Also, a coach helps you keep motivated. This is very, very important. I know many here think they can just motivate themselves but that's not true. Your body always finds a way to fool you into thinking you are giving it your all.
I think this is the most important factor. If the athlete (beauty contestant) believes and respects the trainer/guru it can really help, even if the trainer screws up some things. And there's always going to debate on everything, from how to perform exercises to what drugs to take in what quantities.
It's easy to take shortcuts, for example, cut out better exercises for "easier" ones. I've done it, everyone has. Conversely, a few may need to be told when to pull back occasionally when fatigue is mounting too much. Schedule in periods of lesser intensity. Schedule in true HRT periods or even complete off periods.
Everything starts in the mind. If the coach believes in you and you respect him then it will help psychologically.
Then there are the personalities who are uncoachable. I'm one of them. I love getting input but I like to make the final calls.
Due to instagram many pros are getting advice from exercise physiologist/biomechanics nerds nowadays.
Like from this fella:
https://instagram.com/coach_kassem?utm_medium=copy_linkEven absolute freaks like Jordan Peters has sought coaching from him. The number of bodybuilders doing "his" exercises on IG is ridiculous. Everyone is doing his lat pulldowns - for example he says the back should be straight instead of arched for lat activation, little things like that.
I do not believe Jay had a trainer type coach like a Charles glass during his career, a drug and nutrition coach, yes, but not somebody counting reps and telling him what exercises to do
Everyone speaks highly of Charles Glass but I find manyy of his exercise selections a bit ridiculous. For example this one:
https://www.instagram.com/reel/CUaSqXLl53t/?utm_medium=copy_linkIs there any good reason to do that exercise when there are many more stable exercises where you can actually load the glutes with meaningful loads?