Hiya

If you were wearing tighter garments that supported your back muscles, then I suppose as you aren't getting that support from the looser garment, then it could cause you to have a back ache..... you need to strengthen your back muscles so you don't depend on supportive briefs !!
Hope this helps !!??

Hello Boxerbriefsnot,

I am not a doctor, however, I would find it unlikely that just changing the type of briefs you wear would cause your back pain.

The only why to get the proper answer is to seek the advice of a medical professional such as a neurologist and/or doctor specializing in back pain.