I use this technique quite a lot, but somebody else wrote about it in a way better than I could. If you can do two boring tasks at the same time you’ll have an enjoyable experience.
I’ve noticed several related things: 1. I could easily study flashcards while walking. This was less mysterious because I coded walking as pleasant. 2. I can’ t bear to watch TV sitting down. Walking on a treadmill makes it bearable. This didn’t puzzle me because I coded TV watching as pleasant and sitting as unpleasant (although I sit by choice while doing many other things). 3. I have Pimsler Chinese lessons (audio). I can painlessly listen to them while walking. While stationary (sitting or standing), it’s hard to listen to them. 4. When writing (during which I sit), it’s very effective to work for 40 minutes and then walk on my treadmill watching something enjoyable for 20 minutes. I can repeat that cycle many times. 5. Allen Neuringer found he was better at memorization while moving than while stationary. 6. There’s some sort of movement/thinking connection — we move our arms when we talk, we may like to walk while we talk, maybe walking makes it easier to think, and so on.
You could say that walking causes a “thirst” for learning or learning causes a “thirst” for walking. Except that the “thirst” is so hidden I discovered it only by accident. Whereas actual thirst is obvious. The usual idea is that what’s pleasant shows what’s good for us — e.g., water is pleasant when we are thirsty. Yet if walking is good for us — a common idea — why isn’t it pleasant all by itself? And if Anki is good for us, why isn’t it pleasant all by itself? The Anki/treadmill symmetry is odd because lots of people think we need exercise to be healthy but I’ve never heard someone say we need to study to be healthy.