The muscles at the front of your thighs known as your quadriceps are some of the biggest and strongest in your body.
They play a significant role in generating power during cycling, particularly during the downstroke of the pedal.
The muscles on the underside (or rear, depending on your perspective!) of your thighs are the hamstrings, so to speak.
Since muscles can only contract, as you are probably aware, they must function in pairs to move our bones. As a result, with every pedal stroke, the hamstrings flex and relax equally as much as the quadriceps.
One of the top muscular groups is the glutes. You likely already know that the gluteus maximus is the biggest muscle in the body,
but you may not realize that it is a member of a larger muscle group that also includes the gluteus medius and gluteus minimus, like the quads and hamstrings.
The calf muscles are the next set of muscles that cycling strongly engages.
These are made up of the soleus, which is visible at the outside of the lower leg but lies beneath the gastrocnemius, which is the massive, toned muscle on the inside and outside of the lower leg.
with addition to the calf, cycling is frequently used to tone the Tibialis Anterior, which runs down the front of the shin and aids with ankle plantarflexion during the upward part of the pedal stroke.
By the way, "plantarflexion" refers to the act of pointing your toes downward during the upward portion of the pedal stroke, which is the exact opposite of "dorsiflexion."