Body and Breath - Yoga Shop Talk

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Yoga shoptalk, March, 2002

Question: New students often ask with some concern why they shake so much, even in a basic beginner's class. I explain that this is normal and even necessary to begin the body's transformation. However, I am a little unsure how to explain the phenomenon from a physiological perspective. Can you offer a more in-depth explanation?

Answer: The immediate cause is cyclical activity of motor neurons. When a limb is held in a position of balance, especially in a state of light to moderate isometric tension, trains of nerve impulses from motor neurons in the spinal cord and brain stem momentarily favor muscles on one side of a joint, and the next moment favor their antagonists on the other side of the joint. An oscillation is thus set up that we see as shaking. The time frame of these oscillations can also speed up so that it feels like a vibration or an edginess that one interprets as nervousness.

Apart from activity of motor neurons and muscles, it is difficult to pinpoint the origins of the controlling influences that initiate these cycles, other than to surmise that other parts of the brain (such as the cerebellum and basal ganglia) are involved. But the oscillations are plainly hard-wired into the nervous system. Recall the famous video clip of a fireman holding a two-year-old child who was shaking after the Oklahoma City bombing. And at any given time on the evening news, we may see the same whole-body shaking or just a chattering of teeth in older children and adults who have survived other traumas. Also recall the semi-involuntary oscillation of bouncing the knee up and down that occurs when you are delayed getting to the bathroom or when you are faced with a period of extreme excitement such as a tense moment in an action movie. And finally, the oscillations and tremors that are characteristic of Parkinson's Disease are lying in wait for those who for one reason or another are susceptible to that condition.

Your advice to students was sound in that it is fine to reassure them that the shaking seen in beginners is normal and can ordinarily be expected to diminish over time. It does bear watching, however, and if it does not go away in a week or so, a reduction in the intensity of practice is indicated. And if I might make one suggestion to you in your role as a teacher, it would be to avoid the additional commentary "and even necessary to begin the body's transformation," which scientifically sounds a little glib.