Cycling Intensity deep dive: The Importance of intensity discipline in achieving your potential on the bike

The bunch cresting the infamous Ryals at the Curlew Cup Nat A 2021 – An example of an event that requires you to get your training intensity right!


For my second blog, I’ve decided to get down into the knitty gritty of cycling training and tackle what I believe is the least understood and most misused component of cycling training plans: intensity. I’ll cover how we measure intensity in cycling, why we use training intensity to improve performance, what common mistakes athletes make when including intensity in their training plan and then finally I’ll look at how you can apply all of this to your training programme to achieve your potential in the sport.

The Basics: What is intensity and how do we measure it?

As I’m sure you all know, simply put, intensity is how hard you are performing an activity. For cycling, there are two main ways that riders without access to a sports physiology lab can objectively measure and quantify their training intensity. The first of these is the power meter, which quantifies the workload a rider is performing. The second is the heart rate monitor, which reflects how hard a rider’s physiological systems are working to perform a given external workload (power). As a result, using the two in combination gives coaches and athletes an objective insight into the internal stress that a workload causes in an athlete and therefore how their fitness is changing over time.

Running Through the Basics: How do you individualise intensity to each rider’s ability?

Every athlete has a different ability to produce a given power because of their different physical capacities. For example, many world tour athletes will be able to produce 150W with a heart rate of less than a 100bpm whereas some newer cyclists may struggle to even produce 150W for an hour. Simply put, this is because a pro cyclist is more efficient at producing power because of a combination of physical adaptations made through training, often combined with natural genetic talent. The most important measures are maximal oxygen uptake (VO2 max), lactate threshold and aerobic efficiency – which is the amount of oxygen a rider requires to produce a given power output (Hans-Christer Holmberg 2012). The individual variation of these characteristics means that training zones and power targets must be individualised for each rider when putting together their training plan. This is usually done through calculating a riders Functional Threshold Power (FTP). I won’t cover in detail the different ways this can be done (maybe that’s for another blog piece) but most importantly, once calculated, FTP acts as a rough estimate for the highest power an athlete can sustain for an hour.

Training to Power Zones: A brief overview

So, what do we do once we’ve calculated a rider’s FTP? The most used training zones are Andy Coggan’s 7 zones, which reflect the individualization of power between athletes and range from active recovery to neuromuscular power:

Figure 1 – Andy Coggan’s 7 Power Zones

We can learn how performing work in these zones affects our body through looking at Andy Coggan’s et al’s expected physiological adaptations table. This gives us a rough outline as to how riding at different intensities gives our bodies the adaptive signalling it requires to cause different physiological adaptations:


Figure 2 – Hunter Allen and Andy Coggans expected physiological adaptations for Training in each zone. (Allen et al., 2019)

The table shows us that you see the greatest physiological adaptations an athlete will gain occur when training is performed between zones 3-5. So, the rational question might be ‘why don’t we just perform all training in these higher zones?’ Anyone that has ridden bikes will intuitively know that the fatigue from spending excessive durations in zones 3 – 5 day after day, makes this impossible. This can be confirmed by looking through any pro cyclists Strava feed and looking at the crazy volumes of relatively low intensity miles that they put in. My personal favourite is Egan Bernal. He regularly goes out for over 6 hours and averages 150W, a pace that the vast majority of amateur cyclists would consider easy:

Figure 3 – Egan Bernal’s Power zone distribution from his training ride on 30/12/21

The most common response when I show people that one of the world’s best endurance athletes spends a large amount of his training time in Zone 1 is ‘why on earth is he doing that? Surely that’s too easy to produce a beneficial training response?’. These exact questions are what I’m going to look to answer in the rest of this blog by delving into the science.

To do this I am going to turn to the works of Dr. Stephen Seiler (2010) who is the founder of the term ‘polarized training’. He has spent much of his career researching endurance training and has c.7500 citations to his name. Much of his work has focussed on looking at the human stress response to training, rather than just the adaptive signalling produced which led to him creating a simplified training zone model that is based on the physiological stress responses that he saw when endurance athletes exercised at different intensities:

Figure 4 – Stephen Seiler’s 3 zone training model of exercise intensity with blood lactate shown on the Y axis (Seiler 2010)

Zone 1 represents endurance training or ‘all day pace’. Seiler quantifies this as the pace below that at which blood lactate begins to rise. This is quantified as a blood lactate of less than 2mmol, which signals that the working muscles are receiving adequate energy purely from aerobic respiration. The top of this zone roughly matches the top of Zone 2 on Coggan’s 7 zone training model so, for practical purposes, the two can be thought of as the same. The middle zone of Seiler’s model; ‘Zone 2’, ranges from this point to the line marked ‘MLSS’. MLSS simply stands for ‘maximal lactate steady state’ or the highest pace you can hold without producing more lactic acid than your body can buffer without fatiguing rapidly which is more commonly known as FTP amongst cyclists. Everything above MLSS is termed ‘Zone 3’ by Dr Seiler which represents the top of zone 4, as well as zones 5,6 and 7 of Coggan’s power zones.

Looking at the stress response of training at different intensities and how you can use this to apply intensity correctly to your training plan

Now we have looked at the adaptive signalling of exercising in different training zones it’s time to look at the stress responses time in them produces so we can determine how they should be included in your training.

The stress response produced by training is controlled by your autonomic nervous system which controls involuntary physiological processes including:

  • Heart rate
  • Heart rate variability
  • Breathing rate increases
  • Core temperature
  • Blood pressure
  • Extra oxygen is sent to the brain and senses become sharper
  • Glucose and fatty acids are released into the blood stream from temporary storage sites.
  • Cortisol, adrenaline and other hormones are released.

Any athlete who’s done an intensive session before will have noticed that biomarkers such as heart rate and core temperature will remain elevated for an extended duration afterward. What Dr Seiler discovered through performing studies on how well-trained athletes respond to exercise intensity is that if an athlete performs all their training in a session in Zone 1, (Zones 1 & 2 the traditional 7 zone model), they see a rapid recovery of their sympathetic nervous system balance. However, the top of zone 1 ‘demarcates a clear threshold for ANS recovery’. In simple terms, this means that the time taken to return to normal ANS balance (HRV recovery etc.) doesn’t differ between Tempo training and VO2 max training. As a result, if a rider goes above that first lactate turn point in a ride they will disrupt their ANS balance in a similar way, regardless of the quality of the session. As Seiler describes, going above this turn point more than 2-3 times a week has no adaptive benefits and tends to induce symptoms of overreaching/overtraining. This illustrates the importance of intensity discipline on endurance rides; regardless of the quality of the session, if you go above the top that first lactate turn point, it stresses your body in a similar way that a quality VO2 max session does. If you do this on your endurance rides, on top of your 2-3 interval sessions a week, it gives your body no time to return to a resting ANS balance. If you do this for an extended period of time, regardless of your fitness and riding experience, you will overtrain.

In this piece, I’ve illustrated the importance of intensity discipline to help you reach your potential on the bike, particularly on days when endurance riding is the prescribed training session. If you wish to discuss how I can help you apply this and other training principles that underpin successful cycling performances don’t hesitate to get in touch at From there we can arrange a phone call and discuss how we can work together to design your training to make 2022 your best season yet :-).


Holmberg, Hans-Christer. (2012). Determinants of performance in endurance sports.

Allen, H., Coggan, A. and McGregor, S., 2019. Training and racing with a power meter.

Seiler, S., 2010. What is best practice for training intensity and duration distribution in endurance athletes. Int J Sports Physiol Perform5(3), pp.276-291.


















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