Understanding the ‘training domains’

Before we go into polarised training specifically, first we need to understand the ‘training domains’.

You may remember that in previous coaching articles we’ve looked at training zones. The basic idea is that riding at different intensities stimulates different adaptations in your body. It’s quite obvious, really – doing long base miles doesn’t make you a better sprinter – and by using training zones you can target different areas of fitness.

As a result, whether you use a coach or write your own training plan, you will use different zones to bring about different adaptations, whether you’re looking to increase your threshold, improve your sprint or build your endurance.

However, the training zones you see on Training Peaks and Strava are actually based on a three-domain model, based on your body’s physiological response to exercise.

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The domains are referred to as moderate, heavy and severe, and physiological thresholds separate these three domains. You may have actually heard of lactate threshold – but there are, in actual fact, two lactate thresholds.

The first lactate threshold is at the power output at which we see a rise in blood lactate levels above the level at rest. The second lactate threshold is the maximum power you can sustain without blood lactate levels getting out of control – the level you may have previously have heard referred to as threshold. Go any harder and blood lactate levels will continue to rise even if power remains constant and eventually you won’t be able to sustain that power output.

Why is polarised training better than other training models?

This is the golden question, of course – and one which has been the subject of a lot of research. Almost unequivocally, studies have shown that athletes following a polarised training model have seen bigger benefits than those following a threshold model.

Why? Let’s get into the science. It all comes down to what stimulates your body to adapt to training. When you exercise, your muscles produce a lot of different substances called metabolites which build up and make your muscles less efficient as exercise continues.

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As you probably know already, your brain sends electrical signals to your muscles to tell them to contract, but these metabolites interfere with these process. However, at the same time, it’s these very metabolites which your body uses as a signaling method to stimulate physiological adaptations.

The thresholds that separate the training domains essentially represent different levels of these metabolites and your body’s response to the increase in these metabolites is to produce lactate. In turn, this releases energy which is used to process the metabolites produced – that’s right, lactate is actually helping you perform not hindering your performance!

Therefore, the harder you ride, the higher the level of metabolites and the more lactate your body produces. Now, your muscles have a limited capacity to deal with lactate and therefore the excess is pumped away in the blood to be dealt with elsewhere in your body – the very reason why blood lactate levels rise.

The first lactate threshold represents the power output at which the muscle cells need to produce more lactate than it can process, and therefore it ships it off in your blood stream and we see a rise in lactate levels.

The second lactate threshold represents the point at which there is a delicate balance between the amount of lactate being produced by your muscles (to deal with the metabolites being produced) and the amount the rest of your body can process. If the muscles produce any more lactate then the rest of your body cannot keep up, so the input of lactate into your blood is higher than the amount being processed.

Considering that we need to produce metabolites in order to give our body the stimulus to adapt and improve, then it makes sense that we should be training in the domain which produces the greatest quantity of metabolites – or, in other words, the severe domain.

You are undoubtedly aware that in order to improve. you need to overload your body – i.e. exercise harder than you are used to. This process holds true all the way down to a cellular level. Exercising in the severe domain does this by overloading your muscle cells with more metabolites and lactate than they can deal with, but it also stimulates the muscle cells to become more efficient, producing less metabolites for a given power output, and increasing the amount of lactate they can process.

It sounds like I’m neglecting the heavy training domain?

You are, really, and there are two reasons for this.

1. Training in the heavy domain is very tiring, so when you come to do your important intervals in the severe zone, you just can’t hit the numbers you need to in order to get the biggest adaptations.

2. The second reason comes down to something called the ‘slow component’. This is a complex physiological issue – but essentially, as you continue to exercise in the heavy domain, you become less and less efficient.

As a training session, continues, you have to supply your muscles with more and more oxygen, so heart rate goes up and breathing rate goes up. You might think ‘great, this means I’m working harder’, but it’s not quite that simple.

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You are becoming less efficient because your muscle cells are becoming fatigued. In response, you body uses more and more muscle fibres to produce the same amount of power. On top of this, your body is relying on more fast muscle fibres, converting them into slow-twitch fibre over time.

Therefore, a lot of heavy zone training will mean you can ride hard all day but won’t have anything when it comes to riding really quickly or sprinting – and ultimately that’s where races are won and lost. Chances are, you will know a rider who fits the mould.

Great – I’m in! How can I implement a polarised training plan?

As I mentioned at the top, to follow a polarised a plan you need to spend 80 per cent of your training time in the moderate domain and 20 per cent in the severe domain, all the while minimising the amount of time in the heavy domain.

We aren’t all lucky enough to be able to undertake lactate testing so how can we know what training domain we are in? This is where your training zones come in – you can use these to estimate your training domains.

Roughly speaking, if you are using the five-zone system, the top of zone two aligns with the first lactate threshold. You then need to minimise the amount of time in zone three and the bottom half of zone four as they correspond with the heavy domain. FTP power and higher corresponds with the severe domain.

There are also a number of other things you need to watch out for if implementing a polarised training plan. First of all, you will need to do at least one long ride a week. The adaptations brought about by training in the moderate domain only really take place when you spend a prolonged period at that level – you’re looking at three hours for now. The rest of the week is then spent exercising in the severe domain, sometimes even using sessions as short as 20 minutes to fit in with the busy lifestyles many of us lead away from the bike. Therefore, you could use your weekend ride for moderate training, and short but intense midweek sessions for severe training.

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In addition to this, when you first start a polarised training plan you may find that riding easy enough to stay within the moderate zone is difficult. It can be frustrating as you find yourself creeping into the heavy domain with little effort, wondering whether riding this easy is actually of any benefit.

In my experience as a coach, it takes roughly six weeks of following a polarised plan before you start to see real benefits. It’s during this period that your body’s response to exercise is reprogrammed.

Coaches have found that when an athlete who has traditionally trained using a threshold model of distribution starts a polarised plan, the intensity they have to ride at to stay below the first lactate threshold is very low. However, after roughly six weeks of following the new plan, the athlete’s lactate profile will have changed and power output at the first lactate threshold will have risen considerably. From this point onwards it is much easier to stay in the moderate domain and truly get the most out of a polarised training plan.

Now all that’s left is to put everything into action. If you’re wondering what a polarised training plan might look like, here’s an example based on a cyclist who rides four times a week.

Example training plan