Sometimes it's awkward or difficult to bring up additional compensation with your boss, also known as your Program Director or Assistant Program Director.  Sometimes it's because you're caught off guard by the request, but more often than not it's because the practice of medicine is supposed to be an altruistic profession and for trainees, you don't want the PD or APD to perceive you unfavorably.  Saying 'no' can be tricky.

First off, additional compensation is a very good thing, indeed!  That's why the union has (for nearly 50 years) protected your right to moonlight and added language for additional supplemental payments.. 

If you're putting in additional time working for free at Michigan Medicine, going above and beyond the scope of your training, that's time being spent that you could be moonlighting and getting paid from another employer.  Even if you don't end up moonlighting, you can always use that as an excuse.  "I plan to moonlight and can't make any additional commitments." 

Always ask if the additional work or assignment comes with additional pay.  If the answer is no, simply say, "I don't have the bandwidth to take more on."  You cannot be forced to engage in activities unrelated to your training.  

If you are part of a smaller fellowship and aren't eligible for a GME funded chief resident stipend, your program can still pay you to assume that responsibility.  If they refuse, you are under zero obligation to assume any non-educational role within your program, such as coordinating work schedules, Grand Rounds, or other administrative tasks.  Be clear, tasks not associated with your job description are tasks someone else should be doing.

When trainees are continually asked to overextend themselves they begin to feel anger and resentment towards their employer and that leads to additional frustration and burnout. You can always say, "I'm a great advocate for my patients, and I need to advocate for myself on this.  My answer is no, but thank you for thinking of me."