These are the most reputable by a mile. Others are more or less a mail-order cert thatās not much more than a money making scheme. Iām sure thereās an exception or two, but I donāt know them personally. NSCA is THE standard when it comes to being a college and above level strength and conditioning coach. ACSM is gaining some ground, but ACSM has in the past been almost exclusively an add-on cert to PT, ATC, etc. I think ACSM had the PES (performance enhancement specialist) letters behind it for a while if my memory serves me right.
A previous boss wanted the core of us who worked in the collegeās fitness center to get personal training certification. She figured weād learn a lot and it would be useful. She did a lot of research and felt AFFA or AFA (canāt remember if there were one of two Fs) was a reputable organization and it would meet our goals. We went through a weekend course that was brutal. All we learned was how to do an initial intake with a BS few standardized tests, and anatomy. The biggest waste of my time ever, and thatās saying a lot. People asked several times how to put a program together for clients. The response every time was āitās the personal trainerās responsibility to learn that on their ownā along with an eye roll. The teachersā response to safely perform some lifts was equally non-existent.
Look up NSCA and ACSM. Alternatively if youāre strictly interested in kettlebell stuff, try talking in-person to some local trainers.