Question 051: Hand toughening

I am very enthusiastic about martial arts and it has become a hobby, a sport, and a -do, a way of life. But although martial arts have become a way of life for me, it is not my whole life. I am a teenager who is currently working diligently in school and putting a lot of effort and struggle into getting decent grades. I acknowledge that martial arts have become a big part of my life, but I also know that I am at an age when I must work hard for college applications. I put a lot of effort in my karate training, but as of now I seek martial arts as a way of keeping my physique and spirits up, not as a profession. Because of that, I am not willing to go to extremes to toughen up my hands. Is there a way to strengthen and make knuckles bigger without traumatizing them? If not, perhaps there a safer way of using Wolf's law?