If I am under a doctors note with specific restrictions for lifting heavy things and I am injured because the manager refused to provide lighter duty jobs during my shift, can I be fired? Is there any legal recourse I can take?
Thank you for any help

Was the injury work-related? Generally speaking, employers are not required to provide light-duty jobs for non-work related injuries (and, in some cases, not even then) if there are none available. Have you discussed this with Human Resources, especially, did you do so before you returned to work?