T’ai Chi is usually practiced slowly so that you can fully embrace and appreciate the principles. But it can provide aerobic conditioning if practiced at a faster pace. Remember that at its roots, T’ai Chi is a form of combat training. If you were in battle, you'd be moving to save your life — literally.
You can do any of the forms, alone or in combinations of two or three. But a few guidelines apply before you can start doing T’ai Chi in the faster-paced style of Alvin and the Chipmunks.
Know the form or forms you intend to do so that you can flow through them without stopping. That means being able to do them slowly and pretty well before you move it up a notch.
Warm up well. Usually, T’ai Chi is slow enough that you may not need a true warm-up. But you need a warm-up if you’re speeding things up. Do some warm-up movements. Also, you can do the forms slowly first as a second part of your warm-up.
Keep your movements precise. Don’t get sloppy just because you are moving faster. If you can't keep the precision, slow down a tad to a speed where you can still do the movements correctly.
Start your up-tempo practice moderately. In other words, don’t go as fast as you can at the outset. When you first start trying some speed, go just a little faster than you normally do. Then you can increase the speed one small gear at a time.
Do a cool-down. If you move faster, you also need to repeat the selected forms slowly as a way to cool-down. Then you can do some of the warm-up movements as a cool-down, too.