In the words of Chris Haueter..."Think street train sport practice art".
I like this quote, but I'd like to expand a bit on how I interpret it in my own practice.
Finally, and this is the big one, it's important to note that no martial arts are actually designed for self defence. None of them. Zero. So, there's that.
That’s a pretty broad and definitive statement. I doubt it’s true.
depends on how you define self defense. Doesn't it? And we know there are a LOT of different definitions of that term.
Yeah, we can argue about this all day, but I'm going to suggest a working definition for this particular discussion. "Self-defense" can cover a lot of ground - lifestyle, threat awareness, avoidance, target hardening, de-escalation, escape and evasion, legal considerations ... and sometimes the application of physical violence. I'm going to suggest that when we bring up "self-defense" in the context of martial arts discussion then we are normally talking about the part where we deal with actual violence as it might come up in a scenario where we are protecting ourselves from a non-consensual physical attack. The other aspects of self-defense are not normally a major direct portion of martial arts training, although there can be significant indirect benefits for self-defense depending on how you train.
Fighting in a self-defense context has some important differences from consensual "street fighting", but there is also a large amount of overlap in the skills and physical and mental attributes necessary for each. Thinking that they are completely different is just as big a mistake as thinking they are the same thing.
Moving on to the original "sport vs traditional" argument ...
I'm not even going to attempt to define "traditional" in terms of martial arts. I haven't seen any attempt to distinguish "traditional" from "non-traditional" martial arts which is both internally consistent and widely accepted within the martial arts community. There's also no good way to clearly separate "sport" from "TMA". So I'm going to just focus on the value and limitations of "sport" training within the martial arts for those who want to develop the ability to fight in a non-sport setting (whether that setting is self-defense or some sort of consensual altercation).
1) I strongly believe that there is no way to develop reliable technical ability in any martial skill (punching, kicking, throwing, choking, joint locking, pinning, blocking, dodging, hitting someone with a stick, stabbing someone with a sword, whatever) without experience applying it against someone who is actively trying to prevent you from succeeding. This can be through real world application (fighting) or through live, resistive training (sparring). Note that sparring can come in a huge variety of forms depending on your objectives in terms of the specific skills and attributes you are trying to develop and the degree of safety you want to maintain while doing so. More on that a bit later.
2) Formalizing your sparring practice into some sort of official sport beyond the confines of your own training hall can have a number of benefits. One is that you can end up with a much larger talent pool of competitors who can push you to train harder and come up with technical innovations in the art. Another is that athletes have a high degree of motivation to win an official competition, as compared to regular sparring in the dojo. They'll train harder. They'll bring their "A" game and all their physical attributes to beat you, whereas in daily practice they might be focusing on exploring new techniques and not trying to overpower a weaker classmate with superior physicality. Competition also brings out more of an adrenaline dump and being able to deal with that is an important aspect of real fighting. Even those students who don't participate in the sport can benefit if their classmates do compete and become better sparring partners as a result.
3) Turning your sparring into a formal sport also has potential downsides. In every sport you have to have rules. (There are also rules in real fights, despite the protestations of the "no rules in da streetz" crowd, but I'll save that discussion for another post.) Competitors want to win, so they will inevitably start to tailor their practice into ways which work well under those rules but may be less beneficial or even harmful in a different context.
4) How do you gain the benefits of sportive competition without developing dangerously bad habits for a more combative context? There are a number of ways ...
5) You can start by structuring your sport rules in a way which you hope will reward the attributes, skills, and tactics which you are trying to develop for combative purposes. This will inevitably not work out as well as you would like, because someone will figure out how to exploit the rules in ways you hadn't thought of, but at least it can give you a good place to start and hopefully the sport can still help develop the goals you were aiming for even if some habits you don't like also get reinforced.
6) You compete under multiple rulesets, each of which is designed to reinforce skills and attributes you want to develop, but which have different weaknesses in terms of the "non-combative" behaviors they might engender. This way you can learn to turn off the "bad habits" when you are in a context where they aren't beneficial.
7) You can supplement your "sports rules sparring" in the training hall with drills and sparring methods which address the specific weaknesses in those rules. You can approach this in a lot of ways, but I'm particularly fond of asymmetric drills since you won't generally see those in sporting competition. For example, last week I put my students through a sparring drill where one defender started on the ground and two attackers (wearing MMA gloves) started standing. The attackers' goal was to stay on top and strike the defender. The defender's goal was to get back to his feet and make his way to a designated escape point while taking as little damage as possible. Doing this required the same skills the defender had been developing in one-on-one sparring, but obviously the scenario made it much harder to apply them.
8) Along the same lines as the previous two points, it's helpful to just regularly mix up your regular sparring with different scenarios and rules - grappling only, punching only, one partner grapples while the other punches, start standing, start on the ground, start on the ground with one partner trying to get up and the other trying to keep them down, use bare hands, use weapons, toss a training knife into the middle of an ongoing unarmed sparring match, allow hair pulling, allow groin kicks, start sparring inside a car, start sparring around obstacles, etc, etc. The point is that the practitioner can develop the mental flexibility to adjust their behavior to the requirements of the immediate context.