At one time when I was younger I played lots of tennis including tournaments. While visiting a chiropractor for a lower back issue, I brought up chronic soreness in my racket arm. He was either a body builder or power lifter and may have had some familiarity with muscle soreness. He prescribed a series of exercises, using a very light weight that had the effect of stretching the arm muscles. I had suffered with the condition for many months but to my complete surprise I felt relief in just a few days and in a few weeks it was gone. My suggestion is you find someone with a sports medicine background. If they happen to also be an athlete, even better.