Principle of Reversibility

Some time ago, I completed a course called “Science of Exercise”.

One of the very first thing they teach, is the “principle of reversibility”, that explains that after a period of not using the muscles you’ve trained, those muscles go back to baseline level.

I claim that this principle is also applicable to learning in general, and more specific, to mathematics.

If you don’t use the mathematics muscles you’ve developed for some time, you eventually lose your progress and you go back to some baseline level.

I note this because I recognize that after I passed some hard subjects on university, I usually didn’t re-use the lessons I learned, and thus eventually lost my progress.

After going through the hard work of learning the things in the first place, the “maintainance” of the knowledge is much less costly, and in many situations, it’s worth the effort.

My conclussion is that learning a hard topic and then not using it for a long period of time to the point you recall almost nothing of it, is as useful as going to the gym, get to be able to lift 100kg on some exercise, then not practicing it for a long time.

The next time you try to do it, even 20kg will be challenging. The next time you try to recall the hard concepts, even the trivial definitions will be unfamiliar.

But, if you keep hitting the exercise every once in a while, then you will be able to maintain those 100kg in the long run. If you keep practicing or at least using the results you’ve gotten in that hard subject, you will be able to maintain the knowledge you’ve gained.