I work as a freelance personal trainer and work with different gyms and individuals. Newly opened gyms often hire me to help them interview new trainers, lead classes, or setup fitness schedules. Once a gym gets going and is fully staffed, I will usually leave to help start up another gym, or just go back to training individuals. I let the gyms know in advance that I'm not there to be a full-time trainer. As a mom I like having the flexibility to spend a few weeks or months at home with my kids. The clients also seem to appreciate my flexibility.

As far as I know I have a very good reputation in my business. My clients seem to love me as do the people I work with at the gyms. they stay in touch well after I leave. recently 2 new gyms in the area were looking for someone with my background available on a temporary basis, a perfect match for me. But both places rejected me without an interview only saying that I wasn't a good match for the jobs. I asked for more reasons but they wouldn't elaborate. I know almost for a fact that I am probably the best match within 200 miles, and they have had their job ad open for 3 weeks since rejecting me. I'm not sure who works at the new gyms, but I think it might be some competitive former colleagues who didn't like my energetic style and frankly seemed jealous of my experience. I never conflicted with them but could always tell that they didn't like me. But they had no real reason to criticize my work. I always left jobs on good terms.

How can I find out if these people might be blackballing me? Is it illegal to reject a job applicant for no real reason. I can't think of any good reason why they wouldn't at least interview me. I'm worried someone might be saying something bad and untrue about me but don't know how to find out.

Have some friends call the Gyms you've worked at pretending to be potential employers, and have them ask the standard questions:

Did this person work for you from X to Y.
Would you hire this person again.

if your friends get anything other than a 'yes', 'yes'. then you have grounds for a lawsuit. in the very least you can get them to stop.