Thanks to My Online Friend Pascal, the Doctor, Who Confirmingly Says This:

Walking is also very good. And swimming, too.
It's interesting, how little exercise one truly needs to stay in decently healthy shape. The rest is all bonus, naturally.

Yes, walking without all those devices, gadgets and those other instruments, just plain wallllllllking in the woods, or along the beach, or in the dunes - is just wonderful, and easy. And frees a choked mind.