I'm not sure about your exact position in company, but there are some cases when boss askedasks his employee to move something, he doesis not really asking him to roll up his sleeves and do it, but to organize and manage the process during this thing is done.
Use his authority to ask other employees to help you with this task. Later after you complete the task, you can tell your boss about your medical condition, and who helphelped you movingmove things.