Do you have a doctors certificate? And is your personnel management aware? You are allowed to refuse unreasonable requests. If you physically can't do it, they cannot force you to do so. Although, if they are aware, and still force you to do so, if you injure it anymore, you could go all American and sue them...I work in a special needs school but I injured my back limiting the things I can do, they are forcing me Into a position were I will be forced to do things wich will hurt my back