I also recommend karate. The style I'm involved with is Shotokan. Karate isn't for everybody, and Shotokan is even less for everybody. But I love it even though I'm not good at it -- my memory is terrible in general and worse still for physical movement. I always like to say I've killed more people dancing and during kata than during kumite (sparring). Attack when people least expect it. :) I love the sparring -- keeps the reflexes sharp. Less memory needed, because a jab to the face is a clear reminder to block.

Shotokan is very, very strict, and my sensei also. He'll give you a whack or put you on the floor doing push ups if your screw up. During breaks he's a pussy cat. Some people, a lot maybe, won't like it, but it's done wonders for me, and I see what it's doing for the kids that stick it out.

I'll be 68 in a week or so. I started 10 years ago, but there were breaks.

IMO, perhaps the least of the reasons to take karate is for self-defense. It's for health, discipline, reflexes, stretching, fun, sociability. The chances of your ever using it for self-defense are extremely slim, and the idea of wanting to use it outside the dojo is very dangerous. When we spar the adrenaline is high, the alertness is high, but there is zero hostility or aggression. When either of you gets a good shot in, you're both happy.

But never mind -- karate or whatever -- yes, exercise is very good for body, mind and soul -- though not the sole, it wears out. Hiking and just walking are also great.