Re last sentence - I didn't know that.
I much prefer walking to cycling tbh - especially mountain hiking & scrambling. 6 -10 hours hard graft in The Fells gives a great workout; especially for the older chap.
Aye; think it's a pretty well-known issue since you're working your muscles but not actually supporting any weight. I like walking for the sake of getting out and while I do find it mentally beneficial it's not to the same extent as a good ride IMO