As with breathing (that I discussed in another post: Breathing and throwing punches), for those who are seasoned in combat training will know how to do good rooting when throwing punches. So what I'm talking here? I want to let those tai-chi practitioners who only train for health reasons to understand that they can, at the same time, learn how to throw punches, perhaps just a bit heavier than an average untrained person, through paying attention to one's breathing and rooting.
First the basic knowledge. The basic knowledge is that when one throws a left punch, one's right leg should stand firm and hold 100% of one's body weight, and with his left leg acts as a balancer at an angle to the main root (i.e. right leg). A related question, what balance the balancer? In a straight forward punch, it is the toes of the main root (how about a hook? try figure it out by yourself).
The above knowledge is important, otherwise the reaction force will be hitting back to yourself!
Rooting exercise in the classical way is for one to push oneself at different stance, some double weighted (i.e. equal weight on both feet) and some single weighted. The former exercises are for rooting in "wrestling", while the latter exercises are for rooting in "punching". If one can be trained in both, one will be more prepared to do combat training.
Why rooting training is important in doing a punch? Or to what physiological benefits can it achieve? Firstly, through rooting training, the force of your leg (which is stronger than your arm) can add on to the power of your punch. Secondly, rooting training can help build up a good structure, so that force will not be dissipated through unnecessary motions (like wobbling, arising from a weak structure) when the punch is on impact.