Standing feet at shoulder width, extend in a circular way your arms forward at hips height. Then, bring your arms back to your lower belly. Very similar to this at 2:13 but with hands facing to the ground. At first, the full circle should be done at that speed, in order to connect your arms muscles and fascia with those of the torso. When extending the arms you'll feel the lumbar region stretching. When bringing them back, you'll feel some contraction in the lower abdomen. Soon you'll notice the out-breath matches with the arms expansion and the in-breath with the contraction. Once you're comfortable with it, slow down the speed gradually to around 20 seconds per full cycle. Eventually you'll notice chi-energy-vibrations on your arms, and the extending to the torso and fully body. These vibrations will grow and the air where your arms display will be felt thicker. You can make use of intention to broaden that sensation to all your surroundings. Then, if you focus inside, your body will be felt empty.

Please, keep your knees slightly bent and let your weight rock slightly forward and backward at the soles of the feel. All by itself, the lower abdomen will go forward when the arms go backwards, and vice versa. Much like rowing. Eventually the whole movement happens by itself, your're kind of watching what's happening.

A nice variation is doing the arms cycles in sequence. That is, your right arm doing an anti-clock circle with a 1/4 to 1/3 delay from your left arm (doing a clock circle). In this exercise, slightly shift weight from leg to leg, following the circles. Here you can notice the soles of the feet doing the eights I mentioned before. The arms circles may be done with different sizes. If you do them small and closer (and slow), you'll notice how one arm pull-push the other. This sensation will grow to the whole torso.