The concentric contraction in flywheel resistance training (FRT) has received little interest compared to the eccentric contraction, however, personally I think it is the star in many ways.
First, it obviously is a necessary determinant of what happens in the eccentric contraction.
More importantly it may just offer more in the concentric phase than does traditional constant resistance training (CRT).
Let me explain.
I have posted on this a couple of times but in CRT you spend a lot of time decelerating the bar in a maximal contraction, the picture on the slide showing the force-time profile of an 81% 1RM CRT load. However, when you jump or project a load (ballistic movement), pretty much the entire concentric phase is accelerative/propulsive.
FRT on the other hand has been shown to have similar kinematics to ballistic exercises, in that if an individual performs the concentric phase maximally over the entire range of motion, most of the concentric phase can be considered accelerative/propulsive (see stylised FR signal).
This acceleration profile obviously has certain mechanical advantages and better simulates sporting performance.
Give it a go and you will understand what I mean.