Most people are incorrectly or inefficiently preparing for endurance events lasting over an hour by focusing on their anaerobic threshold (AT) instead of their aerobic threshold (AeT).
If you analyze the endurance training programs of elite athletes, you will find that the majority of their mileage is done at a relatively slow pace within their aerobic threshold. According to a review of Training Characteristics of World-Class Distance Runners, elite runners train 11-14 times per week and follow a polarized training regime that follows an 80-20 intensity split, where 80% of their total running distance is performed at low intensity within zone 1-2 and 20%, consisting of mid to high intensity training, within zone 3-5 (1). This type of training will build an athlete’s aerobic capacity and running economy while allowing the athlete to be well-rested for higher intensity workouts (2).
Eliud Kipchoge is arguably the greatest marathon runner. He earned back to back Olympic gold in 2016 and 2020 for Kenya. He is the marathon world record holder with a Berlin marathon time of 2:01:09. He also ran an unofficial sub two hour marathon with the time of 1 hour 59 minutes 40.2 seconds with an average pace of 4:33.5 minutes per mile for Ineos 1:59 Challenge (3).
In several articles, experts identify Kipchoge’s training as classic pyramidal intensity distribution. In a simplistic breakdown of his marathon training, Kipchoge divides his astounding 130 - 150 weekly miles into alternating between easy, medium, and hard days with a long run every two weeks (4). At training camp, he spends 82-84% at a very low intensity, about 8:00 per mile pace, which is an “easy run” in comparison to his marathon pace of 4:35 per mile. He does about 9-10% at moderate intensity and 7-8% at very high intensity (5). This plan allows him to train enough volume to build cardiovascular system while allowing him enough time to recover so that he can have peak performance on his high intensity track sessions on Tuesday and his long run on Thursday (6). This will also allow him to be well rested for race day.
Here is an example of what Running Coach Patrick Sang would program for Kipchoge before the London Marathon (7):
Monday AM: 10-13 Miles, Easy, Heart Rate Zone 1
Monday PM: 6-8 Miles, Easy, Heart Rate Zone 1
Tuesday AM: 10 Miles, HIIT, Heart Rate Zone 4
Tuesday PM: Rest
Wednesday AM: 10-13 Miles, Easy, Heart Rate Zone 1
Wednesday PM: 5-8 Miles, Easy, Heart Rate Zone 1
Thursday AM: 18 or 24 Miles, Easy to Medium, Heart Rate Zone 1-3
Thursday PM: Rest
Friday AM: 10-13 Miles, Easy, Heart Rate Zone 1
Friday PM: 5-8 Miles, Easy, Heart Rate Zone 1
Saturday AM: 8-10 Miles, Fartlek (Tempo Runs), Heart Rate Zone 1-3
Saturday PM: 5-8 Miles, Easy, Heart Rate Zone 1
Sunday AM: 10-13 Miles, Easy, Heart Rate Zone 1
Sunday PM: Rest
Many participants in half marathons, full marathons, triathlons, or obstacle races, train completely differently, with the majority of their training consisting of long runs at medium to high intensity. However, if you want to improve your race results, you should be focusing on your aerobic capacity.
The human cardiovascular system uses three distinct but interrelated energy pathways to fuel your muscles. The anaerobic energy system is divided into alactic and lactic. The alactic system refers to the process of splitting stored ATP and phosphocreatine (PCr) for short duration explosive energy. Lactic system refers to breakdown of carbohydrate to lactic acid through glycolysis for high intensity output lasting under three minutes. The aerobic system refers to the combustion of carbohydrates and fats in the presence of oxygen for all of your other energy needs (8).
When your heart rate is below your aerobic threshold, your body will efficiently burn fat as energy and your pace can be maintained for a very long time. As you speed up, you will pass your aerobic threshold, and your body will start using both fat and carbohydrates for fuel. As you speed up further, you will hit your lactate threshold, which causes your body to switch to using depletable anaerobic energy sources that will eventually force you to stop or slow down (9).
As an endurance athlete, your goal should be to maximize your aerobic adaptations. First, you should train your zone 1 cardio as much as possible, which may be simply walking or jogging on a treadmill. One study found that untrained individuals increased their aerobic capacity when training based on aerobic threshold as opposed to VO2 max (10). Second, you should focus on keeping your heart rate low during your long runs instead of focusing on fast pace (11). Third, you should devote 10-15% of your training on high intensity workouts to improve your VO2 max, which can raise your zone 1 heart zone (12).