What exactly does this tells me?
This is the amount of physiological work performed in lifting the weight from its lowest point in any particular repetition to its highest point. Its calculated by the following equation; W=mgh. Where W =work (Joules), m = mass, g= gravity (9.81) and h = height of lift.
Whilst Conc Work is not a core metric it can provide additional information about the exercise being performed.
Quite simply if you do the exact same exercise movement and same weight with the same number of reps, then if the total work from set 2 is greater than set 1 then the bar has moved through a greater range of motion.
Or if for example an athlete tends to shorten their depth when squatting as they fatigue.. if they are doing the same weight/rep scheme you might see them keep the same velocity, but if they shorten the depth, then this will be reflected in a smaller value for Conc Work.
Similarly.. two athletes do the exact same Weight and Rep scheme, one is taller than the other.. they could lift at the exact same velocities, but the taller guy might do more mechanical work because he moves the weight over a greater distance.