Completely off-topic, but that goes against most of the 'expert' advice on how you should train. Running a PB really takes it out of you and recovery takes a while. You can increase foot speed with intervals and endurance by running further, but off race pace. Takes all sorts though!
I guess if you were training for a marathon you wouldn't run a normal marathon in training? My midweek training is now longer distance, slower pace and hills for endurance and stamina. Been doing that for 4-5 weeks and then achieved 3 Parkrun PB's in that time. I know this thread is about Turnbull not running but the Turnbull stuff seemed to 'run' out........