Do I need a personal trainer to keep me from being injured in the gym?
So, a personal trainer is kind of like a tour guide that you hire for your journey into uncharted territory, like a trip down the Amazon.
The first thing that you don’t want your tour guide to do is paddle out to those dangerous rapids or over a nearby waterfall. You would prefer him/her to avoid taking you too close to unsociable crocodiles with bad breath or dumping you unawares into a local pool of hungry piranhas around lunchtime.
Yes, the number one duty of a responsible PT is “Do No Harm”, much like the Hippocratic Oath-oriented Doctor or Dentist.
This professional & responsible PT, along with demystifying the esotric, humbug-infested process of getting fit, enabling you to make rapid progress towards your fitness goal is tasked to do so in a sandboxed, safe environment, always keeping injury risk to a bare minimum. The keywords here being professional and responsible, as competency level in my profession tends to pretty much mimic any other profession, perhaps a little less so.
The gist of it is that, should you eventually decide that obtaining a trainer might be worth the cost, you need to be a canny shopper.
The question you ask is simply answered: you might be able to do it yourself, if you are a fast learner and can keep your wits about you, but always proceed with caution. You must learn proper form and be realistic about your strengths and weaknesses, along with being able to seek out and discover movements that work for you. In essence, the dirty work still needs to be done, you’re just going to be the one who tasks himself to do it.