What would you do if your responsibilities at work radically changed out of the blue? You weren’t promoted or demoted--you were just suddenly expected to complete tasks totally unrelated to your job.

“At one time in my career, I was in a retail management training program and about two weeks into the program I was pulled out and asked to staff a human resources office in one of the stores,” says Dr. Katharine Brooks, director of Liberal Arts Career Services at The University of Texas at Austin and author of You Majored in What? Mapping Your Path from Chaos to Career. “I kept the management trainee title and pay for six months but my duties were completely different from the other management trainees—and from what I had expected to be doing.”

It’s not common, but it does happen, says Connie Thanasoulis-Cerrachio, a career expert and co-founder of SixFigureStart, a career coaching firm.

“This happened more frequently during the recession because companies were faced with an economic crisis that hadn't been seen since the Great Depression,” says Al Coleman, Jr., author of Secrets to Success: The Definitive Career Development Guide for New and First Generation Professionals. “Employees were being asked to take on more responsibilities to help companies grow or maintain market share. Employees also saw an increase in responsibilities due to the significant reductions in force, which lead to retained employees sharing or assuming the responsibilities of their displaced colleagues.”

Why is it still happening? In today's economy companies need to adapt quickly to changing needs in the marketplace, Coleman says. “Such a rapid change at the corporate level will inevitably affect an employee's role and responsibilities, and may likely come without a formal promotion or demotion in the scope of your duties.”

Your employer might also drastically change your role without an official promotion or demotion because “those can cost the company in money in morale if they are done poorly,” says Debra Benton, an executive coach and author of The Virtual Executive: How to Act Like a CEO Online and Offline. “Managers will often give a trial job to someone to test the employee’s capabilities before promoting him. Likewise, your manager might give you a test challenge to reconfirm her decision to demote or fire you. The test works better for them in both directions.”

When an employee has to suddenly take on a different role at work, the implications depend on whether or not they are taking on more or less responsibilities, says Andy Teach, a corporate veteran and author of From Graduation to Corporation: The Practical Guide to Climbing the Corporate Ladder One Rung at a Time. “If it's more responsibilities and it's without a promotion, it will usually mean working longer hours and becoming more stressed which will lead to some resentment by the employee toward the employer.” After all, who wants to take on additional responsibilities without getting the promotion and raise that deservedly should be part of the overall package?

“I think the main reason an employer would do this is financial hardship,” he says. “This situation usually occurs after a co-worker or co-workers are laid off to save money so the employees who are left have to pick up the slack. Since the primary reason for doing this is usually a loss in revenue and profits, the employer does not have the money available to reward the employees who are doing more with less, which is unfortunate,” Teach adds. The hope is that once there is a financial turnaround, the company will somehow reward those employees who are currently not being recognized for taking on additional responsibilities, he says.

In Pictures: What To Do When They Radically Change Your Job