Look all the good pro or not pro bodybuilder, they started with out trainers, all the Mr.Os. I never used a trainer, I see many workout posted on you tube even here on PM it don`t impresses me, most try to lift to heavy to impress others, you need to go beyond failure on each set with correct form. The best worked for me and still working at age almost 72 the variable resistant training, I started back in the late 60s. You need to train your legs brutal, it will help your upper body growth indirectly.