I saw Jeff Cavaliere from YouTube channel Athleanx mention those in a couple of videos.
It’s basically loading up the stack on an exercise like cable fly with too much weight to actually be able to move it and then try and do a rep as hard as possible for n seconds. It can be applied to exercises like cable curls too.
The supposed benefit is increased motor unit recruitment for actual sets and, more interestingly (to me at least), increased muscle tone at rest.
I’ve also seen a variation of these used in the layer system, with the purpose of “turning on” the nervous system and use that potentiation for subsequent sets.
Anyone ever used them? Are there actually any actual aesthetic benefits like increased muscle tone and “harder” look?