First, you have to distinguish between dizziness and nausea. Nausea is the feeling of queasiness in the stomach, as if you are about to vomit, and can be caused by disturbances in the inner ear or incorrect pressure on the abdominal organs. Dizziness is most often experienced in the skull with a feeling of lightheadedness, ringing in the ears, difficulty focusing the eyes, and loss of balance.
Dizziness can have many causes, from the serious (strokes and tumors) to the mundane (temporarily restricted blood flow from standing too quickly, commonly known as a headrush). If you experience one or both on a regular basis, you should consult your physician.
Nausea and/or dizziness in your yoga practice can also be red flags if experienced to a debilitating degree, says Robert Gray, director of the Park Boulevard Yoga Center in Oakland, California. "First, ensure you are not practicing at the wrong time with regard to your eating cycle," says Gray. "Don't be stuffed nor starving. Empty your bowels and bladder. Hydrate to a reasonable level before you begin, then refrain from drinking during your practice. For women, where you are in the cycle of your menses is significant too, and there may be days when backbends are just not for you."
But Gray also explains it this way: "Inside our body is a living mammalian core that extends from the anus to the top of the head and encompasses all our organs, glands, blood vessels, and nerves. It is woven together and to the spine with webs of connective tissue," he says. "All yoga postures are designed to effect this inner core. If our postures do not honor the integrity and intelligence of this core, we can experience symptoms like nausea and dizziness.
"To do a backbend, or any posture for that matter, we must use the strength of our arms and legs. If our shoulders and hips are restricted, the strength of our arms and legs will violate the integrity of this core body."
So what can you do to prevent nausea and dizziness? Gray offers these suggestions: Work at continuing to open the hips and shoulders with standing poses and seated twists. In the backbends themselves, concentrate on relaxing your neck. First, lie on you back with your legs relaxed and comfortable. Let the force of gravity soften your voice box and move it back into the neck vertebrae. The soft tissue from the upper lungs to the inner ears and brain should also be relaxed.
Lie very still and observe the quality of your breath. Feel and remember this relaxation in the neck and try to maintain it as you move into the backbend. Remember to move slowly and listen closely to what your core body is telling you.