Personal Trainer refers to an educated person who has sufficient knowledge of Anatomy, Physiology, Biomechanics, Energy systems and even Nutrition to be given and applied to specific Gender or client depending upon the Assessment he/she does whereas Building a Body using progressive resistance exercises for Demonstartion and Glamour purposes is different.
Just like if someone learns how to drive a car, is not to be considered a driver untill he/she gets a license by undergoing a practical test to prove to the authorities that one is well versed with the nuances of driving a vehicle. He/she has to understand certain mechanisms and functioning of a car, rules and regulations to follow on the road to avoid accidents and injuries.
In the same way Personal trainer is the one who study various mechanisms behind the working of specific muscles and bones of different body types along with the knowledge of nutrition which has to be provided to the client for a specific goal to be achieved. A Personal Trainer faces challenges in training people from various backgrounds such as doctors, lawyers, engineers and specially those who are dealing with high blood pressure, diabetes and back pain. If a trainer is not educated in his/her field, the condition of the client might worsen as each and every exercise has a specific technique, reason and variation which has to be prescribed to the client depending upon the assessment done.
Remember, A lawyer ruins his clients’ fate without thorough knowledge of law and legality!