How do you accomplish that?
Make use of the Maffetone's Method and stick with it,
Here are some links to investigate for yourself:
http://philmaffetone.com/180-formula
http://www.philmaffetone.com/alleninterview
http://www.ignition-fitness.com/about/articles/speed-up-by-slowing-down/
http://www.enduranceplanet.com/mark-allen-and-dr-phil-maffetone-their-first-ever-dual-interview-on-the-grips-legendary-ironman-success-using-maf-method-the-current-state-of-triathlon-racing-coaching-modern-athletes/
http://www.joefrielsblog.com/2010/04/mark-allens-training.html
Merry Christmas and All the Best to you in 2015.