Tai Chi develops foundations of balance, so with practice less effort to achieve balance is required. This exercise explores the plane of movement that runs vertically through the side of your body, which is a very useful plane of movement to use as a foundation for balance. If you reach your arms out as if they were wings and circle them up to the top of your head, your hands and arms will be moving along this plane.
This idea of a plane of movement is very useful to use as a standard to improve your posture and movements. A plane is an abstract measure of perfection, and so it's impossible to completely to conform to it. In fact, it would be unhealthy to force yourself to move in a perfectly straight line- everyone has a unique body that moves best along the idiosyncratic limits of that body. By keeping a plane in mind as a guide for movement, however, strenuous habits of movement, tension, and injuries can be healed.
To start this exercise, stand in a basic stance and bring your attention to your body. It helps to bring your awareness to your hands- specifically your palms. Your palms are useful for reaching further awareness of your body because of the amount of nerve endings they contain. Focus on your hands, and extend this focus out into the rest of your body.
Find a rate of breathing that is comfortable and that also fills your lungs completely. It may help to maintain a count of five to eight while inhaling and exhaling.
When you have reached a rhythm in your breathing, during an exhale, raise your arms until they are held at a ninety-degree angle to your body. Hold your palms upwards.
Maintain your posture here for several breaths. Become aware of the growing fatigue in your arms and shoulders as the weight of your arms becomes harder to bear. This is inevitable. While paying attention to the growing strain on your arms, seek out larger muscles groups in your shoulders and back to bear the weight your smaller muscles cannot. This will guide you towards the origin of where your arms are most efficiently lifted.
While holding your arms out at your sides, keep the horizontal plane between your arms in mind. Of course, you won't be able to maintain a perfect harmony with the plane, but it serves as a guide for finding your body's ideal point of balance.
If you find yourself becoming rigid, you are trying too hard to conform to the plane. If this occurs, imagine your arms are holding two large exercise balls, one balanced on each elbow. Imagining these circular shapes will allow your arms to bend slightly at their joints.
In summary, from a balanced stance raise your arms to your sides along a horizontal plane. To prevent becoming too rigid, allow your arms to bend slightly at their joints as if each arms was holding up a giant ball. See the diagram below- the horizontal line is the ideal plane for your arms to rest at, while the circles above this plane provide a guide for your body's unique deviations.
The contrast between these two shapes- the perfectly straight plane and the completely non-straight circles, will guide your body towards its natural shape. Finding this natural shape for your body's perfect balance can take years to discover, although you will improve with each practice.
This exercise is highly beneficial for your back and posture, as you will discover more efficient ways to carry your weight, and you will also discover where your tensions are held so you may be conscious of releasing them.