When you’ve gotten far enough along in your medical care that you can safely perform some work, your physician will provide a partial return-to-work release. You can return to work at this point, but there may be certain restrictions.
Restrictions may limit the number of hours you can work during a day or week. Restrictions may limit the amount of weight you can lift, or they may limit the amount of driving, standing, sitting, stooping, kneeling, etc. Your employer may call these restrictions by the common phrase “light duty.” As a general matter, if your employer offers a light-duty job that is within your doctor’s medical restrictions, you’ll need to do it or risk termination of benefits and employment.
If you genuinely feel you won’t be able to do the job that is offered, you will need to get a supporting medical opinion. You have the burden of proof, so you will need your provider to write a report. Your provider’s report will need to demonstrate why it is not safe for you to perform the specific tasks of the specific light duty offered.