Fitness instructors belong to skill-based industries, especially practical skills, which are very important. In the early stage, fitness coaches should start learning from basic theoretical knowledge, such as sports nutrition, sports anatomy, sports physiology and so on. But there are more practical skills, from the use of basic fixed equipment to the use of free equipment, as well as relaxation and stretching after exercise, which are the basic skills that fitness coaches must master; Advanced core skills to be learned in the later stage include functional training and sports rehabilitation skills, various small equipment training, improving physical fitness, and sports rehabilitation training for special people.

If girls want to be fitness instructors, most of them also study these contents. As for the difficulty, it depends on the individual. It might be easier if you exercise harder. If you are usually an inactive person, then the early stage may be harder.

I hope my answer is helpful to you.