Debbie,
What you describe is pretty much how this body's symptoms go as well. Things are worse toward the end of the day, but during and right after exercise things seems to be better...then first the weakness, then the spasms set in.

Getting exercise on recumbent or even regular bikes are out for me because they irritate my lower back discs; although I can still ride a regular bike for pleasure when balance issues aren't a problem. I try not to become depressed over the fact that I used mountain bike regularly and even competed in equestrian sports (3-day eventing, cutting and endurance racing) just a few years ago.

Three discs in my lower back have varying levels of prolapse and two have been herniated, and 3 in my neck are also prolapsed now...all from falls due to MS. This makes exercise of the para spinal muscles absolutely necessary to keep the supporting musculature of the spine as strong as possible. I really don't want to have surgery; although that was recommended a couple of years ago.

I get some back exercise from my work as a massage therapist and through walking, gardening etc, but since my participation in those things has been on a steady decline because of MS fatigue and other symptoms, I use a cross country ski machine to round things out and to get some cardio in the relative safety of the indoors.

The treadmills and elliptical trainers tend to irritate my legs and I think that it is because full extension of the knees and hips doesn't happen with them. The cross country ski machine allows for more full extension of the knee, nearly full flexion and extension of the ankle and more full range of motion of the hips as well.
I bought my second hand Nordic-track for $25.00 through the want ads a few years ago and I often see them up for sale for around the same price, where they can run in the hundreds of dollars new .

With love, Erika