I also shadowbox, and at least for me, forms training is not an equivalent of shadowboxing with the same intent and same objective. Some people who train heavily in kata for the bunkai (applications, typically interpreted as hidden applications) side of things is going to heavily disagree with this, but for me, I train in forms for the same reason that US Marines learn to spin rifles. In addition to the biomechanical lessons about basic movement that it reinforces (Fish of Doom touched on this), it's a challenging drill of precision, crispness, and sequence, that ultimately leads to a performance art I really enjoy. I enjoy practicing, I enjoy performing, and I enjoy competing in, because forms competition is a competition category just like sparring competition is, at least in the style I train. Yes, there's some crossover benefit to my sparring training, but there's more to it than that, and if all I was trying to do was improve sparring, there are other things I could do that are probably hour-for-hour more efficient. For those who aren't familiar with what I mean by "spinning a rifle," here's the basics: Here's what happens when people get really good at this practice: It's not hour-for-hour the best way to learn to fight insurgents in Fallujah. Obviously. But it's a drill of precision, focus, and performance that's been part of the Marines for generations.