I have a bigger post coming up on the overall approach to internal development, given the plethora of styles, methods and teachers out there, not to mention the increasingly dense foliage of even my own stuff, which was originally intended to streamline, mainline, and mainstream these esoteric practices.
But before I get to that, I wanted to quickly field a softball on the perennial topic of flexibility. A lot of people see my yoga pics or they're just interested in yoga anyway, and they write to ask about the relation between yoga flexibility and Tai Chi relaxation - is that the same thing or what?
It's not the same thing. I do Ashtanga yoga just because I like it and because as long as I'm dragging around a human body I need to keep it minimally tuned up. I don't have a whole lot of interest in the physical body - mine or anybody else's. Physical life is fleeting. The body is just baggage that we have to drag around temporarily while serving out our sentence here on the Earth plane. For example, I own a car but just because that's useful/necessary in the USA. I'm not into cars. They don't interest me. I don't watch NASCAR on weekends or tinker under the hood or slaver after a Lamborghini. But as long as I do feel I need to own one, I don't want to crap out on 405 some cold night, thus I do the minimum of keeping it oiled, lubed, tuned and decent enough tires. I don't care but if you own one you have to go through the motions.
In this view of the physical, I'm an oddball yogi in that the vast majority of yogi's that I have met so far (SWEETEST and NICEST people in the universe!) while they pay lots of lip service to Patanjali and enlightenment and all that, frankly for the most part, operationally? They are 100% physical people. They LOVE, WORSHIP and ADORE the physical body (especially their own of course, like all of us in that way). Most people in the game are total Snapchat yogi's and I understand why. It's easy to fall in love with asana porn of how cool you or somebody can do some pose to impress others (supposedly. Actually nobody cares, people are interested in themselves.)
There's a vague genuflection to Rama or whatever, a vague expectation that someday (maybe after 5th Series!) we're gonna hit the big E of enlightenment or permanent bliss or whatever. But in practice most people just wanna get on the mat and sweat and stretch and bind. And we have good doctrinal support for that attitude. After all, Pahtabhi Jois himself famously said: "Ashtanga yoga is 1% theory, 99% practice".
Anyway, the extreme flexibility you seen in advanced Ashtanga yogi's and yogini's in their Snapchat asana porn is the result of natural attribute combined with a lot of hard and sustained work. For example, the photo above shows one of my Ashtanga teachers performing Hanumanasana (front splits, named for the monkey god Hanuman who took a huge leaping lunge between India mainland and Sri Lanka in the Ramayana story). That pose is in the 'Advanced A' (3rd) Series of Ashtanga yoga. From a yoga point of view, it takes some work and doing to evolve to where you perform that routinely.
But that yogic flexibility does NOT correlate at all with the softness that is the bedrock and hallmark of Tai Chi. Most yoga people (SUPER sweethearts that they are!) are very uptight and clenched up both physically and psychologically. It makes sense doesn't it? These are people who believe that if you can just force yourself to do every goddamn little dinky ass thing just PERFECTLY RIGHT then you will I don't know become enlightened or at least get a gold star or something. That's a beautiful community of precious souls.
Tai Chi is totally different. Tai Chi maybe because of its vague and tenuous historical connection to martial arts takes a more practical attitude. Since flexibility per se is not required for pursuing the real goal of Tai Chi (radical internal power!) therefore it is not stressed or prized, nor is it striven for in any explicit fashion.
However, most any professional instructor of Tai Chi, regardless of age, style or gender, is nevertheless able to drop into the splits or any other straightforward (but sometimes regarded as extreme) stretch. For example, forget about yoga and Hanumanasana for a minute. Here is a photo of me snapped this morning doing a simple Chinese-style full 'wall splits' just for the hell of it (I do not practice Ashtanga 3rd Series) just as any professional Tai Chi instructor could do, regardless of age/gender (59/male)
It's not beautiful yoga asana porn, because Chinese don't care so much about that. But as for the 'flexibility' - how can that be done, given that we Tai Chi types don't explicitly train for it? It's because a Tai Chi teacher has become soft. That's more important for internal energy than the rigid extension training of yoga or dance. And this soft quality emerges naturally just due to patient work on the Tai Chi foundation of relaxation. So relaxation brings flexibility as a natural by-product, but the reverse is not true: flexibility (as in yoga) does not automatically and naturally bring relaxation.