You asked me to explain the science. This is it, it's already been given to you.
"I think we can now answer this. Your pace is so slow because you are running a tiny tight course in your yard. Furthermore, your legs are getting beat up because of the constant changes in direction and tight, sharp turns. This is not how anyone is meant to train. Human physiology can support running on a tight short loop for a while - say 5000 meters for an indoor track, which is probably bigger than your yard or a marathon on an outdoor one, though probably even that would beat the hell out of one's legs. In general for distance running, you need at least a couple kilometer loop or couple mile out and back at the minimum.
Can't you tell that running in a yard is too tight to run comfortably?"
F=MA. Because you are always having to change directions (A). during your "run" the F output is greater than it should be which will lead to injury and you wont get the training adaptation you're looking for.
And yes, people tell you lies on here all the time because you're gullible and insufferable.