The advantages of seeing a specialist vs a primary care physician is that the specialist knows exactly about that field of medicine. One circumstance for a specialist: Your eye is bleeding and red, you might want to go see an ophthalmologist because they focus on the eyes. One circumstance for a primary care physician: You feel weak, dizzy and you are vomiting, you have no specific area of pain, so you might want to see a primary care physician because they know about different fields of medicine instead of just focusing on one.
It could be to avoid injuries. One reason why there are several rules in
exercising is to ensure that a person will not get injured during a
workout. Injuries can occur when one is
either handling too much weight, doing the exercise wrong, not using proper
equipment or does not have a partner or trainer assisting him.
What is the question you are asking