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Did Manon improve her fitness from JUST Zone 2 cycling training?

Everyone is talking about zone 2 at the moment. So, we teamed up with Manon Lloyd at GCN, to find out whether JUST low intensity training, maxing out at zone 2, can improve your fitness. What is it? Why could it be effective? How do you implement it? Read on to find out more...and if you're a little impatient, then scroll to the bottom to watch the video!

Training, like everything else in cycling, and sport, and the world, goes through trends. A few years ago HIIT was the new thing, then SIT, now there's a new training method being talked about, Zone 2 training. As always, there's nothing new here, with professional and amateur athletes alike having performed this type of training for centuries. But, what exactly do we mean by zone 2 training? And, can training just at this intensity lead to improvements?

Well, we teamed up with Manon to find out. Manon completed 6 weeks of training, involving just Zone 2 training. If you haven't seen the first video, then check it out here

Zone 2 training: What is it?

Zone 2 itself, isn't really a thing. Different sports, coaches, governing bodies etc, use different training zones to prescribe their training. Zone 2, refers to the second zone of a 5 (or perhaps 8 even) zone training model. Using a 3 zone model, it would be referred to as Zone 1. So, really, describing it as zone 2 is a bit misleading as it could mean very different things.

So what should we term it instead? Really, we should just call it what it is; low intensity training. The top of this zone is the lactate threshold (LT), which is the first distinct rise in blood lactate concentration observed in a step test. So, zone 2 training refers to training BELOW the lactate threshold; here heart rate, perceived effort, blood lactate concentration, oxygen cost are all steady, you can ride holding a conversation, and it is the duration, not the intensity that tires you out.

Using the picture above, we shouldn't get too hung up about whether we're riding in zone 1 or zone 2, as in essence there is no physiological difference to the two zones. Indeed, riding further towards the top of zone 2 doesn't lead to greater endurance adaptations (see Granata et al, 2018, for a highly detailed review of this), and typically going longer (i.e., at a lower intensity), and accumulating more time per day, week, month, leads to better adaptations than going a little harder.

So, zone 2 refers to low intensity training below the lactate threshold, where you can hold a conversation, and the duration not intensity, is what tires you out.

So, did Manon train here?

Absolutely! We set Manon training sessions that moved intensity below and up to the lactate threshold. Training at the top of zone 2, close to lactate threshold, all the time is far too tiring. In fact, our Olympic and professional athletes would typically average an intensity around 10-15% less than this, with time across recovery, zone 1 and zone 2. So, you can see, using all the freedom of below lactate threshold is key.

So, for heart rate, Manon spent almost 50% of her training in zone 2, with another 46% below this intensity, and only 5% above this. For power, of course there is more time in all zones. You have to hit higher powers moving from traffic lights, from junctions, to not fall off going up hills, and similarly freewheel, descending, riding easy, will accumulate power in lower zones. This is a huge amount of time at lower intensity, and absolutely shows Manon did a great job with her training intensity discipline.

Looking at the 3 zone model, you can see, almost 95% of training was spent below the lactate threshold, demonstrating Manon's discipline beautifully! Does a little time in higher zones matter? Absolutely not! Over a 2, 3, 4 hour ride, you're going to accumulate time in all zones. Take a look at peak heart rate/ power for duration, and this tells a better story of how hard you actually went.

We gave Manon variety. For example, one day was a free-ride, to go and enjoy time in the saddle, explore new routes, and enjoy riding your bike without thinking about it. Another, included mid zone 2 efforts, at a prescribed heart rate, accumulating long blocks at this intensity. Another ride had efforts at the top of zone 2. These were shorter, as if held for too long would turn in to zone 3 blocks, but moving intensity around zone 1 and 2.

What happened?

Photo: globalcyclingnetwork, instagram

Manon had a great response to this training! We always think, whats the minimum training stress required to bring about a response. Increasing duration of low intensity training is the first level. For Manon, this meant she could enjoy her training, she had motivation, it wasn't scary, she couldn't "fail" on a turbo session that was too tough, which meant she completed 100% of a training set. That's the key here; Manon wanted to get on the bike and train, and reaped the rewards.

Blood lactate response

The blue lines show the blood lactate concentration (lower) and heart rate (higher) for each stage of the step test done at baseline, before Manon started training. The red lines, shows this after the 6 week training block

So, looking at the lower lines the red line is lower, and flatter, meaning significantly less blood lactate is accumulating at all intensities, and a really typical response to low intensity training; a flattening or lowering of the blood lactate curve. This really is a textbook response, and shows significant metabolic, or peripheral adaptations in Manon's muscles, likely with an increase in mitochondrial (where energy is resynthesised) number, size and density, and more capillaries (allowing blood flow and gases to exchange).

LT, and LTP have both moved on by around 20 W. Other typical markers we look at are the power at 2 and 4 mM. Again, these have shifted on really well, and shows a great response to this block.

What's to note, is that towards the end of this training block, if Manon was using ONLY power to guide her training, she'd be close to riding at 20 W easier than at the start of the block! This is why power isn't a great marker to use; we refer to this as an external marker of intensity, and it must be used with internal markers, such as blood lactate concentration, heart rate, or our favourite, rating of perceived effort (RPE). Interestingly, RPE post-training isn't too different from pre-training in this assessment. This might however, be due to residual training fatigue in the post-training test, whereas for the pre-training test Manon was "fresh" having not done any training at all!

Heart rate

Although a small difference, heart rate is lower in the post-training test by around 5 beats/ min. This shows cardiovascular adaptations, with an increase in heart size, due to a small increase in blood volume, leading to more blood being ejected from the heart in each beat.

This isn't unexpected, but typically thought about as being an adaptation to higher intensity training. But, this shows, whilst we think about adaptations being linked to specific intensities, it's not really as clear cut as that. Low intensity training will bring about all adaptations, up to a point, then a different overload is required to further responses.

Top end responses

Maximal oxygen uptake (VO2peak) increased by around 7.5%. Maximal oxygen uptake is closely linked with blood volume (and hence stroke volume and cardiac output), so the associated decrease in sub-maximal heart rate goes hand in hand with this.

What's more important than this, is the power at maximal oxygen uptake, and this increased from 263 W to 295 W, a whopping 12% improvement! This is great, and shows adaptations across the whole intensity spectrum; with increased speed and power for efforts lasting just a few minutes up to a few hours!

Was this expected?

Absolutely! Training is all about creating an overload. For Manon, she was motivated to train, had accountability (as I wrote her some training!), so jumped on her bike and trained. That resulted in overload. Overload can be riding more frequently, longer, or harder. So the first question is always, what's the minimum stimulus required to bring about adaptation?

Sure, if Manon did exactly the same training for another 6 weeks, improvements would be small, or non-existent. But, that doesn't mean high intensity training is required just yet. With a UCI world tour rider, I once prescribed 6 weeks of low intensity training; and he got huge results!

Was this the best programme?

Does it matter? Will we ever know? No, is the correct answer to both of these questions. The best programme is the one that inspires you, excites you, motivates you, to get out, exercise and love what you're doing! If that's riding for a long time, exploring new places, speaking with friends, and naturally training at low intensity, then great. And if that's going to the hurt locker every day, pushing your limits with intensity, then knock yourself out.

For most of us, we want to train, enjoy ourself, and feel good. Not riding your bike doesn't achieve that; so whatever gets you on your bike with a smile (or grimace!) on your face is the best thing for you.

Of course, if you're looking for performance, or to tear up the Sunday club run, or win the Olympics like some of our riders, then there are more effective ways than others. This is something something we feel we have significant expertise in through our backgrounds in high performance, elite and professional sport, working with some of the best athletes and coaches in the world, and our own practice and research


Training at all intensities is probably the best thing you can do for performance, and a structured plan will help you to achieve success. If you want to get fit, feel good, and enjoy yourself, then getting out on your bike more often, with a smile on your face, at low or high intensity, is going to get you a long way.

Watch Manon test and discuss results here...

Question? Comments? Please leave a comment below to share your thoughts!

Happy training at whatever intensity you choose.

Dr Laurence Birdsey

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