You will not solve this, as it depends on how fill our liver is at the time, and how much glycogen we have stored in our legs. You may even find that yesterdays walk has more effect on today’s BG then today’s walk….
A fast walk (or run) may even result in our BG going up, as glycogen is transferred from our liver to power our legs, but then the liver will become a lot more insulin sensitive until its glycogen stores are rebuilt, resulting in a lower BG peak from the next meal of carbs or protain.
Walking has been proved in a lot of reserach to lower BG over the long term, I know it works for me. Also if I go for a walk in the rain after dinner, by wife does the washing up.....