Rock-hard knuckles make your punches strong and prevent injury. Wolff's law -- pressure on bones makes them adapt and become stronger -- means that boxing training can lead to hand hardening, if you do it the right way. Work on hand conditioning as a regular part of your boxing or martial arts workout. It may keep you from a sidelining injury, such as boxer's knuckle or broken bones.
Punch into a bucket filled with rice and grab and twist the rice in your hand. Add a clockwise or counterclockwise twist to the movement to work your wrists. Do 10 reps on each hand two to four times a week. This rice grip technique conditions the knuckles and develops the hand and wrist.
Perform pushups, as usual, but put your weight on the first two knuckles of each hand. Only use your thumbs if you need stability. Do pushup sets like this to 80 percent of your capacity two to four times a week.
Punch the heavy bag wearing only your wraps. Working out with the heavy bag is a typical part of boxing and martial arts. Make hitting this bag part of your hand-conditioning. Follow your typical bag-training routine -- always using proper punching technique, distance and stance -- but leave off the heavy gloves. This increases the pressure on your hand bones, allowing your hands to strengthen and harden according to Wolff's law.