There are no weights involved here, only power you yourself generate. Basically, it is you against you. The stronger you pull on the way up, the stronger you get pulled down …and there the magic happens. Inertia of the rotating flywheel points to the opposite direction from the force you are generating when you change the direction of your movement. When you are using weights the force of gravity is a constant, here there are no weights yet the force with which you get pulled down can be greater than the force of gravity because of the acceleration you yourself generate while pulling upwards. That being said, it is entirely up to you how hard you want to make this …the idea though, at least how I see it, is to be a savage when you use this machine.
This is a unique machine — full disclosure — it was provided to me by Anže Skaza’s company free of charge. I am experimenting with it on my own and am not bound by any agreement how to present my findings and/or advice regarding its use. As far as I am concerned that is the only way anyone should test and review any equipment.
Obviously, an exxcentric kBox machine is not something the majority will ever have available. You can emulate what I am showing here with the use of bands. While not the same, it will have a similar flavour. You can try speed deadlifts at light weight, something in the range of maybe 20-30% of your max, combined with rubber bands attached on the sides of your bar, to generate additional downward pulling force on top and to also to pull you down faster. kBox allows me to start my pull quite low, meaning you would need to add quite a bit of deficit to your deadlift setup.
I did both variants just to compare and they both allow for speedy and explosive movement which is what every athlete needs in their training. Both variants allow for high speed of movement, weight version feels more natural and what we are used to feeling when lifting a certain weight, while kbox has an entirely unique dynamic defined by how strong you pull in the opposite direction of that spinning flywheel. Once you get going, there is a high eccentric force at the beginning of and the end of each pull. Instead of just trying to lift from the floor you need to additionally fight hard not to get slammed into the ground, while theoretically, you can rest on top of each banded deadlift there is absolutely no rest once you get going on kBox. It can be as brutal as you make it.
Marck Goran Lorencin
PS. One additional side-note regarding ROM (range of motion) for how I prefer to execute my deadlifts in general. As I do not train for a competition style of execution, where there are certain rules for what counts for a valid lift, I am not obliged to follow competition rules. I much prefer a slightly shortened range of motion, not fully extending my hips on top and thereby always maintaining high tension throughout my core as opposed to and loosening of core tension the majority seeks when reaching their fully extended hips. If you have your reasons for the need to fully open your hips that is fine as long as you actually know why this is good for you, or needed for that matter. I do not compete in any strength sport, I do, however aim for highest performance while at the same time managing risks involved with training at the highest levels of any kind.