When you’re on your indoor bike you are still experiencing the same forces that you would when cycling outdoors, they’re just created by different means. Things like inertia and resistance are still very real.
Resistance and inertia
When you pedal on an indoor trainer you are essentially creating forward momentum, or inertia. The momentum created in the trainer has the same effect as you would experience out on the open road. Similarly to being out on the road, the inertia created here stops your trainer from decelerating your bike too quickly. That wouldn’t feel right, and would quickly pull you out of your thoughts of cycling through the French countryside back to your basement.
Bike trainers offer a number of different resistance unit, from wind through to motor which replicate everything from cycling on a flat road all the way through to a stiff headwind or the Alpe d’Huez.
The importance of the flywheel
The flywheel on your trainer is the secret to giving you a realistic ride. The manufacturers are constantly competing to find ways to make flywheels lighter and smaller while still able to give you a smooth ride.
If you remember the good old days flywheels used to weigh as much as a house (give or take).
The flywheel works together with the resistance unit on your trainer to deliver just the right amount of inertia. They need to be finally balanced and manufactured to be as smooth as possible.
You can split the science of indoor trainers into two parts, the physics and the maths. While inertia, resistance and flywheels are very much in the physics camp, the way your trainer reacts to your efforts depends very much on the mathematics behind it.
This is manifested in the resistance curve which is unique to every trainer.
There are a number of different types of resistance curves that you will encounter while training, they are all useful in certain aspects of your training.
Linear resistance curves
A linear resistance curve isn’t actually a curve at all, it’s a straight line. The resistance increases in measured steps depending on the speed you cycle at or the gear you are in. It’s not a very realistic ride feeling.
Progressive resistance curves
This is a very realistic training feeling. The resistance increases by ever higher amounts the faster you go. You know the feeling from being outside, the difficulty increases by twice as much when you ride twice as fast. It’s not perfect but it’s not far off.
Motor controlled resistance curves
These are adaptive curves which are controlled by a computer unit and attempts to replicate the feeling of cycling on the road as closely as possible.
What’s your favorite type of resistance curve? I’d love to hear from you in the comments.