This was a recent topic of discussion on the GAIN forum:
I'm not sure why this is rearing it's head again. The concept of eccentric resistance training was popular in the 80s. If I'm not mistaken, at the end of the decade there were even companies that were iimplementing it in isokinetic machines.
In my mind, strength training is more than just sarcomeres. There's a motor control element to it. On page 28 of Richard Magill's new edition of his "Motor learning and Control" book, he says, "..researchers interested.in understanding the action preparation process are able to to obtain more specific insights into what occurs as a person prepares to move. Most reseachers agree that the premotor time is a measure of of the receipt and transmission of information from the environment, through the nervous system, to the muscle itself. The time interval seems to be an indicator of perceptual and cognitive decision making activity in which the person engages while preparing an action."
The machine scenario seems not to be concerned with any of this, only overloading the eccentric phase of a specific unidirectional, uni plane movement.
Eccentric overload requires a good amount of isometric stabilization to handle the extra load. Let's take a squat. If we use a weight beyond our 3R maximum we need to lower the weight very slowly and use spotters for the concentric portion to avoid injury. However, in my scenario, we can use a weight well below our 3R max, but instead actually "pull" the weight down to increase the eccentric momentum; then abruptly stop it at the bottom and concentrically return it under our own power. The neural component of the squat can be ehanced even further with a command by the coach to abruptly freeze and hold any position for a given amount of time. It also creates a great anaerobic effect.