The 80/20 model has become gospel in endurance sport. Eighty percent of your training easy. Twenty percent hard. Nothing in the middle. The reasoning sounds compelling: the middle zone is a no-man's land where you are too hard to recover from and too easy to produce high-end adaptations. Avoid it entirely, and you will get faster.
The problem is that this model was derived from elite athletes training 20 to 30 hours per week. When you apply it to age-group triathletes training 8 to 12 hours, something breaks. The zone it tells you to avoid is precisely the zone most likely to move the needle for you.
Where the 80/20 Model Came From
The polarised training model emerged from studies of elite endurance athletes, particularly cross-country skiers and distance runners. Researchers analysed training logs and found that the most successful athletes spent roughly 80 percent of their time below the first threshold and 20 percent above the second, with very little time in the zone between the two. This is similar to what the Norwegian endurance model is often reduced to in popular discussion.
This makes sense for athletes training at very high volumes. When you are doing 25 hours a week, you accumulate enormous aerobic stimulus from sheer volume alone. Your easy sessions are productive because there are so many of them. The high-intensity sessions provide the top-end stimulus. The middle zone is genuinely unnecessary because the volume of easy work already covers that adaptation.
Why It Breaks for Age-Group Athletes
Now take an age-group triathlete training 10 hours a week across three disciplines. Eighty percent easy means eight hours of easy training, split across swimming, cycling, and running. That is roughly two and a half hours per discipline per week at low intensity. For most athletes, that is not enough volume to drive meaningful aerobic adaptation through easy work alone.
The remaining 20 percent, two hours per week, goes to high-intensity work above the second threshold. That is valuable, but it leaves a massive gap. The entire zone between the first and second thresholds, the zone where tempo, sweet spot, and threshold work live, gets zero dedicated attention.
This is the zone where age-group athletes have the most to gain. Work between HRVT1 and HRVT2 - properly understood as sub-threshold training - drives aerobic development more efficiently than easy work alone, because it places a greater demand on the aerobic system per unit of time. For time-limited athletes, efficiency matters enormously. An hour of well-prescribed tempo work produces more aerobic adaptation than an hour of easy spinning.
The Pyramidal Alternative
A pyramidal training distribution still places the majority of volume below the first threshold. The base of the pyramid is easy aerobic work. But instead of jumping straight from easy to hard, it includes meaningful time in the zone between the two thresholds. Above that, it includes a smaller amount of high-intensity work above the second threshold.
The distribution might look something like 70 percent below HRVT1, 20 percent between HRVT1 and HRVT2, and 10 percent above HRVT2. The exact ratios depend on the athlete's profile, training phase, and event demands. But the key difference is that the middle zone is not avoided. It is used strategically.
Research supports this approach. Multiple studies comparing polarised and pyramidal distributions in trained but non-elite athletes have found that the pyramidal model produces equal or superior results. The athletes who include moderate-intensity work improve their thresholds, their race performances, and their efficiency metrics at least as well as those who avoid the middle zone entirely.
The Middle Zone Is Not No-Man's Land
The idea that training between the first and second thresholds is wasted effort comes from a misunderstanding of the original research. For elite athletes with massive training volumes, the middle zone adds fatigue without adding stimulus beyond what they already get from volume. For age-group athletes with limited hours, the middle zone is the most time-efficient way to develop the aerobic system.
Think about what happens physiologically in this zone. You are above the first threshold, which means your aerobic system is working hard to meet the energy demand. Lactate is being produced through glycolysis and fed back through the Krebs cycle as a fuel source, but at a rate that sits just above what can be fully oxidised in real time. Hydrogen ions and other metabolic byproducts accumulate gradually rather than exponentially. Mitochondrial density, capillary development, fat oxidation, and cardiac output are all being stressed meaningfully. These are exactly the adaptations age-group triathletes need.
Avoiding this zone because elite athletes do not need it is like avoiding strength training because marathon runners do not lift heavy. The context matters. What works for an athlete training 25 hours a week does not automatically apply to someone training 10.
How to Apply This
The first step is knowing where your thresholds actually sit. Without accurate HRVT1 and HRVT2 values, you cannot define the zones properly, and you risk doing your moderate work too hard or too easy. This is exactly why a single FTP number is insufficient - DFA Alpha1 testing gives you both thresholds from a single ramp test.
Once you have your thresholds, structure your week with the majority of volume below HRVT1, one to two sessions per week that include work between the two thresholds, and one session per week that includes efforts above HRVT2. The moderate sessions might be tempo runs, sustained cycling efforts, or threshold swim sets. The key is that they are prescribed at the right intensity for your physiology, not estimated from a percentage of FTP.
Over time, as your thresholds shift, the zones update. What was moderate becomes easy. What was hard becomes moderate. The training evolves with your physiology, and the middle zone continues to be where the most productive work happens.
The zone that polarised training tells you to avoid is the zone where age-group athletes have the most to gain. Do not leave it empty.