The National Strength and Conditioning Association (NSCA) is a US-based professional body founded in 1978 that publishes the Journal of Strength and Conditioning Research and certifies strength professionals.
The NSCA's public certification listings describe two main credentials: the Certified Strength and Conditioning Specialist (CSCS), which requires a bachelor's degree (with specific exercise-science coursework requirements for newer candidates) and is aimed at coaches training athletes for sport performance; and the NSCA-CPT for training the general public. Both exams are NCCA-accredited and appear in the USREPS registry, and both require continuing-education credits to maintain. A trainer's claim to hold either can be checked against the NSCA's public registry.