I'm gonna have to disagree with the thought that a tripod or image stabilization is simply unnecessary. Of course it depends on what you are doing. If you are walking around taking pictures of people then a 50mm lens and 1/60 second shutter will be fine if your hands are steady and your technique good. However, if you are shooting a match from one of the stands, and so you are further away, then you'll be using a much longer focal length. For a 135mm on a camera like a 450d, you'd probably want to have your camera set to 1/250 or something of that sort. Gym lighting often won't allow for that. Image stabilization generally buys you 1-2 stops, so you can probably get away with 1/90s. That's too slow to freeze movement but at least you won't spoil a shot of people standing in kamae because of unsteady hands. A tripod or a monopod is another way and the issue of it getting in other people's way is overstated, I think. If you are shooting a match, you probably won't actually be walking around the shiaijo that much. For one, are you really going to be cutting in and out and around the crowd to get in position even without a tripod? Second you're taking a big chance that you won't be in position to shoot when the action happens. More likely you'll find a good spot, set up, and you'll be more or less standing there waiting for the opportunity.