To Sit or Not to Sit - this is a question for both the participant and the instructor in Adaptive Aerobics. While some athletes have no choice, being confined to wheelchairs or having mobility limitations that impair balance or coordination, those athletes able to stand in an aerobics or step class should be encouraged to do so. Even if they cannot perform all the movements or if they cannot use the step, the fact that they can use the large muscle mass in the lower extremities to generate oxygen demand means that they will achieve a training effect much more easily than just using their upper body muscles. This is appropriate when integrating disabled athletes into the general population health club classes. For example, if a prosthesis limits the ability of an athlete to perform a pivot turn step on the bench, demonstrate an alternative step sequence that moves and turns the athlete's orientation identically as your pivot turn step does in the same number of beats. You will find that the disabled athlete is not the only participant in your class who uses this alternative step sequence!
You, the aerobics instructor, when faced with a class of both seated and standing athletes, or when programming a class of exclusively seated athletes, are faced with the question of whether to teach from a seated or a standing position. There are adaptive aerobics videos that feature standing instructors and seated participants. I personally recommend that, when teaching a standing class, the instructor should stand and when teaching a seated class, the instructor should be seated. The problem in teaching a class with both standing and seated participants from one position or the other is communicating with the class what movements are primary and what movements are suggested adaptive movements. This is a similar problem in teaching a standing class with varying levels of fitness; when you demonstrate a low-impact alternative to a high-energy movement and the entire class follows you, even the aerobics monsters who don't need the alternative.
One suggestion for the combined classes is to team-teach. Several combinations of instruction can be used, the most common being both instructors at the from of the studio and one instructor demonstrating the standing aerobics, while the other is seated, demonstrating the adaptive movements. For a class with all standing participants, but with some balance-impaired or coordination-impaired, one instructor could teach the basic class, while the other demonstrates suggested modifications. Another combination would have one instructor in front of the studio with the other a "roving" instructor.
Again, I recommend that, when teaching an exclusively seated class, the instructor also be seated. This does not put a barrier between the class and the instructor. Also, the instructor is reminded that certain movements just can't be accomplished from a seated position. I also face the class, but this is partly because the classes I teach seated are not in mirrored aerobics studios and I can't watch the class in the mirrors. This allows me to immediately identify anyone having problems with mastering any movement so that I can introduce a modification within the class sequence. It also directly communicates the proper form, since many of the movements are performed in front of you body and would be hidden if my back was presented to the class.