Tai Chi Push Hands Exercise
The community classes generally focus on the health aspects of Tai Chi. However, Tai Chi is first and foremost a martial art. Behind the smooth and flowing movements is a deadly intention. Although most prefer to visualize nice things while practicing, others may choose to practice "shadow boxing" - in which each movement is seen as a block or a blow to an enemy.
In this picture, I practice a "push-hands" exercise with my sister: This is the part where she gets cocky and tries to push me off balance - unsuccessfully!
Push-hands is designed to develop one's ability to be intentional as well as to relax completely when an opponent grabs on to your force and tries to use it against you. Although there are many push-hands exercises, the most basic is to get into basic Tai Chi stance, Connect hands with your partner and Push towards their center (while connecting with your own), until they yield by shifting their weight. If they wouldn't have fallen over without shifting their weight, you are not doing the exercise correctly. Your intent is to push through them.
Keeping the hands connected, your partner then pushes back towards your centerline, at which point you must yield (by shifting your body-weight) in order to avoid being pushed off balance. This basic pattern can continue as a meditative exercise, with each person exploring the other's structural weaknesses - whether through gentle energetic engagement or more forceful attempts to push the other person over. A trade secret - and the healers approach - is to adopt the intention of opening any places of energetic blockage in the other person. The way to do this is to find their structural weaknesses and through this give them opportunities to relax more deeply into their bodies, finding greater balance and strength.