[Cycling] Which muscles do the work?

http://better-rider.com/training/bikefit.html

The major muscle groups:



Glutes : Largest muscle group in the body, drives the leg down from the hip.
Pushes down at the front of the pedal stroke



Quads : Extends the leg at the knee.
Kicks forward at the top of the pedal stroke



Hamstrings : Opposing muscle group to the quads, flexes the leg at the knee.
Pulls back at the bottom of the pedal stroke



Hip flexors : Opposing muscle group to the glutes, lifts the leg up at the hip.
Pulls up at the back of the pedal stroke