180 rpm means round per minute, revolution per minute or spm actually what is steps per minute. 90 steps on each side accounting to 180 total steps. In reality, running technique, surface, the size of the runner, leg length, will all determine your natural cadence. Why 180 ? It is close to the natural rhythm and resonance of the body and can be harmonised with heart rate and breathing. Therefore it is a cadence what handles impact on a way that running itself will less likely disturb vital body functions like heart rate, digestion, circulation, breathing, kidney function and so on. When you run with a 180 cadence, your muscle contractions, impact absorption and energy return are harmonically paired up to provide you an efficacious movement with the most reduced risk.
In reality all of us are different and our habits are different. I would rather say that a 170 to 185 range is closer to the reality and better than setting up an ultimatum. However, this doesn’t mean that if we ran at 172 or even wat 182, that we are okay ! It means that our workouts focusing on technique are reaping it’s fruits and we should continue doing form, posture and cadence practices !
The easiest way to imprint high cadence into our mind, is to slow down the heart rate and do cadence intervals with run schooling drills. What you want is for instance to set up a double screen on your watch, AVERAGE LAP CADENCE and LAP TIME. You can now do for instance 200m of high cadence low heart rate running, then press the LAP button, do 3-4 minute of drills, then again press the LAP button and run for 200m and so on. You can include quality run specific strength and conditioning to these kind of practices. These sort of workouts will imprint good habits, as if with a tired body and locally exhausted muscles and compromised strength you can run with proper form and quality cadence, you can assure to keep high cadence and good form when fresh as a daisy !
(On your watch you can see immediate feedback, but post workout too, you can have a quick look at the AVGCadence of each run lap to see how you improve and to understand what need to be worked on !)