working out regularly, eating well, and sleeping well. That’s what keep you fit and in shape. That’s it. working a manual labor job gets you the excersize part, you gotta do it properly but that task is fullfilled by having a manual labor job. You still need to eat and sleep well and not get addicted to painkillers (that can happen to anyone). An office job fulfills non of the tasks required to be fit. Sure less chance of injury since you’re in an temp controlled cubicle. Much higher chance of being unfit though.