A perceived limitation of flywheel resistance training (FRT) was the guess work around quantifying load on these devices. The uncertainty I think comes from a number of origins:
1) Older technologies weren’t instrumented so you had no idea of the load the flywheel devices were producing.
2) Some flywheel technologies are very different e.g., conical vs cylinder
3) Most of us were brought up understanding linear type free weight resistance training (FWRT) and variables such as 1RM, force, velocity and power. However, resistance training involving angular motion and variables such as torque, moment of inertia, etc. are somewhat foreign to many, and difficult to understand.
4) Related to the above, most of us understand what light to heavy resistance looks like with FWs, but not so with FRT.
5) We feel that there is a lot of variability associated with each repetition of FRT as the muscular work is determined by the angular work of the concentric contraction, not like the constant resistance of a FW load.
Rotary encoders attached to flywheel devices enable the measurement of angular displacement over time, from which many other variables can be derived some of which you can see in the picture. This rotary technology coupled with easy to use software, have made things a lot easier to quantify load.
What’s the next step? Users getting to understand angular resistance training and the important metrics. However, to make it easier for the user, some companies such as Exerfly have converted the angular measurements to linear equivalents for easier digestion.