Can I retired with my medical and pension benefits?

My supervisor was ready to retired,one day she told me I had it go do a job that I haven't done it for ten years. I try to tell her that I wasn't able to handle that kind of job. She told me that job is part of my job duties,like a good worker I did the job that cause my injured to my back. How? I got on a back of a food truck to deliver hot food cars that weight approximately 300 pounds. The jumping,pulling and pushing hurt my lower back.