Why are Cycling Power Models Important?

Once you understand how cycles move, your next cycling question becomes given my current training level, what is realistic in terms of which cycling models I can take on. Your current training level is defined in terms of your power generation abilities for various lengths of time.

We have discussed how to measure your levels in our sections on Cyclist Modeling, so we start here with the assumption you know your current levels. Power Models take a given scenario, assume you want to ride it at a given average speed, and then computes the scenario power reqt. This can then be compared against your current level to see if it is “within your wheelhouse.”

Computing Scenario Power Requirements

Power computations are one of the simpler exercises in Physical Cycling because of the non intuitive but simple relation expressed as

Power = Force ⋅ Velocity

So if you simply take the Force equation and multiply each of terms by your desired velocity, you get your power requirements. In fact, as you multiply each of the terms, what you get is the power required to respond to that particular force.

Overcoming Resistance

Suppose you are riding on the flat. What must you power output be to just balance out the resistance forces and maintain your speed v?

F = RollingResistance + AerodynamicDrag

P = (RollingResistance + AerodynamicDrag) ⋅ Velocity

Using our rearranged force equation, this becomes

P = Crr ⋅  Weight ⋅  Velocity + AeroK ⋅  Velocity ³

Notice that the power needed to overcome drag is v³ which explains why drag is dominant at high speeds.

Next Topic:   Cycling Motion Equations