Competitive riders receive coaching and use spin analyzers specifically to equalize force throughout the entire 360 degrees of the spin.

By distributing the force, or the expenditure of watts, throughout the spin, one also distributes the workload to a larger number of muscles, so that no one muscle or group of muscles becomes unduly or prematurely fatigued.

This in turn lets the cardiovascular system do its full job of providing oxygen and sugar, and removing the byproducts of work.

If a muscle or muscle group fails prematurely due to carrying more than its share of the work load, cardiovascular fitness becomes moot.

Spread the work throughout the spin and to as many muscles of the body as possible.

For example, our trunk muscles, when properly organized and recruited, contribute much more to our spin than it would seem on the surface.
Some natural athletes utilize their core muscles without thinking about it; and, the rest of us have to learn how to use them.

The more of our body's parts we use, the less energy each part has to produce.