Hi, currently training for my 3rd and 4th marathons. Looking for a sub 3.15 (7m27sec p/m). I can't get my head around LSRs. Would it not make more sense to practice running the required distance at your goal speed. ...I know it doesnt but would like to know why. Im worried that if I don't do 20+ at goal speed I won't be able to do it on the day. Currently out 6 days, 45+ miles a week.