There are many research articles on eccentric training and when done infrequently at a high intensity the benefits of it.
I had been doing Eccentric training or "Negatives" since I was a teenager working in the Old Torture Chamber known as a "Nautilus Gym".
Casey Viator and Ellington Darden were the two fellas that I kept up with and they were advocates of this type of training back in the '70's.
When going ALL out, there was no way to go LONG in duration. Either workout bout total time OR even the rep, as most muscle will reach an inability to fire in 60-70 seconds when going all out.
At this level of mind/body connections you couldn't do it frequently either.
Last Friday and today were about it for this block of training.
This stuff absolutely FRIES a person.
When doing the proper negative rep, you can't just hold the rep. You MUST fight the entire range of motion during the lengthening or deceleration period.
You can HOLD (Static) more weight than you can pick up (Concentric). You can let down (Eccentric) more weight than you can HOLD.
This means you can use 100% + some weight of a one rep max during the exercise.
CAUTION!!! Seriously for the advanced lifter ONLY!
D.O.M.S. is imminent. THIS is going to HURT!
But I like it for the mental toughness part as well.
Pull ups: 2x3xBody weight + 25 lb vest
Dips: 2x3x Body Weight + 25
Chin Ups: 2x3x Body Weight +25
American Bar Skull Crush: 2x3x95
Preacher Curl: 2x3x95