I just wanted to say that I do experience the same!
Most of te time its more obvious, but for example: I always get droopy eyes ater phone calles (plus my whole face is weak)
or not being able to chew after walking too much.

I explained it to my family like this: Your cell phone or laptop has a rechargable battery with a limited "life" - when you have used up all of the available energy, you have to recharge that battery before your device can work again.

Let that battery run completely down, and you have to wait a LOOONG time before you can re-use your equipment (not necessarily true nowadays, but that is how it used to be). Sometimes you have to re-load all of your information back into your device if you screw it up too much. And in the worst case, you have to buy a new device because the old one isn't salvageable.

Unfortunately, you can't "buy" a new body, so if you get to that point, you're....well, dead.

With laptops and cell phones, the more you task them with, the sooner they run out of juice. If you know that your battery is running low, you refrain from doing things that you know will completely drain power from your device - you only use it for the things you deem critical/necessary, and you hold off on doing extra stuff until you have a chance to get a full charge again.

Same thing with an MGer's muscles - our "batteries" run low pretty quickly, so we have to know the signs so that we aren't ever in danger of running out of juice. We learn to plan accordingly, and we figure out pretty quickly what tasks are "critical" and which ones can go by the wayside.

For people with MG, "exercise" pulls an awful lot of juice - so much so that we generally end up TIREDER after exercise than people without MG. Which if you think about it, makes an awful lot of sense. "Normal" people are able to pull in all of the AChE that they need - we aren't. Our muscles don't get enough juice, so they "fail" earlier.

Are you taking your walks to try and boost your energy? If so, you are probably finding that you have LESS energy after your walks, and it takes you longer to recover. The physical symptoms that you describe tell me that you are doing too much.

There is nothing "physically" wrong with your muscles, it's the RECEPTORS which draw in the AChE that are the problem. "Building up" your muscles isn't going to do anything to fix the receptors. You can have the strongest, tautest muscles in the world, but if that chemical isn't able to get to them, those muscles are going to be useless.

(By the same token, you can have a full tank of gas in your car and a brand new engine, but if the gas can't get to the engine, the car isn't going to run)

You're going to have to decide what your priorities - in terms of physical activity - are. Which is more important, teaching or going for a walk?

Instead of a stool (you'd be amazed at how much energy it takes to hold your head and neck upright), you may find that you are less fatigued in a chair that has a high back and which reclines. You might also need something to rest your feet on, to take pressure off of your leg muscles as well.

You may want to look into a "zero gravity" chair for teaching your classes - just explain to your students (and parents, faculty, etc) the physical need for it. Most people are very understanding.

The less stress that you can put on your muscles, the longer you are going to be able to do things without wearing yourself out.

Hope this helps!