By programming your trainer to “force” you to do certain resistances, you are leaving out the most valuable components of your workouts that actually make you better.
Basically, by doing your intervals in ERG mode, you are taking an important part of cycling out, adapting the pedal stroke to changes. This is like repeatedly training for baseball hitting from a T instead of from a pitch. Sure the force is there, but all the key neuromuscular training is missing. And this is the training that takes years to develop.
Being able to “hit” your target power should not be something you should be forced to do. Learning how to create and hold the power is a huge part of the sport of cycling.
We refer to the concept of proper “hitting the power” technique as Power Control. This is basically how efficient you are working a specific physiological zone.
Power Control is made up of two components: a Power Floor and an Power Ceiling.
The Power Floor is the power number listed in your workout. With the PF your objective is to try and hold your effort right above this target number, avoiding dropping it, or “breaking” through the floor. This should be your primary focus with Power Control. As you become more in control during the interval with the number, you next increase your focus to include your Power Ceiling. The PC is how far you are deviating above the PF with occasional power spikes. The stronger and more efficient you become, the closer the PC lowers to the PF, without breaking through it.
As you become more advanced with your power zones, we recommend increasing the complexity in the structure of your efforts, cadences, body positions, and transitions to require more advanced the Power Control. We recommend doing your intervals on the changing terrain offered on ZWIFT to make working the Power Control in relation to how you would outdoors.
Overall, going fast in cycling is about not just the force the athlete can produce, but the technique of the athlete while producing the effort. To become a better and faster cyclist, the two must go together in sync.