Start With National Certification
Certification from a nationally recognized certifying organization is the first thing to look for. It's your assurance that you're working with a group fitness instructor who has the knowledge to provide you with a safe and effective workout.
Certification is more than a piece of paper. For example, the American Council on Exercise (ACE), which is the largest non-profit fitness-certifying organization in the world, requires group fitness instructors to pass an intensive three-and-a-half hour, 175-question exam that covers exercise science and programming knowledge, including anatomy, kinesiology, health screening, basic nutrition and instructional methods.
After checking certification, there are a few other things you should take into consideration when choosing an group fitness instructor. Here's a guide: