Not at all - those are legitimate branches of the martial arts. Kendo counts as a martial art because it is specifically designed to utilize the weapon as an extension of one's body - you train in kendo just as you would train in judo or karate. But there is no type of martial arts, that I know of, which utilizes a flying shield or bat-shaped boomerangs. If anything, Cap's use of the shield exhibits more of the talents of, say, an expert pool player than a martial artist - and while Batman is very good at throwing those Batarangs, he's basically just throwing boomerangs in an accurate fashion - a talent your average 12-year old can master. In both cases, it's a skillful use of a weapon, but it's not the same sort of skills that a martial artist uses when he uses, say, a sword or a pair of nunchucks.