I work at Disneyland. Is this discrimination against my size?

I've worked at Disneyland off and on since 2008. I was in day custodial for an accumulative 8 years. I got put in another department when I was hired back and I just want to transfer back to custodial but they now have a POET. A physical exam that requires you to perform certain tasks at an offsite medical office. The exam includes some tasks that should not be required for everyone. I am 5'2 and almost 110 lbs, I have no physical restrictions and am in pretty decent shape. I swim everyday and work out regularly but yet I cannot lift a 50lb bag out of a trashcan that is half my height. I can lift it up but I cannot lift it above my waste in front of me. That alone is the reason I cannot be placed back in day custodial. This test makes no sense. I worked so well in custodial in the past that I was promoted to Trainer and to Working Lead. There is no reason I cannot perform the actual on the job work. I need help.