Good for you LP!
I just ordered Jillian Michael's Killer Buns and Thighs and Abs DVDs. It's getting harder to drive to the gym 3-4 times a week. Now that I am happy with my weight, I really need to tone up.
Running up hills creates killer buns and thighs at the same time. Push-ups creates killer abs.
I allowed myself to be talked into doing calisthenics with a fellow sailor, back in my early thirties. He was conditioning himself to try out for the Navy Seals. We were stationed on the same ship. At that time, I could do sit-ups and crunches endlessly, literally. But his routine included lots of push-ups, 2 sets of 25 in the morning, 2 sets at noon, and 2 sets after our shift ended. On that third group of sets, on my 1rst day trying to keep up with my friend, I pulled a stomach muscle. That ended that.
If you do 1 set of twenty push-ups per day, you will be amazed at the workout you give your core muscles. It takes a great deal of stomach muscle strength to keep your body in a straight line while doing push-ups. It doesn't hurt the pectorals, triceps, or deltoids either.
Another great stomach exerciser is swimming, especially the dolphin kick, though the Australian crawl is pretty good at working all of the muscle groups as well. The butterfly, well that's for people in much, much better shape than me.
And you have to be careful with the butterfly, because it can over develop the pectorals and lats, while leaving the back muscles untested. People who specialize in the butterfly have to do back exercises to avoid becoming muscularly unbalanced, witch can lead to health issues.
Good luck with your conditioning program, whatever it is.
Seeeeeya; Chief Longwind of the North