It has to be timed otherwise it wouldn't accomplish anything in terms of amplifying its affect. If the blowback follows the arc of the strike then it would cause all kinds of wrist strain, when its head bounces back in accordance with the extra force provided by the mechanism. Note how it would contribute to the rate of change of acceleration, i.e deceleration (more on this in a moment). It also mentions a shock damper, whatever that may be, but unless there's some kind of rotational step I don't see how it would avoid this issue. That being said does it actually make physical sense? Would this actually improve the effectiveness of a sledgehammer? The point of any kinetic weapon is to concentrate output from a more diffuse input. To spread out the force applied to you, and apply it to a much smaller area of your enemy. A human body can only engage so many muscles at one time, and each has their own limitations, in part due to the other aspects of anatomy (ligaments, tendons, whatever). I reckon f every involved part of the user can withstand more force than they are generating--or otherwise experiencing as a result of the attack (the motion and its impact), then a super sledge would make a difference. So the question is how much of a difference if any? I have no idea how to actually calculate this kind of thing. Can anyone more learned chime in?