There has been much debate lately on which personal training certification is better to have: A.C.E. (American Council on Exercise) or NASM (National Academy of Sports Medicine).
Both of these certifications are excellent, but I find neither of them to be all comprehensive.
In my opinion, A.C.E.'s biggest weakness is in the organization's conservative program design. Most of their program design comes from the American College of Sports Medicine, which is a very safe path — and is exactly what a novice trainer needs.
NASM follows the stability, strength and power stages of fitness, progressing a client from one ability level to the next. This gives the trainer a bit more leeway in the program design process.
NASM is famous for using a squat test assessment to find muscular imbalances in clients. This is a great tool, and I use this test on a very regular basis. That being said, there is a major weakness in the way trainers present this test. Depending on the clients body positions or flaws, NASM philosophy is that the imbalance could be in one of two places in the body, making it necessary to perform more evaluations on the client to pinpoint the imbalance. (This process needs to be more refined in order for it to be used more effectively.)
ACE's tests of separate body parts may take some extra time, but there is no guesswork — or need for additional tests — to identify the imbalance. (I know I used really broad terms here, but that is so I don't bore anyone to tears —or worse, suicide.)
All of this information is for the trainer. Now, what does this mean for you, the client?
Absolutely nothing. Are you going to care how your trainer comes to the conclusion on which of your muscle are tight, or which ones need more strengthening? Probably not. What's important is not what process you use, but the results you obtain.
On two separate occasions recently, I was able to see firsthand two new trainers with the same certifications (though not all four having the same certification) apply their knowledge.
I saw huge differences in the trainers' abilities — which brings up an even more important rule for the client: talent, not certification, makes the trainer. Don't choose a trainer solely on education and certification alone. Watch how the trainers at your gym work out with their clients, and ask gym employees whose opinions you value which trainers they would choose. Give your trainer a chance, but if you aren't getting the results, don't be afraid to try someone new.
Bottom line is this: certification is meaningless if your trainer is not getting you results. The true test of a trainer is how that knowledge is applied.