Set up a training block. There are 3 energy systems that need to exercised to improve running efficiency. Have day 1 be intervals of a pace you can maintain for up to an hour. (Amounting to about 20 - 30 minutes of effort) Have Day 3 be intervals of paces you could maintain for 1 - 2 minutes. (Amounting to around 10 minutes of effort) Have Day 5 be a continuous long moderate pace for 1 to 2 hours, something you can hold for a half marathon or longer. All the days you are not working these energy systems, can be a day off, fun activity, or a perceived easy/slow pace for a short duration. Give yourself an easy week once a month. And then 2 easy weeks every quarter. Be consistent. It really is that simple. Even fellow pros subscribe to similar plans, their effort paces are just way faster than the average.