This is a very good paper that will help you out (Intervals, Thresholds, and Long Slow Distance: the Role of Intensity and Duration in Endurance Training), htt

This is a very good paper that will help you out (Intervals, Thresholds, and Long Slow Distance: the Role of Intensity and Duration in Endurance Training), http://www.sportsci.org/2009/ss.htm#_Toc245522384 http://www.sportsci.org/2009/ss.htm#_Toc245522384 Here is a good video he gave on polarized training, http://www.canal-insep.fr/fr/training-periodization-deep-root-cultural-heritage-and-innovative-paradigms-2013/ei_13_10_va_pr_stephen_seiler-mov http://www.canal-insep.fr/fr/training-periodization-deep-roo... There is also the Phil Maffetone 180-Formula, http://philmaffetone.com/180-formula/ http://philmaffetone.com/180-formula/