I feel a cramp-like sensation in my leg while meditating, when I become more concentrated. Some kind of energy wants to travel through my leg nerves but because of blockage it can’t flow and my leg shakes and tries to move in some different direction.
—Akhilesh Vyas, India
In reading your note I assume that you are: 1) sitting cross-legged (on the floor or cushion), 2) the leg cramp is always in just one of your legs (not both), and 3) that the cramp and shaking takes place after meditating for a while (and not immediately).
Based on my notes above, I would say you should seek out some guidance from a competent yoga instructor on options and modifications to the sitting poses that would eliminate your problem. From a distance and in writing, I would say that at least one leg is not fully relaxed and resting. It is probably “riding up” off the floor or off the cushion in such a way that after some minutes the shaking begins because the muscles are having to hold the leg in that position and cannot relax fully as they should.
As I don’t know what you are sitting on, I’d like to offer you some suggestions:
1. Don’t sit on the bare floor or other flat surface.
2. Instead: Sit on a folded blanket or cushion so that your knees are BELOW your hips. The elevation caused by a blanket or cushion will drop the knees lower than the hips and more likely allow the legs to be cushioned and supported in the area of the thighs and knees. You can even stuff a small pillow (or other soft object) under your thighs in order to support them.
3. Your back should be upright in its natural curvature and not bent forward or backward but upright AND relaxed into its most natural but erect posture.
4. Hands upward on the thighs, either out toward the knees or in at the junction with the thighs.
5. Your knees should not RIDE HIGH, sticking up.
6. You may even wish to consider meditating in a straight back chair (not a soft, easy chair): one without “arms.” Here, too, the knees should be slightly lower than the hips. Again, a folded blanket or cushion can help with that.
7. Your head should be level and parallel to the ground, and not jutting forward but slightly back.
During your meditation, from time to time, check your posture. There is, for most people, a natural posture that can be achieved with some experimentation: one that keeps the chest up, spine erect, head level, arms, palm-upwards on the thighs, knees below the thighs.
Try some of these things and let us know if you find relief! OK?