I can't let the kids outdo the old man, so I have begun Tang Soo Do, a traditional form of Korean karate.  man whatta workout.  I will keep this updated.  Ops

Good deal! I'm not the only one. I'm late 40's and just started Hapkido, its good stuff. It's also of South Korean origin. If you have any history of knee problems, I recommend wearing those neoprene knee supports. I wear a pair under my dobok and the extra support is nice when doing lots of kicking.

A few observations from my first couple of classes:

The women are FAST.  

High belt little kids are very small fast movers.

No high techniques, too hard on the neck and shoulders.

Sparring is one hell of a workout.  

I really like this, although I am finding muscles that I forgot I had...    Ops

High kicks are cool looking, but as a wise man in my dojang said...if you want to kick somebody in the head, kick them in the shin first.

However, stretching is vital to these activities, every day if possible.

Did ya know that Chuck Norris is the "poster boy" of Tang Soo Do...he's known for karate but is actually a Tang Soo Do guy.

As far as age goes, there is a married couple in our dojang that are both black belts and started training at age 50.

Beware, I can't speak for other martial arts, but Korean martial arts will reel you in and you won't want to quit. At least if you are in a good school. I think it's one of the best things I've ever done for myself.