Originally Posted by Primate
So much truth here.
I have trained with guys from all types of disciplines. A few in particular who come to mind are guys from traditional backgrounds who think that guy who train in combat sports are too inhibited to be effective. One guy in particular was a huge fan of Bruce Lee, had trained in a range of martial arts and spent a great deal of time in Wing Chun and JKD. I used to demolish him when we were boxing. Utterly demolish. He used to accept it, but always with a caveat, "it'd be different if we were kicking, because I'd low kick and do this or that..." etc. etc.
One day we put on some shin guards and I tore up his legs as well, most of the guys I train with tend to forget that I started out in kick boxing/muay thai because of how much time I've spent boxing. I think he managed to land one kick the whole time, and he ate a counter right hand in the process.
So all of a sudden it would be different if we were fighting properly because he could take me down, etc. So one day we're wearing mma gloves and going full contact. He ended up taking me down, and I locked in a guillotine. Oh, but it would be different on the street, because he could fight dirty.
Think about it. He could fight dirty by kicking me in the nuts, but he barely ever landed a kick. He could gouge my eyes or head butt me, but he never had his hands or his head in a position to do so. I certainly did, and I've become quite a fan of head butts in the clinch when properly used.
Now this is just one example from one guy, but I've got countless others. I've trained with guys from all kinds of backgrounds, some have destroyed me, some have been completely helpless from the moment we first made contact, others have been fairly competitive. This is across a range of sparring/fighting styles too, from straight up boxing to kickboxing, mma, straight grappling/wrestling or just throw a mouthguard in and go for it (think Geoff Thompsons animal day)
Overwhelmingly, the guys that destroyed me were from combat sports backgrounds (boxing, judo, muaythai, bjj), and just as overwhelmingly, the guys who had trained before that put up the least of a fight were from TMA backgrounds, including wing chun and JKD.