Is it posible for someone to go from display, competitive fighting to practical fighting if given the motivation and training?
Yes, and many do.
So, there’s a few things to understand. Most of these are fairly simple, but aren’t common knowledge outside of martial arts communities. The training itself will be structured differently. There will always be some, “leftover,” muscle memory from prior training, however this matters way less than it may sound. Your outlook, combined with what you know is probably the most important difference.
With some exceptions, martial arts training will assume you’re starting from zero. You have no hand-to-hand background. Even if you do have a background, you’ll go through the motions again. This is partially because there may be discrepancies between what you’ve already learned and the new martial art you’re picking up. In some cases, the martial arts may be completely incompatible. This is rare, but it can happen.
If you’re in a traditional class, you’ll start with the basic rules of the school. How to stand, how to prepare for class, how to interact with your class mates and instructors. From there you’ll transition to basic stances. You’ll be instructed on how to move, and how to hold your body. Gradually you’ll move into things that, as someone without training, you’d think of as techniques, such as basic strikes. As you go, you’ll learn the proper names. Gradually you’ll learn more complicated strikes, learn to move from one strike directly into the next. At some point you’ll learn set routines of moves which can be demonstrated. Along the way, you’ll be drilling with everything you’ve learned until you can execute the movements flawlessly.
In practical training, it’s also going to start with conversation, but the content is going to be very different. For self-defense, the first thing you’re going to learn is threat assessment. There is a similarity here, worth discussing, in both cases the instructor begins by talking about what is most important in your training. For a traditional school, that’s “planting the seed,” for the martial art’s philosophy. For a practical class, this is telling you how to apply what you’ll learn. From there it will quickly cover stances. After that, practical classes will go directly into specific techniques. You may never learn some of the basic techniques that a traditional martial artist would consider, “fundamental,” because there’s no application. You will never learn a kata. If you’re taught a combination, it’s with the express purpose of using it. You will get into things that traditional schools consider advanced very quickly. You’re going to be training with partners, possibly from day one, but long before any traditional martial arts school would let you touch another student. When the class is over, you will be ready to use what you’ve learned in the world.
You cannot compact years of training into eight weeks, however, you don’t need to. Real world combat is messy. While traditional martial arts will teach you to execute techniques flawlessly (eventually), practical training looks at that as unnecessary. If you’re going to use this in a real fight, it doesn’t matter if it’s flawless, the only metric that matters is, “can you make it work?”
I can’t speak for the methodology of competitive sports training, though I do know people who’ve transitioned from traditional into sports, and from sports to practical. I don’t, personally, know anyone who’s run through all three, but over a long enough timescale this should be possible.
It’s also harder to lock down what someone’s training would look like if they were coming out of a non-traditional school. The example that comes to mind are recreational versions of modern practical forms, such as Krav Maga, though some MMA schools would also fall into this category as well.
As I mentioned, muscle memory will linger. This can be a problem for someone with a practical background moving into a recreational martial art. You’ve trained yourself to execute very specific movements, and being asked to subtly adjust them can be remarkably difficult. The basic problem is that practical training tends to permit a kind of sloppiness. Because the goal is to be able to use it in a real situation, being, “perfect,” doesn’t matter. In a real fight, you’re going to be adjusting to fit the situation anyway. However, a traditional school wants to improve the technique, on the idea that if you can execute it perfectly, you’d be able to make those adjustments.
I’ve said this twice, so I should probably clarify, the sloppiness that practical martial artists exhibit isn’t a vulnerability. It’s not beautiful and it doesn’t need to be. It needs to work on another person in the real world; where fights get messy. I was once advised that, “every fight will end up with you both on the ground.” It’s not pretty, and it doesn’t fit the idea of how a fight, “should,” look. But if you’re looking for real things to match their cinematic counterparts, you’re signing up for a lifetime of disappointment.
Beautiful technique is just that: beautiful. It can be a real joy to watch, but, it doesn’t mean the martial artist knows how to fight.
Knowledge is incredibly important. It’s easy to think of “martial arts” a unified skill, but there really is a difference between technical proficiency, and an understanding of combat. This is where I really do not want to sell traditional martial artists short. An experienced artist has developed a great deal of skill, and they have come to a deeper understanding of their martial art, and possibly a deeper understanding of the world they live in. Someone with a combat training background will have a breadth of knowledge regarding how people behave in combat. In a real fight, the latter will be vastly more valuable than the former.
Outlook is a little murkier. This is your willingness to engage in violence. No martial arts instructor (regardless of their field) wants students who will casually engage in violence. It does not make good soldiers. It is actively counterproductive for sports and self-defense. It is a disaster for traditional martial arts.
For most people, the switch over to being willing to harm another human being is not easy. Obviously, this is not everyone, some people come to that decision far easier than others. Practical training will teach to evaluate the situation you’re in, and determine if you need to kick over. It will try to prepare you for that, but nothing short of a real situation can do so fully.
So, with all this said, yes, you can move between these.
Outlook isn’t a fixed thing, and you can change your approach in the moment. Knowledge of how people behave is critical for combat, but it is something that can be learned. Muscle memory can be a bit of a pain, but it’s not the end of the world. All martial arts are built (to some degree) around violence, and learning a new form of hand to hand is easier if you already have the fundamentals. Your muscle memory may mess with you in subtle ways, but it does come with the significant advantage of, “you already have it.”
Moving from one field to another is quite doable. It will take effort, and time, but if you already put the training in to learn one, you can do so again, it’s just a question of having the will to stick with it long enough to make it work.