Michael Gallagher wrote:
Slow is better for learning and training safely. My Kali instructor, who also has permission to teach Pentjak Silat Serak, drives this point home constantly. According to him, there's a large body of research to back this up. Thai Boxers, I understand, also spar at a compartively slow pace; there's no way they could do that all day in a hot and humid country and live to talk about it if they didn't. Of course, when they go in the ring, they're full speed ahead, but that's the payoff for going slow.
One reason it's a good idea is as follow: When you go dull speed ahead, your fight-or-flight refelx can kick in, resulting in an "adrenaline bomb" being dumped into your blood stream. So you "dumb down" to moves that don't have a lot of fine motor control. This is why in Karate-Do, kumite doesn't look like kata, bunkai, or ippon kumite -- they're going too fast to have presence of mind to do those beautiful techniques! Of course, there may be perfectly valid reasons why they go full boar out the gate, either from the perspective of attaining mushin no shin or some aspect of Japanese culture. But it has that drawback.
Now, once you get used to doing things slow, of course, then you can ramp it up, from say 1/4 speed to 1/2 and so forth. But it shouldn't feel any different -- just take less time. That's also what my Kali instructor is doing -- sheparding us through ascending levels of "practice sparring" before you get to the real deal.
So in a nutshell, slow is better. And it's best of your sensei agrees with you; otherwise, it's a moot point.
Working slower gives one time to realize what he is doing, and make sure everything is done exactly as it should. One should practice more at slower speeds, learning. And practice faster only occasionally, to maintain his ability to accelerate the same movement.
The only issue that should be tested at fast speed is timing, and even then, a great M.A. can be identified as those who seem to move slower than their attacker (good timing and positioning requires less movement).