...you can do a 3 week gym course and become a 'coach'. Whats a coach know after 3 weeks?
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Short Term Personal Training Certifications'
Yes, there are some short term course that will allow someone to obtain a Personal Training Certification.
However, the organization with the short term courses that certify someone as a Personal Training are not usually recognized by Reputable Health Clubs or Gym.
Obtaining a Personal Training Certification from a Reputable Organization is difficult. Some of the Personal Training Certification from organization like the National Strength and Condition Association (NSCA) and the American College of Sports Medicine (ASCM) require a College Degree just to take the test.
The NSCA and ACSM are at the top of the list the Personal Training Certification, when it come to being Reputable. Fewer individual are certified with these two organization because they are harder to obtain.
There are other more popular certification with other Personal Training Organization. That due to the fact that they are less demanding. In other word, easier to pass.
Your Novice Status'
Your novice status mean that you don't know enough to know who is providing you with good information and who isn't, as you eluded to in your post.
That means that "everyone I know that is successful at (the) gym" may or may not know what they are talking about; great athletes traditionally make poor coaches.
Take Homes Message
Categorizing all Personal Trainer as "Waste of money" is a "Snap Shot" perspective. It doesn't provide you with "Whole Picture".
Steve and The Nail
As they have stated, there are some good coaches that can help you, providing you take the time to find them.
Kenny Croxdale