Requiring strength and balance, Bakasana ( Crane Pose) teaches the basic principles of all the other arm balances. Obviously, the strength of forearms and arms is important; the triceps (back of the upper arm) must be active to support full extension of the elbow joint. But also the muscles of the core must work. The abdominal muscles play a key role in aiding the arms.
When temperatures drop, we cover ourselves with puffy jackets, burrow underneath blankets, and keep an endless supply of warm tea on standby. Maybe yoga is the last thing on your mind (especially when it involves abandoning your protective layers). But unlike the temporary fixes that you reach for when you're feeling chilly, yoga generates warmth from the inside out. These static and dynamic postures are sorta like your body's personal space heater that you can turn on whenever you need it.
The breath plays an important part here. If the breath is held, a hardness pervades the abdomen and disallows what Iyengar considers the full benefits to the internal organs. It is therefore important to keep the abdomen as relaxed as possible, and the breath moving and soft. Although it is difficult to breathe as deeply when in the pose as you might if you were just sitting, the breath nonetheless should be as relaxed as possible.
