I found this article on tnation. Can you please explain why there are different opinions on this matter?
My conclusion? The eccentric phase does not need to be emphasized for the purpose of enhancing size and strength. Don’t get me wrong, the eccentric phase is just as important — maybe even more important — as the concentric phase, but the stimulus it receives with traditional, fast contractions takes care of all your training needs.
If you do emphasize the eccentric phase, it can lead to excessive DOMS, and that’s something that doesn’t pair well with frequent training sessions. By emphasizing the eccentric phase with slow tempos or supramaximal loads, you’re only extending your recovery period as your immune system deals with excessive muscle soreness, elevated creatine kinase activity, and limb swelling. I’m not a fan of any strategy that augments the recovery period.
My bottom line on eccentric contractions:
Train the eccentric phase with the same speed and load as the concentric phase.
Perform the eccentric phase as fast as possible while controlling the movement.
There’s no correlation between excessive, eccentric-induced soreness and hypertrophy.