However, on subsequent repetitions during the eccentric portion of the lift elastic energy gets stored in your muscles which makes the subsequent concentric repetitions easier. This also happens in the deadlift, where the first rep has no stretch-reflex aid, while the subsequent repetitions do.
Isn’t the point of a deadlift to bring it to a “dead” stop?
That depends on the style. Some lower the weight slowly to just kiss the floor and do not unload the body but go straight into the next rep. Those who do it this way do have the stored energy Ukrainian is talking about.
The more common method that I think you are referring to, where the weight is set on the floor – for that matter it may have been lowered pretty quickly and even mostly dropped the last few inches – and the body is unloaded and the lifter so to speak re-sets himself for the next rep, this method does not have the stored energy effect for the next rep.
At least, not stored energy from the previous rep. Depending on the style, there can be a momentary storage of energy from the body exploding upwards and some stretch occurring before the bar and then the plates move, but that is different and unrelated to the overhead press.
I agree, stored energy is the principal explanation for Moon Knight’s finding. Another reason, but I think not as important, is neural warmup. As that weight is first felt, the nervous system may judge it “too heavy” and not fire sufficiently, without the leg drive, to generate that much force, but after having done the assisted rep, the weight is feeling more familiar and the nervous system is now convinced, “OK, generating this amount of force is doable, no problem.”
But, that is probably not worth as much off the start of a rep as the stretch effect is.