…and then I should add, even if you already have a certification, it still takes a good amount of time to study for a second PT certification. The way they program design can be totally different. Although the physiology doesn’t change, sometimes the acronyms change; for example, one certification used “frequency, intensity, time, type” and another one used “frequency, intensity, duration, mode” for variables that one could change in an exercise program.
It is dependent on the person’s background and knowledge. Years ago I took a number cert exams just to experience them for my programs that teach Personal Training to hopeful instructors. I passed them without extra studying, but I already had the background.
I wouldn’t want an instructor to just manage to take the exam though. There is so much more to being a fitness instructor.