Hard days are hard, easy days are easy
Despite the simplicity of this message, polarised training is a topic that has excited, infuriated and baffled many amateur endurance athletes.
Popularised by top physiologist Stephen Seiler, polarised training has since been promoted in countless articles and books like 80/20 Running and 80/20 Triathlon by Matt Fitzgerald. However, despite the volume of material written on the topic, it remains a popular topic to debate on internet forums and seems to divide people like nothing else (apart from almost anything on Twitter).
Dr Seiler has published a series of papers that examine the training patterns of elite athletes across various endurance disciplines like cycling, running, skiing and rowing. He found a remarkably consistent pattern in the balance between easy sessions and hard workouts. Before we discuss what that pattern was, let’s establish a system for categorising workouts.
Three Zone Model
It’s common practice for endurance athletes to assign training zones to sessions in terms of power, pace or heartrate. The number of zones varies, often between 5 and 7, with rather complicated names like “anaerobic capacity” and “neuromuscular power”. Dr Seiler has helpfully simplified this to just 3 zones, which we’ll call “low”, “moderate” and “high”.
Unfortunately, these are defined by rather more complex physiological parameters that we could refer to by a number of different names. For the sake of argument, we’ll refer to them in terms of lactate as that’s what endurance athletes are most likely to be familiar with, even if they haven’t had a lactate test themselves. We could use ventilatory thresholds (VT1 and VT2), for example, but the discussion would be much the same.
Dr Seiler has helpfully simplified this to just 3 zones, which we’ll call “low”, “moderate” and “high”
When we exercise at low intensity, most of our energy comes from the aerobic metabolism, which doesn’t generate any lactate. This means lactate levels stay low, possibly even lower than at rest because we start to use some as fuel.
Zone 1 is defined as being below LT1 (lactate turning point 1), where lactate levels are no higher than at rest. It’s characterised by easy breathing, where you could comfortably hold a conversation. Think recovery pace and steady endurance work.
As effort ramps up, we start to rely more on anaerobic pathways that generate lactate to supplement our aerobic metabolism. This generates increasing amounts of lactate. In response, our body shuttles that lactate around and uses it as fuel and we see lactate levels in the blood start to increase. However, we’re still in control and lactate is being used as fast as it is generated.
In Zone 2, between, LT1 and LT2 lactate turning point 2), lactate concentrations are elevated in the blood but would stay constant if we stayed at the same pace. Breathing is a bit heavier but you might be able to speak in short sentences.
Eventually, we can’t handle all the lactate that is being generated and it starts to build up. Now the metabolic clock is ticking!
Zone 3 (high intensity) begins at LT2, which is pretty close to functional threshold power (FTP) or threshold running pace. It’s roughly the intensity we could maintain for an hour of continuous work. Anywhere above this point, lactate continues to accumulate in the blood and eventually we are forced to slow down. Breathing is heavy and you can only manage single words or short phrases, most of which might end in “off”.
Theory into practice
Using this three zone model, here are some typical sessions and where they would fit in this system:
The Polarised or 80/20 model
When Dr Seiler looked across different endurance sport, he found that elite athletes’ training had converged to a remarkably similar pattern - across the season, 80% of sessions were “easy” aerobic development and just 20% were “moderate” or “hard”.
I believe some of the confusion with polarised training comes from the early studies, which found that athletes were training almost entirely in zone 1 and zone 3, with very little work in zone 2. This led to the idea of zone 2 training as being a “grey zone”. Consequently, people argued that zone 2 training had no value and should be avoided at all costs. Later studies found that some disciplines (typically longer steady state efforts) favoured a pyramidal distribution, with more work in zone 2 than zone 3.
However, the one fact that remained constant across all studies was the high volume of zone 1 training – almost always around 80%.
Typically, longer events like Ironman triathlon might favour more time in zone 2, while a short event like a UK hill climb might benefit from a more polarised approach. The most effective strategy will also depend on the individual athlete, their athletic history and how they respond to different types of training.
Selles-Perez et al. (J Sports Sci Med. 2019;18(4):708‐715. Published 2019 Nov 19.) found, in their study “Polarized and Pyramidal Training Intensity Distribution: Relationship with a Half-Ironman Distance Triathlon Competition” found that a pyramidal training distribution (77.9%/18.8%/3.3%) with more time in zone 2 than in zone 3 was more effective than a polarised distribution (84.5%/4.2%/11.3%). However, note that the pyramidal distribution still involved 78% of training in zone 1.
An alternative to this is to focus training on intensities in the middle zone in the belief that zone 2 training, being harder, must be more effective than zone 1. This results in a threshold intensity distribution.
Is polarised training right for recreational athletes?
It’s fine for the pros, but I can’t be noodling around at easy intensity all the time. I need to get fit!
Pros have more time to train so accumulate a huge volume of easy aerobic training. Even a pretty dedicated amateur athlete (depending on the discipline) might only train 10 hours a week. Should you really spend 8 hours of that going easy? Wouldn’t you get fitter just training hard most of the time?
There have been a few studies that looked into this for trained (but not elite) runners and cyclists and the results suggest not.
Munoz et al (International Journal of Sports Physiology and Performance, 2014, 9, 265 -272. DOI: 10.1123/ijspp.2012-0350) found “Polarized training can stimulate greater training effects than between-thresholds training in recreational runners."
Neal et al (J Appl Physiol (1985). 2013;114(4):461‐471. doi:10.1152/japplphysiol.00652.2012) found “Six weeks of a polarized training-intensity distribution leads to greater physiological and performance adaptations than a threshold model in trained cyclists”
ok, so I’ll do some low intensity training. But what if I just throw in a few more high intensity sessions? A few is good so more must be better!
Billat (she of 30/30 fame) et al. (Medicine & Science in Sports & Exercise: January 1999 - Volume 31 - Issue 1 - p 156-163) looked at some trained endurance runners and found that they were able to increase running speed at VO2 max with a programme of 4 continuous (easy pace) runs, one high intensity (HIT) session, and one lactate threshold (LT) session. When they changed this and added intensity, with two continuous runs, three HIT sessions and one LT session each week they found no additional adaptive benefit, increased subjective training stress and indicators of overtraining.
All of which tells us that polarised training works for recreational athletes and there’s a limit to how much high intensity work you can and should do.
A typical week
Although the training plan for every athlete should be tailored to their history, goals and progression during the season, here’s a typical week that might result in a polarised 80/20 intensity distribution for a cyclist. The details would be different for a runner, but the principles would be the same. It includes some hard efforts, longer endurance rides and easy recovery days. The hard days are hard and the easy days are easy! It’s a sustainable, effective approach to training that could be repeated over and over, building on fitness gains over time like compound interest building up in your savings account.