Re: It's not You, It's Me
I tend to be a "look to the source" type of person, so when I first started getting exposed to "internal strength", I started looking at it from an aikido perspective, which led to me looking at who was doing it from a Daito ryu perspective, which led to me looking at where those skills may have made their way over from China, which led me to looking at Southern vs. Northern models which ultimately had me land at the six harmonies definition via the neijia as the source of what I was starting to understand as "internal strength".
"Aiki" as it seems to be used here, is more an application of what I would consider "internal strength" principles, so I seem to stand with the folks that say without "internal strength" there isn't really "aikido" as the founder was describing it. I also think the founder was a bit of a nut with a god complex that allowed for a pseudo cult to spring up which his son then marketed the heck out of into a worldwide movement which has since been branded and re-branded to be whatever the heck people wanted it to be. So from the source of "aiki" comes many later versions and interpretations of "Aiki-do".
I don't really think "internal strength" or "aiki" is all that and a bag of chips for most people simply because the law of percentages dictates that the majority of the folks doing it will not 1) Work hard enough to get anywhere (it takes a TREMENDOUS AMOUNT OF WORK) 2) Will not think through the logic and ramifications to the degree it takes to train the body to skillfully manifest the core tenets of 6h and then go back to 1 which is more physical training and conditioning.
I think what a lot of people are considering to be "internal strength" begins and ends with what would be normally classified as "stupid jin tricks" that can be applied with an understanding of ground/gravity power, plus cheated or amplified by bracing and solid physical structure (which is somewhat ironic because to really do "stupid jin tricks" well, you shouldn't need much bracing and structure, but that's a different convo). To Demetrio's point, if the extent of your martial arts practice is practicing ritualistic role-playing via dress-up and Asian cultural dancing, then this level of "internal strength" I describe is going to be pretty awesome.
If you look at the 6h definitions, then you'll see there are a bunch of deeper areas of study within the model of "internal strength" beyond ground/gravity (and there's some very specific implications regarding correct application of ground/gravity powers) and where they're bridged by types of long muscle and body connectivity exercises. The latter can be done with varying degrees of complexity and cohesiveness - which then gets into which parts of the body act as the control centers for these unified conditioning and skill building activities - THEN there's how they get applied in the physical sense which is why it's still kinda sorta handy to have a martial arts container that allows you to express them.
I think where it gets more interesting from an "internal strength" perspective is with regard to the type of body connectivity that results from the training, some pretty staggering implications regarding the amount of power you can generate when all the conditioned and connected gears work together and the notion of this type of study being part of what's referenced in the ancient texts regarding "the superior man". Especially as the body ages and certain types of musculature fade, there's some interesting evidence that suggests this type of cohesiveness retains greater potency into a more advanced age than the normal localized muscle development.
Do I think there's advantages to this type of training from a fighting/martial arts application standpoint - absolutely! But for folks in the sport fight game, I think there's better ways to train with faster time-to-market based on what's been developed already within the sporting sphere. Do I think there's opportunities for overlap, yes!! (been playing with that and I do think there are some acceleration potentials, but they hardly replace competency in standup, clinch and ground) Do I think "THIS STUFF" (internal strength and aiki) should belong in any and every martial art?? YES! BUT . . . they DO NOT REPLACE A MARTIAL ART . . . plus for those of you that don't want to work hard, this is definitely not the place for you to latch onto as a silver bullet magic power. It adds a ton more work and if you're stuck at only training it 3 nights a week, then this will at best be another kind of parlor trick.