You can visit a Strength Training Specialist if you have any concern with Pain ( Typically Back / Neck/ Knee etc ) or Mobility ( Reduced Flexibility / Low Range of Motion etc ) . Also SInce Resistance Training Specialist is medicine free treatment with no side efects , Strength Training Specialist should be your First option for seeking treatment / consultation. You dont need a Doctor's prescription for the same. After proper assesment ,if a Strength Training Specialist feels that your condition needs interention by a doctor ( ortho/ neuro / other ), he / she would refer you to the right specialisit.