Wow! I should have been keeping up with this thread! Ric B. is getting a fitness cert! How cool is that? As one who has taken infinitely more education in that industry than I need, and as one who also trains the trainers, I can comment on Ric's analogy.
Awhile back, when Nolo had her Hyperchange forum, I recall my first post on a topic similar to this one. Unlike the ski instruction industry, there are many certification routes that potential fitness instructors can embark upon. Some carry more prestige than others. Some are extremely expensive and time consuming. Some are suspicously inexpensive and short. Further complicating matters, different certs will be more appropriate for different for different instructional populations.
ASCM is the most clinical, with knowledge requirements close to the level of medical practitioners. Someone who is new to the industry may have a hard time passing the exam. But if a trainer wanted to work with "high risk" clients, this certification is a must. However, even though ACSM is considered the "Gold Standard" in certification, some fitness centers, such as the one at MIT, will not accept it, since they believe its too clinical.
If someone is interested in traditional weight and equipment training, NSCA would be the way to go.
Both ACE and AFAA offer certs for both personal trainers and group exercise instructors. Of the 2, AFAA is the most basic for new instructors, but it does not encourage "outside the box" thinking.
Anyone interested in working with winter sport athletes should defintiely consider NASM. With its empahasis on kinetic chain theory, postural alignment, motor learning and dynamic balance exercises, the training seems to be specifically designed for snow sport enthusiasts. While this is one of the harder exams to pass, snow sport instructors may have an easier time with this, since much of the text material may be similar to what someone would learn in ski instructor training.
How does all this relate to the original question? Mastery of the subject matter depends upon how well the trainer can integrate the text book material into the physical activity of the sport. This needs to happen on 2 levels.
The instructor must first sense the logic of the text material in their own body.
Then, they should be able to express and transfer this logic to their students, without having to spend too much time lecturing.
Although I've been teaching fitness since 1973, my instructional ability improved immensely when I began to write freelance fitness articles. With word count limits, I needed to make my statements as precise as possible. I soon discovered that any topic involving too much wordiness part pointed to a lack of physical integration of the material on my part. Working on these "weak points" in the physical realm enabled me to become more precise about my cues in the verbal realm.
IMHO, mastery of instructional techniques is dependent upon how fast intellectual understanding integrates with physical execution. But this may differ from person to person.