What is worse? Do you have pain? As I said, after I do the leg press I have to be careful getting off the machine because my muscles are tired. I then go do some upper body workout and within a few minutes my legs are okay (for me - maybe not for someone who does not have MS). I guarantee you, I do not jump off the leg press machine like some do.
Today, playing golf my left leg got tired - it was not striding very well even with the WalkAide. But, after sitting down, getting something to drink and resting for a few minutes, I was good to go.
Really, Chris, ask your PT to help you with some breathing exercises. I think you will see a big difference. And, if you go to Stanford the breathing will help to get you clearer MRV images.