I just told you its a mistake to move feet a lot, runners don't do that. Also you'll expel a lot of energy yo won't last more than 15 mins game by moving that fast based on common biology. I am no doctor and I can tell you that every player in NHL has similar stamina work ethic etc.. Sedins could do the grouse grind in 35 mins because their legs were well built etc but they were super slow...
Its something else McDavid is doing, possibly additives no way anything else can be explained