[moovova]

“...I walk 4 mph again...”

That’s fast...good for you!

[arthurus]

I learned to do that when I was a teenager and had to walk from one side of St Petersburg to the other daily. Since then I have walked from Bogalusa to Baton Rouge, backward for the first few miles til I realized that Louisiana drivers do NOT stop for hitchhikers (1965).
4mph is "forced march" in the army, or was when they did that sort of thing.