How much should you run easy and how much hard? Scientific research, including my own on the U.S. Olympic Marathon Trials qualifiers, has shown that elite runners run 75-80% of volume at low intensity (below acidosis threshold) and 20-25% high intensity (at and above acidosis threshold).
But, hold your monkeys! 🙉 When calculating intensity as a percentage of distance, time, or runs per week, the percentage of low-intensity is ALWAYS going to be much greater than the percentage of high-intensity. That’s because of the inverse relationship between volume and intensity. 80/20, which is based on elite athletes who train 10-15 times, or 10-25 hours, per week, really is an artifact of the inverse volume-intensity relationship rather than a true reflection of how runners train. When someone trains a lot, the majority of training is consequentially skewed toward low intensity. It’s simply not possible to do as much high-intensity training as low-intensity training.
Before you run 80% easy and 20% hard, it’s a mistake to copy what elite athletes do. Although elite athletes are very successful doing that, that doesn’t mean everyone should train that way, or that those athletes wouldn’t be even better if they trained a different way. Very few studies have experimented with different training methods to test which method is better than another method.
Also, the superior physiology of elite athletes enables them to get a lot of value from a low intensity. For example, running 80% low intensity may be enough of a stimulus for elite runners to adapt, but may not be enough of a stimulus for you. For elite athletes with a high VO₂max, a low intensity still generates a large volume of oxygen delivered to the muscles (called “oxidative flux”). Thus, an elite runner training easy at 60% of his/her VO₂max of 70 ml/kg/min (about 75% max heart rate) would have similar muscle oxidative flux as a recreational runner running at or near his/her VO₂max (0.60 x 70 = 42 ml/kg/min). In other words, an elite runner can achieve a similar muscle oxidative flux (which is translated into a similar signal for adaptation) at a much lower intensity than can a recreational runner.
So, what do you do? Well, that’s covered in my next book. 📖 😉 For now, run a lot at low intensity and increase the amount of high intensity throughout the year as you get closer to your target race.