How To Build Anaerobic Power & Stamina For Cycling
There are three systems that are used to produce energy during exercise: the aerobic energy system, the anaerobic glycolytic system, and the creatine phosphate (CP) system.
These systems operate at different speeds and with differing capacities. For example, the aerobic system produces energy the slowest (i.e. a lower power), but with a virtually unlimited capacity to sustain energy production during exercise. Whereas, the CP system produces large amounts of energy very rapidly (i.e. the highest powers), but with the capacity to power exercise for only a few seconds.
Sitting between these two systems is the anaerobic glycolytic system, which for brevity, we’ll call the ‘glycolytic system’. This is the main system used during all-out exercise lasting between around 30-seconds to 2-minutes, although it is also employed to a lesser degree over shorter and longer durations. For example, even during a 20-minute time-trial, which is classically used to measure the aerobic system (specifically FTP), there will be a notable contribution from the glycolytic system.
While the CP system does contribute to energy production during cycling, for most disciplines the major source of anaerobic energy comes from the glycolytic system, and so we will focus on this system in particular within this article.
The glycolytic system is important for disciplines requiring high power output over short durations, whether over a single effort (such as in hill climbs), or over repeated efforts (such as in criterium, cyclocross, MTB XCO and road racing).
As we’ll come onto later in this article, the glycolytic system (or more specifically the balance between the glycolytic and the aerobic system) is also important for longer, more steady-state disciplines such as time trials and sportives/gran fondos. So, it’s an aspect of training that everyone should be conscious of, irrespective of discipline.
In this article, we‘ll begin by explaining what the glycolytic system is and how it can be measured. We will then go on to explain the important relationship between the glycolytic and aerobic energy systems, and how this impacts the way you should train the glycolytic system. Finally, we’ll present some workouts you can use to develop the glycolytic system.
How The Glycolytic System Works
The glycolytic system produces energy when carbohydrates, in the form of glycogen (in the muscles or liver) or glucose (in the blood), are broken down into a substance called ‘pyruvate’, as shown in the figure below.
Flow diagram illustrating the relationship between the aerobic and glycolytic energy systems, and their respective end-products.
This process releases energy (in the form of ‘ATP’) and some other metabolites.
From this stage, the resultant pyruvate can have two fates. Firstly, if there is sufficient oxygen, the pyruvate can pass into the aerobic energy system, producing energy, water and carbon dioxide. This is the ‘ideal’ scenario, because this process produces only benign by-products (water and carbon dioxide).
Alternatively, if there is not enough oxygen to process the pyruvate, then the pyruvate combines with a hydrogen ion (and a molecule of NADH) to produce lactic acid. This lactic acid (itself a neutral molecule) quickly disassociates to form a lactate anion (i.e. negatively charged molecule), a hydrogen ion (H+) and an NAD+ ion.
While the mechanisms surrounding fatigue in exercise are still unclear, there is good evidence that at least some of the metabolites that are produced alongside lactate are linked with the onset of fatigue. It’s now thought that this fatigue is brought on through signalling to the central nervous system that a metabolic steady state has been exceeded, rather than via inhibition of muscle contraction directly (e.g. due to acidity caused by the H+ ions).
In any event, it’s clear that an excessive accumulation of lactate and associated metabolites does contribute to fatigue, and thus the glycolytic system is one that we might want to moderate use of during certain cycling disciplines.
Assessing Anaerobic Capabilities
Having understood the glycolytic energy system, this leads us to the question of measuring the capabilities of the anaerobic systems. There are a few aspects to this, as we’ve tried to illustrate in the following figure.
It should be noted that there is no standard terminology for these different concepts, and you will see the same words used to refer to different concepts in scientific and training literature, which can be very frustrating!
Diagram showing the components of anaerobic capability: the anaerobic power, anaerobic stamina and anaerobic capacity.
A first aspect – referred to as anaerobic power - is the maximum rate at which energy can be produced via the anaerobic system. This is made up both of energy produced via glycolysis and via the CP system, and these respective anaerobic abilities can be referred to as ‘glycolytic power’ and ‘alactic power’ respectively.
A second aspect – which we refer to as anaerobic stamina - relates to how long anaerobic metabolism can be maintained. Over durations lasting >10-seconds, this is almost entirely dependent on the glycolytic system and depends both on how quickly pyruvate/lactate can be cleared (thereby removing fatiguing metabolites), and how well high levels of fatiguing metabolites can be tolerated. As demonstrated in the figure below, the anaerobic stamina can be extended by riding at a lower, but still anaerobic power, so it’s not a fixed parameter.
Diagram showing the relationship between anaerobic stamina and power. As the power decreases, anaerobic stamina is extended, where the total anaerobic capacity dictates how long an anaerobic effort can be sustained.
Finally, a third aspect – which we’ll call the anaerobic capacity (sometimes referred to as anaerobic work capacity or the functional reserve capacity, although there is a subtle distinction between these terms) – is a measure of how much total energy can be produced via the anaerobic systems.
There are three key tests that can be used to assess your anaerobic abilities:
Glycolytic Power or VLamax Test
This is a test of the maximal rate at which energy is produced through the glycolytic system (i.e. excluding the CP system). However, it’s strongly related to overall anaerobic power.
As we learnt above, the glycolytic system produces pyruvate, which, in the absence of sufficient oxygen/mitochondrial capacity, is rapidly converted into lactate. Lactate is relatively easy to measure in the blood, via a simple fingertip or ear lobe blood sample. This means that, if we can measure the rate of lactate production, we can get a good idea of the rate of energy production via the glycolytic system.
The maximal rate of lactate accumulation (also referred to as Glycolytic Power or VLamax) can be approximated by completing an all-out effort that’s short enough to have a minimal contribution from the aerobic energy system (approximately 20-30 seconds works well). Lactate samples are taken before and after the effort (with several being taken post-effort to capture the highest lactate level in the blood, as levels will continue to rise after the effort stops, as lactate disperses from the muscles into the blood stream). The difference in pre- and post- lactate levels divided by the length of the effort performed gives you a VLamax value.
It’s worth noting that, as lactate sampling must be taken at discrete intervals, VLamax cannot be measured exactly. As the lactate sample is also taken usually at the finger or earlobe, this is relatively distant from the site of production (i.e. leg muscles), and any resulting measures will also be influenced by factors such as lactate transport/shuttling ability, and total blood volume. Thus, any measure of VLamax will only ever be approximate, and in our view can only ever be used to gain a high-level view of whether glycolytic power is high, medium or low.
Wingate Test
The Wingate Test is a classic test for anaerobic capabilities. It involves performing a 30s effort, beginning with a maximal sprint, and then attempting to sustain power as high as possible for the remaining effort.
The Wingate test is useful as it gives several markers of anaerobic capabilities. First, peak power sustained over the first 5 seconds gives a measure of the anaerobic power. The total work done throughout the whole of the 30-second effort gives an indication of anaerobic capacity, and the drop-off in power between the beginning and the end of the test gives an indication of anaerobic stamina.
A disadvantage of this test is that the anaerobic capacity might not be fully depleted by a 30-second effort, and therefore the test might underestimate this parameter. Secondly, the power produced during the test is dependent not only on the glycolytic system, but also the CP system, and it’s not possible to disentangle the contributions from these two systems.
Critical Power Test
A final test for anaerobic capabilities is the critical power test.
The basic premise of this test is that power output above a certain ‘critical power’ follows a hyperbolic power-duration curve as shown below.
The curve can be defined by two parameters: the critical power (CP) and W’ (pronounced as ‘W prime’).
CP is the power output that you’ll fall towards when riding at a high intensity as exercise duration is increased ‘indefinitely’ (‘indefinitely’ is a mathematical construct, and not actually true in practice, which is why this power-duration model fails to hold at or below CP). In practice, people can typically only sustain power outputs at CP for around 30-minutes (Vanhatalo et al., 2011). CP occurs at around the maximal lactate steady state (Poole et al., 2016).
W’ (measured in kJ – i.e. units of energy) is the amount of work that can be done above the CP, and is a marker of anaerobic capacity.
By performing a series of maximal tests (we recommend doing 3-4 maximal efforts, each lasting between 3-20 minutes), it is possible to determine CP and W’ from the power-duration relationship. The maths behind these calculations are beyond the scope of this article, but you can read more about critical power and download our critical power calculator here.
Balancing the Systems
Having understood how the anaerobic systems can be measured leads next to the question of how big you want these systems to be. Again, we will focus on the glycolytic system here, as this is the most trainable system and also makes the biggest contribution to anaerobic energy production.
When it comes to the glycolytic power, bigger is definitely not always better.
That’s because of the relationship between the anaerobic and the aerobic systems. With a higher glycolytic power, comes a greater rate of pyruvate/lactate production, which you’ll recall also means a higher rate of production of fatiguing metabolites. This can be true even at powers below the maximum anaerobic power, because an improved ability to produce power via glycolysis is associated with a decreased ability to use fats for fuel.
This is a problem for many cycling disciplines, because it means that for a given aerobic capacity, if we increase the glycolytic power (in order to improve anaerobic power and/or capacity), the rate of lactate production will likely exceed the rate of lactate clearance at a lower power output. Or in other words the lactate threshold goes down. This means the proportion of your aerobic capacity that you are able to utilise for an extended duration decreases. You can think of the lactate threshold as the gateway to accessing your aerobic potential or your ‘fractional utilisation’ (to read more on this, see here).
You’ll notice in the paragraph above we qualified that the above was true ‘for a given aerobic capacity’. That’s because the lactate threshold depends not only on the rate of lactate production, but also on the rate of clearance.
If you refer back to the first diagram of this article, you’ll be reminded that the main and most preferable way to clear lactate (or pyruvate) is via the aerobic energy system. So, we can effectively counteract the negative effects on lactate threshold power of having a high glycolytic power by also having a big aerobic capacity, allowing more effective clearance of lactate/pyruvate.
In other words, the appropriate size of the glycolytic power depends, in part, on the size of the aerobic capacity. The balance between these two capacities will dictate your lactate threshold*.
What about anaerobic stamina? Unlike the glycolytic power, there’s no direct negative consequence or compromise to having a higher anaerobic stamina. However, training to improve the anaerobic stamina will also result in some training of the glycolytic power, and therefore this type of training should still be used sparingly if the main priority is a high lactate threshold.
Discipline-Specific Considerations
As well as considering the size of the aerobic system when deciding how big the glycolytic power should be, we also need to consider the demands of the target cycling discipline. In particular, we need to decide how important the lactate threshold is (i.e. your ability to sustain a relatively high power over an extended period), relative to the glycolytic power (i.e. your ability to produce high power over shorter durations of seconds several minutes).
A hill climb specialist, for example, would require both a high glycolytic power in order to produce a high amount of power over a short duration and also a high anaerobic stamina, meaning anaerobic efforts can be sustained for longer. As this type of event is typically over very quickly, the lactate threshold isn’t too important. Training for hill climbs would therefore prioritise work on glycolytic power and anaerobic stamina.
At the other end of the spectrum are disciplines lasting around an hour or more, that require more of a steady-state effort (e.g. 25-mile time trials, sportives, the bike leg in a non-drafting triathlon). Here, high bursts of power are not as important. In this example, the lactate threshold should therefore be very high, meaning the glycolytic power would be much smaller.
Training for long, steady-state events would aim to raise the lactate threshold as close to the aerobic capacity as achievable. Little to no anaerobic training would typically be included.
Most other disciplines fall somewhere in the middle of these two examples, requiring a high power that can be sustained throughout a race, but also requiring a reasonable anaerobic power production to be able to respond to events in the race such as breakaways, accelerating out of corners, start and finish-line sprints etc. In these examples, the lactate threshold usually wants to be relatively high, but still leaving a bit of room for a reasonable glycolytic power. Training for these disciplines would usually involve spending the majority of time working on the aerobic capacity and lactate threshold, and potentially building in some anaerobic power training within a few weeks of key races, depending on the achieved balance between the aerobic and anaerobic systems. This process is often called “fine-tuning”.
In any case, it’s worth noting that for almost all disciplines, having a high aerobic capacity is beneficial. This is because it allows a greater proportion of energy to be produced aerobically (i.e. with no accumulation fatiguing metabolites) and because it allow a higher rate of pyruvate/lactate clearance, allowing a high anaerobic power production to be tolerated for longer. Aerobic capacity development would therefore be a component of training for all the disciplines described above.
Anaerobic Workouts
Having understood the extent to which we might want to use anaerobic training within a plan, here’s a selection of effective anaerobic workouts. We would typically structure training to first build anaerobic power, and then to improve stamina.
Anaerobic Power Workout
This session is designed to increase anaerobic/glycolytic power and capacity. The goal of the workout is to perform each interval at the maximum power that can be sustained for the 30-second duration. The recovery between intervals should be at least 5 times the length of the intervals themselves, to allow full recovery and maximum power generation.
This session can be adapted for different interval lengths, ranging from 20-seconds, up to around 60-seconds. You can also increase or decrease the number of intervals depending on fitness levels.
Anaerobic Stamina Workout
This workout aims to build anaerobic stamina more so than anaerobic power. As a result, the intervals are not quite a maximal effort, but still above VO2max intensity, with longer intervals and/or shorter recoveries. This workout really targets the ability to sustain anaerobic efforts for an extended period, or in repeated bouts.
This session can be adapted for a variety of interval lengths, ranging from 30-seconds to 2-minutes. In each case, the recovery interval should be less than 3 times the interval length. You can start out, for example with a 1:3 work-recovery interval, and then make the sessions more challenging by progressing towards a 1:1 work-recovery interval.
There is considerable variation in the power that can be produced anaerobically, so these intervals are best done ‘self-paced’ initially, to see what kind of power can be held consistently across the set of intervals. This will typically be in the range of 125-150% FTP depending on the interval duration. However, it might be necessary to increase or decrease this target depending on your anaerobic abilities.
Additional Considerations
One final thing to consider is when and how often to perform this type of training. In order to be able to hit the high power targets of these sessions, they need to be performed fresh, so are best scheduled after a recovery day (which would ideally include a short, easy ride, so the legs don’t get ‘sleepy’). These sessions are very stressful on the body, so should not be performed more than 1-2 times per week in most cases. As the intervals are fuelled almost entirely by carbohydrates, you should also make sure you are well fuelled for these sessions, having had a good carbohydrate intake in the 24-hours leading up to the sessions.
To conclude, it is worth reiterating that, for a given aerobic capacity, an increase in anaerobic power (or more specifically glycolytic power) will usually result in a reduction in the lactate threshold. So, any anaerobic training should be undertaken with caution, and for most athletes, only a small amount of this type of training will be beneficial, with excessive anaerobic training having a detrimental effect on overall performance. The body responds much faster to anaerobic training than to aerobic training, and good improvements can often be seen in 2-4 weeks.
* There are other factors that also impact the lactate threshold, such as lactate shuttling and buffering capabilities, but these are beyond the scope of this article.
References
Bangsbo, J., Mohr, M., Poulsen, A., Perez-Gomez, J., & Krustrup, P. (2006). Training and testing the elite athlete. J Exerc Sci Fit, 4(1), 1-14.
Francis, J. T., Quinn, T. J., Amann, M., & LaRoche, D. P. (2010). Defining intensity domains from the end power of a 3-min all-out cycling test. Medicine & Science in Sports & Exercise, 42(9), 1769-1775.
Poole, D. C., Burnley, M., Vanhatalo, A., Rossiter, H. B., & Jones, A. M. (2016). Critical power: an important fatigue threshold in exercise physiology. Medicine and science in sports and exercise, 48(11), 2320.
Vanhatalo, A., Jones, A. M., & Burnley, M. (2011). Application of critical power in sport. International journal of sports physiology and performance, 6(1), 128-136.
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