It depends on the class
I offer two different bootcamps: one I participate in and the other I do not.
It is not “expected” at all
The most important aspect to teaching a class is teaching a class well: providing safety cues, proper progression, anticipation of what comes next, and the ability to pace depending on your participants needs and fitness level.
I am both a group fitness instructor and a personal trainer. I teach various fitness classes as well as small group classes. Everyone may be different, but this is what I do:
Group Fitness Classes– I always lead and participate at the same time. Most of my classes are to music (on the beat), and participants can follow me better when I participate. However, I keep a close eye on everyone while I participate and constantly watch form. I’ve been teaching so long that it is second nature to me to teach, monitor form, and correct it if needed. I will also walk around the class sometimes.
Small group fitness classes–I teach bootcamps and TRX. These classes have music, but they are not to the beat. For Bootcamp, I may warm up with them and demonstrate the exercises, but they do the class and I walk around and watch form as well as time them. This is one of my more intense classes, and I am there to show them the exercises and make sure they are doing them correctly. For TRX, I tend to do a little of both. Again, participants need to know proper form, and it is easier if they watch me do it first. I walk around this class to watch form and correct it.
For small group training, my feeling is that you are there to guide and instruct, not necessarily participate. You will probably get different opinions on this one, but that’s how I do it!