I attended two Mary Wanless clinics several years ago and she suggested
that we use the Callenetics exercise program for riding strength. The book is
called "Callanetics Countdown - 30 Days to a Beautiful Body", By Callan
Pinckney. It may be out of print, but if you can find that book I guarantee you
will be a different person after 30 days. She has a work out designed for each
day and if you follow it, you will have tremendous strength and will lose inches
but probably not lose weight.
Toward the end of 30 days, you are doing 400 sit-up type exercises (100
times in each of four positions) plus other strength building exercises. My
neighbor and I did the 30-day workout and it made a BIG difference in our riding
abilities. We were the oldest students in our dressage class, but we put the
young gals to shame with our strength and stamina.