When you knock someone down press L1+L2+R1+R2+X at the same time, and keep hitting them. You should regain some of your energy.

Fight with big heads:
At the main menu press left and circle, left and triangle, left and square, left and x. A bell will sound if done correctly (This only works with created boxers).

While fighting in career mode I found a way to always win no matter what. This isn`t a code but a flawless strategy. You must, however, knock the person down. At almost the same exact time as you knock the person out you press start and throw in the towel. Don`t worry, if you pressed start at the correct time the game will, instead of saying you threw in the towel, it will believe that the computer character threw in the towel. It will continue the count down, but at the end it will say that you won by TKO.

Press left & square at the same time, press left & triangle at the same time, press left & circle at the same time, then press left & x at the same time. Every time you press left a the button you should hear a bell after you do all four you should hear a swoosh sound.

When you go to train your guy, pick the speed bag, or heavy bag and go into the match. Then, throw in the towel so it brings you back to the menu where you can choose the speed bag or the heavy bag. Keep repeating this process till everything is 99!

When making a boxer in "career mode" type in the name PSIRULES fight one match with him, then exit out of career mode. When you go back in to your career your man will be 7'5 and his power, strength, ans speed will all be 100