For martial artists and boxers who fight bare knuckled, conditioning your knuckles can be a very important part of training. Hardening and toughening the knuckles can help prevent serious injury to the hands. You can harden your knuckles in three different ways: push ups, punching, and knuckle-walking.
Find a soft surface such as carpet or grass. The area must be big enough to stretch your body out.
Put your body in push up position. To get into push up position, lie chest-down with your hands flat at shoulder level and your toes bent over your feet so that the balls of your foot are touching the surface. Straighten your arms so that the body is in a straight plank position.
Move your hands from a flat position to a knuckle position. Curl each of your fingers underneath your hands toward the palm so that your upper body weight is rests on the knuckles.
Do a few sets of push-ups 10 to 20 repetitions per set. Do as many sets as you feel you can, but pay attention to how your hands are feeling. If your knuckles are particularly painful, do not continue the exercise until they have had a couple of days to rest.
Work your way to harder surfaces such as tile, marble or wood floors as you get used to knuckle push-ups. When your hands start to become less sore after knuckle push-ups on soft surfaces, try a short set or two on a hard surface and see how your hands feel. Slowly work your way to doing all of your sets and reps on a hard surface.
Keep careful track of your progress so you'll know how much to push yourself. You will want to continually but slowly increase the strength of the surface to improve bone density in the knuckles, but doing too much too quickly can result in knuckle fractures.
Layer two telephone books over a thick wooden board.
Slap your hand on the telephone books first with your palms, then with the back of your hand lightly for five minutes a day.
Add intensity when you feel your hands are getting used to the light slapping. They should become less and less sore after sessions.
Remove, eventually, a phone book from the board and then remove both phone books from the board. Once you move to the board, you can also use trees during these slapping sessions.
Find a partner that is strong enough to lift your lower body.
Have your partner hold your feet and walk behind you as you walk on your fists. Start out with a couple of minutes a day, two or three times a week, and work your way up as your knuckles cease to be sore after sessions.
Start on a soft surface such as grass or carpet and work your way up to harder surfaces such as concrete or marble.