Musclechemistry Board Certified Member
Many trainers advocate for using slow and controlled lifting tempos as they believe this will lead to greater growth. However, this review found that lifting tempo has no effect on muscle growth. Furthermore, extremely slow tempos were actually less effective for growth than fast tempos. Let the weight, fatigue level, and lifting form dictate your lifting tempo while training.
Source: Schoenfeld, B. J., Ogborn, D. I., & Krieger, J. W. (2015). Effect of repetition duration during resistance training on muscle hypertrophy: a systematic review and meta-analysis. Sports Medicine, 45(4), 577-585.