Some things, you never forget

In the last 2 weeks, everyone in the Netherlands was focussed on ice skating.
For me, unfortunetely, I was not able to try it untill yesterday (due to sick husband and children).

So in the afternoon, I went with my daughter (and slee) on the ice. I was a bit worried since (apart from 10 minutes skating a year ago) it was about 10 years ago since I stood on my ice skates. To my big surprise, I put them on and skated on the ice without a problem!!

So ice skating is really like riding a bike: once you have learned it, you never forget how to do it!

That made me wonder why you do not forget how to ride a bike or ice skate (compared to the maths I learned at university and cannot reproduce now). Is it pure the physical excersise or the age that I learned how to do that? Or is it perhaps the intensity of it (I used to ride a bike every day and ice skate every year). A lot of 'knowledge' learned at school (like physics) however is learned within a certain (short) timeframe and (in my case) not used that much afterwards (except again within a short timeframe).

Any ideas about this?