No, The Backholder Belt will not weaken your muscles the same way a lumbar corset brace would. A lumbar corset brace is designed to take over for your core, and if you wear it for too long, it makes your muscles weaker, putting you at more risk for injuring your back, getting a disk bulge, or a muscle strain.
The Backholder Belt doesn’t actually take over for any muscles, all it does is help to hold your SI Joints together, and therefore allow your ligaments to come back to their normal tension.
So you can wear it for weeks, or months without worrying about atrophy.