<div style='font: 9pt ; text-align: left; '>...although it isn't really a strong distinction. Many external arts, at their highest level, become internalized. It's just that you start out using external "muscular" power. Actually, I'm pretty sure internal artists use muscular power too, but not in the normal sense. To many they consider this sort of power chi or ki.
I'm going to make a bastard attempt to summarize the differences between external and internal styles. According to the external philosophy, in order to hit someone harder, you must be stronger. So if you do a normal punch, what muscle groups do you use? Perhaps your wrist, triceps, shoulders, chest, and waist. So how do you become stronger? Get bigger/stronger muscles of course. IMO, it's sort of a "brute force" way to tackling the problem of hitting harder.
Internal stylists also want to hit harder. But instead of gaining more muscle to gain more strength, they prefer to maximize the use of the muscles they already have. The power behind their punches comes from the leg all the way up through to the fingers. It's a very coordinated use of all their muscles working as efficiently as possible to deliver a blow. Tai Chi practitioners sometimes refer to this as "chan shi jing", or silk reeling power. What they mean is that the energy starts from the ground, and propagates up through the body (from leg to hips to torso to arms to fingers) in a spiralic manner, so that they literally hit with the force of their entire bodies. This is why you have stories of small kung fu masters being able bounce off people much bigger than they. If you think about it, your legs will always be much stronger than your arms, so it makes more sense (to me at least) to utilize that energy rather than to just get bigger arm muscles. The upshot of this is that you develop "root." Because their power starts from their legs, internal stylists are very stable and it is not at all easy to off-balance them. As a result of their training, their upper body is connected to their lower body, so applying any sort of force on them is like applying force to the ground. You can try pushing the ground to see if it goes anywhere. External stylists, on the other hand, don't train to have that connection between the upper and lower body, so it's fairly easy to off balance them. It is extremely difficult for a Judo guy to throw a competant Tai Chi guy.
It all sounds nice, but there's a catch. It's much easier said than done to train your body to work this way. While anyone can throw a punch, not everyone can coordinate their bodies so that they utilize all their strength from ground up. It takes a lot of practice. Whereas a Muay Thai guy can become a decent fighter in as little as one or two years, it takes a Tai Chi guy up to ten or more years or more to <i>really</i> be able to use "internal" force. The learning curve is ridiculously high. A lot of it has to do with training your body not to work against itself, which it naturally does. That's why the "mind" in trained. But don't fret. While you train, you get all the health benefits that come with this sort of training. Training to be calm, to be relaxed, to be coordinated, to have balance, etc. will do wonders for your health. Because you utilize every part of your body, you exercise every part of your body. The advertised health benefits of Tai Chi are very real. Also, unlike external stylists, internal force doesn't really diminish with age. Whereas a Muay Thai guy is in his prime in his 20's and 30's, a Tai Chi guy is in his prime in his late 50's, 60's, and 70's. That is not to say you have to be 50 years old to be able to use Tai Chi, it just means that you can't really "max out" your training. Wang Xiang Zai, founder of the internal style of "YiQuan" (Intention Boxing), pretty much kicked everyone's as before he was 20. As he got older, he only got better. There was never really threat of a younger, stronger, faster, upstart beating him.
Anyway, I rambled long enough, and I've got work to do. It should be obvious that I'm fairly biased towards internal styles. I use to train Hapkido, which is considered external, and now I train in Wing Chun, which is internal, from the way my teacher teaches it. I also did a little bit of Tai Chi a few months back. But there are benefits to external styles, and I wouldn't recommend internal styles absolutely. For instance, if your goal is self defense, and you need/want to learn it fast, I suggest you go with boxing, Muay Thai, or Brazilian Jujitsu. If you want to lose weight, you should also go external (although it would probably be cheaper to just jog your fat ass around the block). If you want any advice (not that I'm qualified, but I have done a fair amount of research so my opinions <i>might</I> have some merit) regarding martial arts, don't hesitate to ask. As you can tell, I like to talk about martial arts. A lot.
Zhuge Liang</div>