Training to failure is not necessary for hypertrophy and may be detrimental to strength gains.

“So, failure, an operational definition would be the inability to perform another repetition with proper form. And we carried out a meta-analysis recently on this topic and the bottom line is that, and that's kind of the "go hard or go home philosophy," that's the bodybuilding mentality, "go hard or go home," every set needs to be taken to failure. The evidence does not indicate that's the case. So, certainly, you need to train with a high amount of effort but certainly to take every set to failure...not only is it not...doesn't show any benefit for hypertrophy, it actually showed a small detriment for strength.”