more extended period of time than I am accustomed. Extensive stretching, massage, and more aggressive tactics have done nothing to slow the spasms, indeed, direct pressure on the area will not even stop spasms as they are occurring.

The first step in diagnosing this annoying and increasingly distressing affliction seems to be to determine what is actually twitching. It seems that only the muscle itself has the ability to actually move a part of the body, but of course muscles respond to nerve impulses. Could ligaments or tendons be malfunctioning and triggering these movements? It appears that this would not be the case, as ligaments merely connect bone to bone and tendons muscle to bone. They are made of soft collagenous tissue, and classification of these tissues are based on stiffness of the "crimp" of the tissue and its resistance to load under pressure (1). These characteristics do not seem to suggest the capability of autonomous movement. The same is the case for actual nerves. The action, therefore, must be in the muscle. Something, therefore, is triggering the irregular bonding and release of myosin heads to the actin filaments. This action is also, at a certain level, uncoordinated, because though the movement of the actual muscle is large, there is no visible translation to a bone, moving a limb. Perhaps the "power stroke" of the muscle is so short, and in a small enough section of the muscle that it overcomes the deformation curve of the tendon. However, the timescale of this phenomenon is far shorter than the muscular action I am experiencing. Perhaps the muscle in question serves another purpose. The two strongest possibilities for identity of the offending muscle, based on the line the spasms trace, are pronator teres or the flexor digitalum superficialis (2). There is little reason to suspect the second, as it is a deeper muscle, and much more of it would likely move if it were to misfire. The pronator teres appears exactly the proper size and shape. This muscle originates at the Medial epicondyle of the humerus and at the coronoid process of the ulna, and inserts at the middle of the lateral surface of the radius. In other words, at the very bottom of the humerus, a few inches down the ulna, and between them on the radius, respectively. The muscle pronates and flexes (rotates and bends) the forearm at the elbow. Though it appears that the bulk of forearm flexion is performed by the Brachialis, most pronation is done by the pronator teres, further confusing the question of why my arm remains still when the muscle twitches (3). The muscle is innervated by the median nerve, a common site of nerve compression and repetitive stress syndromes. There exists a pronator teres compression syndrome, but it is fairly rare and its symptoms include pain in the area, weakness in the hand, certain types of palsy in the fingers, and do not include twitching of the muscle (4). None of these apply to my situation.

A visit to a medical reference site querying "muscle twitch" yielded information I had assumed at the beginning of my inquiry. Barring neurological disorders such as Lou Gehrig's disease and Muscular Dystrophy, causes of muscle twitching were simple: caffeine, excessive exercise, stress, a diet deficiency. The former three I was willing to rule out in my situation, but it is possible that there has been a deficiency in my diet. Returning to institutional food has greatly increased the proportion of meat in my diet, which had been significantly reduced during the summer, and it seemed particularly high in the past week. Further research suggested that spasms and cramps could be caused by a calcium deficiency resulting from high protein or phosphate intake. A deficiency in pantothenic acid (Vitamin B) were pointed to as a cause, but several prime sources of the vitamin were part of my diet in the period in question. A high Magnesium-to-Calcium ratio in the body was another cause. It is true that most recently, green vegetables and legumes, the major sources of magnesium, had not been in adequate proportions in my diet, but this would presumably result in, if anything, a low Mg/Ca ratio Consuming foods containing lactic acid was pointed to as a possible strategy (6). In the end, it was unclear exactly what could be done on a dietary level to correct this ratio, as consuming more of one mineral would block absorption of another in a complex web, and it would be impossible to be certain of the proportions in my body without knowing the proportions in the foods I ate, without having kept careful track of what I had eaten in the period in question.

Would there, then, be anything that could be done in the short term? It seems to stand to reason that the malfunction of myocin in the muscle would be triggered by the synapses of a nerve going haywire. Is there any way that the functioning of a cluster of nerve cells could be directly impacted? A relationship between electrical pathways in the body and acupuncture came to mind. Most charts of acupuncture meridians that I was able to find related the acupoints to organs, as opposed to specific muscles or limbs, which seemed like a dead end. This was interesting, however, as it was indicated that Eastern medicine traditionally conceived of disease as a collection of symptoms rather than a unified state of the body, which would suggest that their treatment strategies would target various body aches outside of the major organs in the trunk or head (8). Another article indicated that "The change of electric activity is part of signal transduction and can precede anatomical change," but that some electromagnetic patterns in the body mapped by a SQUID (Superconducting Quantum Interference Device) are consistent with the meridian system, but not necessarily "any major nerve, lymphatic, or blood vessel" (9). The author goes on to note that "An "annealing" mechanism may play a role in acupuncture and related techniques: Small perturbations at singular points elicit a "shock" to the system - activates and shakes the biological system out of its abnormal and unstable state. After activation, the system has a better chance to settle at a normal, more stable state." It seems likely that acupuncture could have an effect on my own particular malfunction, if it is in fact related to the electrical impulses in the muscle, but it seems that to find out exactly how would require the involvement of a specialist, or, as the web seems to indicate, the purchase of a book.

In the end, this particular spasm episode will likely soon come to an end, but a few questions still remain unanswered in my mind. First: if, for instance, the spasms were caused by a nutritional deficiency, why would that macro deficiency manifest itself in one section of the body for an extended period of time? Second: another article outlining the system of nerve impulses involved in a reflex reaction demonstrated the level of communication necessary to return a reflex impulse to its point of origin. What if my left pronator teres or its median nerve thought that it was receiving an impulses and was actually responding normally? If so, what could this false impulse have been caused by? Most of my confusion arises from the specificity in manifestation of a generalized explanation. What is so different about this particular assembly?

1) Notes for a U-Michigan biomechanics course

2)Contents of upper limb and back, drawings of macro anatomical assemblies

3)Upper Extremity Muscle Atlas

4)eMedicine, Hand and nerve compression syndrome overview

5)National Institutes of Health, NIH Reference Site

6)Acu-cell, Nutritional causes of muscle spasms and cramps

7)Acu-cell, nutritional mineral ratio primer

8)The Med-Com Resource, Acupuncture primer

9)The Meridian System and the Mechanism of Acupuncture, Article on acupuncture research