• Young man who developed back pain after lifting heavy equipment and who has paraspinal tenderness (muscles run along either side of spine) with negative straight-leg testing and no neurological symptoms, most consistent with muscle strain (most common cause of back pain in young otherwise healthy people)

So straight leg (Lesegue) test is very specific for sciatic nerve pathology. This dude actually gets to 80 degrees (is he a gymnast?) and remains negative for the test, so that's certainly not his pathology.

The main distracting answer here is herniated disc (which I chose), because herniated disc is the most common cause for a positive Lesegue sign (https://www.ncbi.nlm.nih.gov/books/NBK539717/).

I think the major differentiator here is the tenderness to palpation. I think this is a weak sign for raising suspicion of muscle strain over all the other pathologies listed though.