Cadence in cycling is defined as the number of revolutions per minute (RPM) you complete at a given speed.
The power you are able to produce on the bike is the product of torque (force on the pedal) x angular velocity (or your pedal speed). Based on this formula it is easy to see why an increase or decrease in your cycling cadence will directly impact the power you produce on the bike. While many cyclists will work towards their sought-after goal of increasing their threshold power, potentially a new benchmark could be to increase their cycling efficiency by focusing on cadence work.
Running and swimming are sports where poor form and efficiency will show themselves quickly by producing slower results. Cycling on the other hand is more forgiving and can allow people to ride relatively well even with poor pedaling form. When you watch elite cyclists, their ability to produce smooth cyclical motions seems effortless and much of this is attributed to their neuromuscular coordination that has been developed over years in the saddle, as well as attention to detail in improving cadence.
We can relate this to a cycling pedal stroke. When pedaling a complete revolution, your muscles are not working independently. Leg muscles including the quads (vastus lateralis and medialis, rectus femoris), and hamstrings (biceps femoris (long and short head), semitendinosus, and semimembranosus) are all working together to produce smooth movement. If they worked independently, your motion would be very stiff and jerky. As the quadriceps lengthen and produce force into the pedals, your hamstrings shorten and produce a pulling movement against this force.
For the smooth, fluid movement to be produced requires complete synchronization of many different systems to communicate harmoniously with one another. You can think of it as an orchestra where many different instruments play simultaneously to produce a cohesive piece of music. This does not happen by luck, but by neuromuscular coordination. At first, the sound is a bit clumsy and incohesive, but over time and through practice it becomes one succinct sound. When your body performs high cadence work, your body communicates contraction and relaxation of the muscles involved out of sync and rhythm. This increase in neuromuscular communication is due to co-contraction. Co-contraction involves the two sets of muscles that surround a joint, flexors and extensors, and their simultaneous activation (trying to shorten.) An example of co-contraction would be flexing your bicep (elbow flexor) and tricep (elbow extensor) at the same time. Both muscles are contracting, but the lower arm is not moving.