Supposed to be good for cardio, and the conversion of fat into energy. I've read you should take it prior to workout. You can get it in liquid form.. Thing is, there is only circumstantial evidence that it actually works. I take it with an hGH support supplement. If you are trying to lose weight, they say it is good to stack with a good fat loss supplement, like lipo 6. Basically, take the liquid form 15-20 prior to cardio.
L-Carnitine is good for helping to burn fat, I don't think there would be any reason for a boxer NOT to take it. You can get it seperately or in a complete energy/fat loss supplement like Thermadrol