• Bullying. Martial arts training won't turn a child into a bully, but it's best avoided if your child is already a bully. Martial arts teachers instruct children when not to use their training; bullies have already crossed that line. If you know or suspect that your child bullies other children, martial arts training will frustrate him to tears — or make him a better bully. Instead, seek professional counseling if you believe the problem is serious.

• Serious family dysfunction. As I said before, one of the most enjoyable benefits of martial arts for Sam and me is how it has strengthened our relationship. I doubt it would be as beneficial in a family with serious problems — impending divorce, rebellion, an out-of-control teen and so on. A martial arts school is not a military school; don't be tempted to use one to straighten out a troubled child or to set a troubled marriage on course. Again, seek professional counseling instead.

• No quality schools. If there are no martial arts schools in your area, don't try to become a martial artist with videos, books or mail-order courses; you'll just frustrate yourself and waste money. Similarly, if the only schools in your area are of poor quality, avoid them. Martial arts can be a great family activity, but don't settle for a bad school. Best to pursue another sport or pastime with your children.

— Greg Hartman