Tour de France champions swear by Zone 2 training, but making it work for the Average Joe is not so simple.

The Zone 2 idea has exploded in the past couple of years, with countless YouTube videos and articles written about the benefits of low-intensity training.

Put simply, Zone 2 is the metabolic state where you burn the most fat to power your exercise. It's also a zone where it's easy enough to exercise for a long time without blowing up.

The Zone 2 idea is that low-intensity training should make up the bulk of your training volume and by doing this you'll increase your overall cardiovascular fitness without having to smash yourself.

It's in direct contrast to the concept of high-intensity training and interval training, which were all the rage for a time, particularly for time-poor people.

The idea being that short, sharp, high-intensity sessions could make up your entire fitness regime.

One of the biggest proponents of Zone 2 is Inigo San Millan, a professor in Colorado University's Department of Family Medicine, who specialises in physiology, metabolism, mitochondria and cancer research.

Dr San Millan is the director of performance with UAE Team Emirates, the cycling team of two-time Tour de France winner Tadej Pogačar.

Dr San Millan says Pogačar will spend about 80% of training at Zone 2 and he says that should be the same for all of us.

What exactly is Zone 2, how does it work, and just how easy is it?

In order to answer that question I subjected myself to an experiment.

My guide is Antony Stadnyk (Above left), a lecturer at the School of Sport, Exercise, and Rehabilitation at the University of Technology Sydney, and a former physiologist with the New South Wales Institute of Sport's cycling program.

"So this is what we for a long time have called the aerobic endurance training zone," Dr Stadnyk says.

"It's got this fancy new name, Zone 2, but it's basically the top end of the low-intensity training zone.

"So it should feel easy, you should be able to have a conversation, but towards the top end, that's when you'll start to lose that ability and need to talk in shorter sentences or a couple of sentences before taking a breath of air.

"Zone 2 and our base conditioning, the aerobic base conditioning, is really the foundation of all our training."

Dr Stadnyk and I are talking after he's performed a series of tests on me to determine my metabolic thresholds and VO2 Max.

We did the tests in October last year.

My experiment is to commit to an extended block of training – the bulk of it in Zone 2 – to see if I get fitter and build my endurance.

I need a goal, so I've committed to riding in the Snowy Classic – a Gran Fondo in the Snowy Mountains.

There's a 170-kilometre version, which I think is going to be a stretch too far for me – this year at least – so I'm doing the 107km loop from Jindabyne, which takes in around 1,500 metres of climbing.

Back to the tests — I'm at UTS with my bike on a stationary trainer wearing a heart rate monitor.

Dr Stadnyk's strapped a mask over my head to capture the amount of oxygen I'm breathing in and carbon dioxide I'm exhaling.

After a warm-up, he asks me to ride for three minutes at a particular power output – which is measured in watts.

Dr Stadnyk is capturing all my data in real-time and has made a small pin-prick in my ear to collect a blood sample to measure my lactate levels as I go.

Then I'm off and pedalling.

Dr Stadnyk starts me off at a leisurely 80 watts and then every three minutes he asks me to increase my wattage by 20.

Each time I go up in power, he takes a blood sample to measure my lactate.

It's pretty easy at first of course, but after 24 minutes I'm at 220 watts and my heart's beating at 153 beats per minute (bpm) – about 91% of my maximum heart rate.

I could go for a bit longer, but Dr Stadnyk now has enough information to determine my various metabolic zones.

And for the data nerds out there, this is what a moderately fit and slightly overweight 56-year-old is pumping out.

After I take a breather, I warm up again for an all-out three-minute effort, which Dr Stadnyk is going to use to determine my VO2 peak and maximum heart rate.

At least it was meant to be a three-minute effort, but I made the mistake of going out far too hard and then had to hold on for dear life, while Dr Stadnyk quickly recalibrated it to a two-minute effort.

I've recorded an average wattage of 322 but he warned I should be cautious about the wattage because it was only a two-minute effort – which meant it was mainly anaerobic.

He estimated that I would have averaged around 265 watts if I continued for another minute. Next time around I'll go for a more paced three-minute effort and expect a lower mark.

But at least now he has the numbers. My VO2 peak was 45.6 and my maximum heart rate was 169bpm. I'm hoping that at the end of my training block, the VO2 peak, at least, will be higher.

Dr Stadnyk determined that my Zone 2 is somewhere between 115-130bpm or between 130-160 watts.

Ideally, we'd be using power as a metric during my rides, but I don't have a power meter on my bike, so I'm going on heart rate alone.

He came to those numbers by looking at both my lactate and ventilatory responses. You can see that above 120bpm and 140 watts, my lactate levels jumped from one millimole per litre (mM) to 1.5mM. There's another big jump after 130bpm and 162 watts to 2.4mM.

This graph bellow shows that while my heart rate steadily increased in a straight line with my wattage output, the amount of lactate I was producing increased slowly and then started shooting up at that 162 watts mark – an indicator that I'm starting to burn more carbohydrate and less fat.

So, what exactly are we talking about with all this lactate, heart rate and zone stuff?

Remember that during Zone 2 we're in the metabolic state where we are burning the most fat to fuel our oxygen.

"So, what we have is free fatty acids floating around the body, in the blood," Dr Stadnyk says.

Those fatty acids are converted by the mitochondria in our cells into Adenosine triphosphate or ATP.

"ATP is what our body uses to produce the actual muscle contractions and physiological processes that we need to sustain life," Dr Stadnyk says.

Now, at Zone 2 and below, our exercise intensity is such that the mitochondria can keep pace with our energy demands – burning fat consistently to keep powering our exercise.

Dr Stadnyk explains that when we consistently exercise in Zone 2, over time we get an increase in the number of mitochondria, which means our bodies become more efficient and have a greater capacity to oxidise fat for fuel.

We've been talking a bit about mitochondria, so Dr Stadnyk is taking us back to school:

"Probably back in high school, you've heard of mitochondria referred to as the powerhouse of the cell — that is absolutely true," he says.

"So the greater density and number of mitochondria that we have, the sort of fitter and healthier the system is."

So to summarise: As we train more in Zone 2, we produce more mitochondria, which means we have a greater ability to metabolise fats.

As we become more oxidatively powerful, our bodies can use fat for longer and put off using carbohydrates as a fuel source, saving those stores for when we really need it during high-intensity efforts.

So in theory, the lactate curve in the graph below should shift to the right as I become fitter, but that can only last so long once we start to increase the exercise intensity Dr Stadnyk explains:

"While fats are really energy dense, they can't be oxidised at a rate that is fast enough to maintain that exercise," he says.

"The top end of Zone 2 is what we call the first metabolic threshold — you might hear that referred to as lactate threshold one, or the ventilatory threshold one.

"And that represents the point where we start to have an increase in energy being provided by carbohydrates, which provide less energy [per unit], but can be oxidised at a faster rate.

"And so with that, we start to get an increased production of lactate."

Zone 3 is what Dr Stadnyk calls a tempo zone – we're starting to work a bit harder, and often you'll find yourself drifting into this zone during bunch rides.

"And then above that, we go into our threshold zone – Zone 4 and that crosses the second metabolic threshold," he says.

"And what that second metabolic threshold represents is where we are going predominantly into anaerobic metabolism, so we're not supplying enough oxygen to continue to fuel exercise."

You can see from my data that this happened to me at 200 watts where my lactate jumped from 2.4mM to 4mM.

Zone 3 is what Dr Stadnyk calls a tempo zone – we're starting to work a bit harder, and often you'll find yourself drifting into this zone during bunch rides.

"And then above that, we go into our threshold zone – Zone 4 and that crosses the second metabolic threshold," he says.

"And what that second metabolic threshold represents is where we are going predominantly into anaerobic metabolism, so we're not supplying enough oxygen to continue to fuel exercise."

You can see from my data that this happened to me at 200 watts where my lactate jumped from 2.4mM to 4mM.

Zone 4 is what's sometimes called threshold – it's hard work.

If you've ever tried to run a personal best at Parkrun, you would have been running at your threshold – although you would find yourself in the zones 5 and 6 as you pushed towards the end.

Zone 4 is when you're on the red-line, staying just short of the level of exertion where you would burn out in just a few minutes if you upped the intensity.

How long can you stay at the threshold? Again, it depends on training – for me it might be 30 minutes, but an elite cyclist or runner could go for much longer.

As Dr Stadnyk says: "We know the benefits of aerobic endurance training, we have decades of evidence to show that it works.

"Get out and do exercise really, every little bit counts. It's definitely worthwhile spending a large volume of time at the lower intensity."

But he also says there's a benefit to doing a bit of work in all your power zones so you get the adaptations at both ends.

And that's what I'm going to do. I'll continue to do most of my riding at Zone 2 but be sure to put in some harder efforts on at least one day a week.

And above all, I'm going to keep riding.

Original Story By | David Mark