Recently I hurt my back, and at a Club competition I wore an elastic back support. I was told it was illegal to use it without a medical certificate. the range officer pointed out that under the ISSF rules it was not permitted.
I wonder why women, who wear bras, are allowed them! Are they not supports?! :)) (sorry, but I must duck for cover!!!!!)
It's in the "spirit" of the rule. A bra, for a female is within the "spirit" of the rule, while a back support, wrist support, tendonitis bands, over-the-ankle boots, for either gender, are not in the "spirit" of the rule.
Wear it. You just can't shoot for record.
Hope your back gets better.