This article is from the Aerobics Fitness FAQ, by email@example.com (Robles) with numerous contributions by others.
Either ACE's Aerobic Instructor Certification or AFAA's Primary
Certification are excellent starting points for aerobics instructors,
and either organization's Personal Trainer Certification for Personal
There may also be other organizations in your area. In the northeast
(New Hampshire and Massachusetts) there is an organization called
Fitness Resources, based in Bow, New Hampshire. (Not to be confused
with Fitness Resources Associates in Needham, MA - another excellent
organization). Fitness Resources offers an aerobic instructor
certification program specifically targeted at new instructors that
is not terribly expensive (see How much does it cost?, below). There
may be other such organizations in your area.
Another consideration is the preferred certification in your area.
While both organizations are well-respected in the industry, some
clubs (and some geographic regions) prefer one or the other. If
you've got a specific place to teach in mind, find out who most of
their instructors are certified by.
Other organizations offer certifications at the national level. The
American College of Sports Medicine offers six different
certifications (three on the health and fitness track, three on the
clinical track), which range from Group Exercise Leader to Cardiac
Rehabilitation Director. The National Strength and Conditioning
Association offers Personal Trainer and Certified Strength and
Conditioning Specialist certifications.