The ground teaches.

Flat ground asks one question, over and over. Uneven ground asks a different question with every step: a camber here, a loose stone there, a step height the eye measured slightly wrong. The foot answers before you have time to think about it.

That answering is the education. Feet kept on perfectly flat, perfectly cushioned surfaces stop being asked anything, and an unasked question is eventually an unanswerable one.

You do not need a mountain. A curb, a cobbled lane, a stretch of grass, the worn stone steps of an old building: any of them will quiz the foot a hundred times in a minute.

Seek out one honest surface a day and let it interrogate you a little. The body likes being asked.