Cramps

[H2Andy]

here's a video that will illustrate the frog kick (among others) far better than i can explain it:

http://www.gue.com/classroom/propulsion/index.shtml

 

[diver_paula]

In addition to the above suggestions, I am practically the same age and I found that the type & weight of my fins have a big influence on the frequency I get cramps.
When I use a hinging fin like Mares Volo or Dacor Panther I very rarely get cramps.
If I use a rigid heavy fin then I get them frequently.

I'll second that. With flexible fins my legs feel fetter at night.

Paula