A visit to a health club, park district, or YMCA aerobics class is a good way to observe the work of fitness trainers and aerobics instructors. Part-time or summer jobs are sometimes available for high school students in these facilities. It may also be possible to volunteer in a senior citizen center where aerobics classes are offered. If possible, enroll in an aerobics class or train with a fitness trainer to experience firsthand what their jobs entail and to see what makes a good instructor.

Aerobics instructor workshops are taught to help prospective instructors gain experience. These are usually offered in adult education courses at such places as the YMCA. Unpaid apprenticeships are also a good way for future instructors to obtain supervised experience before teaching classes on their own. The facility may allow prospective aerobics instructors to take their training class for free if there is a possibility that they will work there in the future.

Opportunities for student fitness trainers are available in schools with fitness trainers on staff. This is an excellent way for students to observe and assist a professional fitness trainer on an ongoing basis.

Three general levels of aerobics classes are recognized today: low impact, moderate, and high intensity. A typical class starts with warm-up exercises (slow stretching movements to loosen up muscles), followed by 35 to 40 minutes of nonstop activity to raise the heart rate, then ends with a cool-down period of stretching and slower movements. Instructors teach class members to monitor their heart rates and listen to their bodies for signs of personal progress.

Aerobics instructors prepare activities prior to their classes. They choose exercises to work different muscles and music to accompany these movements during each phase of the program. Generally, instructors use upbeat music for the more intense exercise portion and more soothing music for the cool-down period. Instructors demonstrate each step of a sequence until the class can follow along. Additional sequences are added continuously as the class progresses, making up a longer routine that is set to music. Most classes are structured so that new participants can start any given class. The instructor either faces the rest of the room or faces a mirror in order to observe class progress and ensure that participants do exercises correctly. Many aerobics instructors also lead toning and shaping classes. In these classes, the emphasis is not on aerobic activity but on working particular areas of the body. An instructor begins the class with a brief aerobic period followed by stretching and weight-bearing exercises that loosen and work major muscle groups.

In a health club, fitness trainers evaluate their clients' fitness level with physical examinations and fitness tests. Using various pieces of testing equipment, they determine such things as percentage of body fat and optimal heart and pulse rates. Clients fill out questionnaires about their medical background, general fitness level, and fitness goals. Fitness trainers use this information to design a customized workout plan using weights and other exercise options such as swimming and running to help clients meet these goals. Trainers also advise clients on weight control, diet, and general health. Some fitness trainers also work at the client's home or office. This convenient way of staying physically fit meets the needs of many busy, active adults today.

To start a client's exercise program, the trainer often demonstrates the proper use of weight-lifting equipment to reduce the chance of injury, especially if the client is a beginner. As the client uses the equipment, the trainer observes and corrects any problems before injury occurs. Preventing injury is extremely important. It is good idea for trainers to carry liability insurance to protect themselves should anything beyond their control happen with a client.

Fitness trainers also use exercise tape to wrap weak or injured hands, feet, or other parts of the body. The heavy-duty tape helps strengthen and position the joint to prevent further injury or strain. Fitness trainers also help athletes with therapy or rehabilitation, using special braces or other equipment to support or protect the injured part until it heals. Trainers ensure that the athlete does not overuse a weak joint or muscle, risking further damage.