Fatigue Resistance & ‘Durability’ in Cycling: Tests and Training Tips
More often than not, the winning moves in a cycling competitions are made in the closing stages of an event. The ability to keep producing high power outputs after several hours of riding is a key cycling ability, commonly referred to as ‘endurance’, ‘fatigue resistance’ or ‘durability’.
Most common cycling tests are performed in a ‘fresh’ state, or in other words, with minimal pre-existing fatigue. These tests tell us little about an athlete’s ability to resist fatigue and perform well after prior work during tough races and challenges.
However, a recent study (Muriel et al., 2022) suggests that the ability to produce hard efforts in the latter stages of a race is a better differentiator between WorldTour and ProTeam cyclists than their fresh power numbers. This underlines the importance of being able to assess and train fatigue resistance as a specific ability.
In this article, we’ll look at some methods for testing fatigue resistance so that you can assess your abilities and gauge whether these are improving with training. We’ll also take a look at the factors that contribute to fatigue resistance, as well as the types of sessions are best for developing this ability.
Testing Fatigue Resistance
There are several ways to test your fatigue-resistance or ‘durability’.
Method 1: Fresh and Fatigued Max Efforts
One approach is to perform a ‘fresh’ maximal effort towards the beginning of a ride (after a 15-20 minute warm-up).
This is then followed by an hour or so riding at a steady wattage in order to build up fatigue.
A 'fatigued’ maximal effort is then performed to see how much your power has dropped between your fresh and fatigued efforts, and thereby quantify the impact of fatigue.
An example is shown below:
In our experience, a good level of fatigue resistance would see less than a 5-8% decline between fresh and fatigued power, although this of course depends on how long and intensively you ride between your fresh and fatigued efforts, as well as the length of the efforts themselves. For this reason, this test works best as personal comparator - i.e. allowing you to track changes over time - rather than a test that allows you to benchmark your abilities relative to other riders.
Method 2: Fresh and Fatigued RPE Efforts
Another approach if you’re not a fan of maximal effort testing is to perform your fresh and fatigued efforts according to your ‘rating or perceived exertion’ or ‘RPE'. In this case, you could, for example, aim to ride for 2-mins at a fixed RPE (e.g. 7/10) at the beginning of a ride, and then again at the end of a ride, without looking at power.
The drop in power between the two efforts is an indication of fatigue.
An example is shown below:
Testing tips
Make sure the wattage you’re riding at between ‘fresh’ and ‘fatigued’ efforts is relatively stable, so that you can replicate this easily in subsequent tests. If you find your power hard to control outdoors, then it might be helpful to perform this test indoors.
Try to make the testing race-specific. So if you tend to race shorter, races like XCO or short road races, then you might want to make the middle portion of your ride (i.e. the part between fresh and fatigued efforts) relatively short and high-intensity. The examples above, with 1-hour at 90% FTP between fresh and fatigued efforts would be a good protocol for these types of races. In contrast, if you’re training for a long event like a sportive or ultra-distance race, then you might want to make the middle portion lower intensity and longer (e.g. riding at 75% FTP for several hours or more).
Likewise, try to make the length of your fresh and fatigued efforts race-specific too. So if you are training for events that usually end in a bunch sprint, then make your fresh and fatigued efforts short and intense to reflect that. Whereas if you’re training for an event where you anticipate a long break-away effort or sustained finishing climb, for example, then make your fresh and fatigued efforts longer and lower intensity. The great thing about these test protocols is that you can tailor them to your specific race demands!
Try to keep your nutrition, hydration and any supplement/stimulant use (e.g. caffeine) consistent between tests, so that these factors don’t contribute to differences in performance across test days.
Likewise, try to test under similar environmental conditions, as things like heat, altitude and humidity can all impact your fatigue-resistance.
Factors contributing to fatigue resistance
The cause of fatigue in long events is multi-factorial and not yet fully understood. However, the main factors that appear to contribute to fatigue-resistance or durability are:
1. The ability to use fats for fuel
Broadly speaking, fats are a preferred source of fuel for the body at lower intensities. However, as riding intensity increases, we need to derive more energy from carbohydrates and less from fats, since carbohydrates provide a more rapid fuel source.
The body stores carbohydrates in the form of glycogen in the muscles and liver, and as glucose in the blood. However, the body is only capable of storing enough glycogen to fuel exercise for around 1.5H of all-out riding. It’s also very hard to replenish muscle glycogen during exercise, and falling glycogen levels is a key trigger for fatigue.
Therefore, having a higher capacity to use fats for fuel at a given wattage means that you can conserve more precious muscle glycogen to stave-off feelings of fatigue, and to save this important fuel source for key points in the race, when the intensity is high.
The ability to use fats for fuel is highly trainable. Untrained individuals can have such a poor capacity to use fats for fuel that even when at rest, they must derive significant amounts of energy from carbohydrates (e.g. nearly 50%) (Calonne et al., 2021).
On the other hand, highly trained athletes have the capacity to oxidise fats at ~4-5 times the rate of untrained individuals, and can still rely substantially on fat as a source of fuel event when riding at ~70-75% VO2max (Achten & Jeukendrup, 2003).
2. Resistance to muscular damage
Muscle damage in the form of tearing and swelling is typically less pronounced in cycling than in other forms of exercise that involve higher levels of impact and/or eccentric contractions (e.g. running). However, muscle damage does occur after extended periods of cycling, and this damage is also thought to contribute to fatigue.
In addition to this physical damage to the muscle fibres, over the course of a long ride the muscles themselves also begin to become more ‘dysfunctional’ and do not work as effectively. There are numerous reasons for this dysfunction. Examples include the leakage of molecules and other substances that play a role in muscle contraction, such as sodium and potassium. These processes can interfere with the ability of the muscles to contract, and also the ability of the mitochondria to produce energy aerobically (Abbiss & Laursen, 2005).
3. Resistance to central fatigue
With extended periods of riding, neural activation of the muscle fibres by the central nervous system also decreases. This is known as central fatigue.
Studies have been able to isolate the impact of central versus muscular (sometimes referred to as ‘peripheral’) fatigue. These studies have compared the force that a subject can produce through voluntary contraction with the force that can be generated from electrical stimulation of the muscle. The former represents a combination of central and muscular fatigue, whereas the latter represents muscular fatigue only, as the electrical stimulation replaces the central nervous system.
After a 40km time trial, voluntary contraction was found by Thomas et al. (2015) to be reduced by 16% and electrically stimulated force was reduced by 29%. Interestingly, the longer the activity, the more dominant central fatigue seems to become (Saugy et al., 2013; Thomas et al., 2015).
How to improve fatigue resistance
Just in the same way that we don’t fully understand all the factors that contribute to fatigue, we don’t currently fully understand how to develop fatigue resistance, particularly when it comes to improving resistance to central fatigue and muscle dysfunction. However, there are some key methods, backed up in research and in the field, and we’ve summarised these below.
1. Long endurance rides at a controlled ‘Zone 2’ intensity
These rides specifically target improvements in fat oxidation capacity, but probably also help with resistance to central fatigue and muscle damage.
They are performed at an intensity where fat oxidation rates are near maximum, which is often termed ‘Zone 2’ in a 6 or 7 zone system (for more on zones, see here).
To get the intensity of these rides right, you ideally want to make sure you’re riding close to, but just slightly below your so-called ‘aerobic threshold’.
Your aerobic threshold is the intensity at which you begin to derive increasing amounts of energy from carbohydrate rather than fat oxidation. Broadly-speaking, your aerobic threshold will generally sit somewhere around 65-85% FTP. However, this can vary a lot between people, and the best way to check that you’re riding at the right intensity is to pay attention to your breathing.
In a Zone 2 ride, you should find that your breathing rate always stays ‘conversational’. This means that you can speak full sentences comfortably, and aren’t needing to shorten your sentences or take breaths in unnatural places. If you were chatting to someone while riding at Zone 2, they would still be able to hear from your breathing that you are exercising, but you can happily string together multiple sentences without gasping for breath!
Many experts believe that, if you’re really looking to work on your fat oxidation ability, you need to take care to avoid efforts that take you above your threshold. A short acceleration lasting a few seconds is fine, but anything more can elevate levels of lactate in your blood and muscles for as much as 20-30 mins after each power surge. Since lactate suppresses fat oxidation, this is something we want to avoid as much as possible. Some of the best endurance athletes in the world are extremely strict with their intensity control in endurance rides, and it does seem to pay dividends if you have the self-discipline to stick to this regime.
It’s also quite important that these rides are long - or in other words challenge your current endurance abilities. So, for example, if you’re quite comfortable completing 2-hour rides, but find 3-hour rides a challenge, then your long endurance rides should probably be pitched around 2.5-hours, building up to 3-hours as your abilities develop.
The reason for this is that some of the most potent adaptations from your endurance rides occur in the latter stages, when your muscle fibres are beginning to fatigue and glycogen levels are lowered. At this point, some of the workload is passed over to higher-power muscle fibres (so-called Type IIa fibres), and these fibres are stimulated to become more aerobically efficient and better able to use fats for fuel. These special conditions of pre-existing fatigue and glycogen depletion are hard to bring about in shorter rides, and this illustrates the importance of making at least one of your weekly rides a bit longer than the ‘norm’.
2. Long endurance rides with ‘late-stage’ intensity
These rides can provide a bit of progression over the basic endurance ride as described above. With this session, the majority of ride time is spent in Zone 2 as described above. However, within the latter 30-60 minutes, you can build in some higher-intensity riding, which helps train both your mental and muscular ability to ride hard in the presence of existing fatigue.
A common sessions we like to use is a ‘negative split ride’, where the last 30-60 mins of the ride is performed at a Zone 3 intensity (between the aerobic threshold and FTP/critical power).
Another good session includes late-stage hill reps performed at or slightly above FTP.
3. Long endurance rides with pre-fatiguing intervals
Another format that we like to use is pre-fatiguing intervals.
With this session, you simply incorporate your usual interval session into the beginning of a longer endurance ride. This has the benefit that the intervals help to create a high level of fatigue and glycogen depletion, thereby creating those ‘special conditions’ described above that are particularly helpful for developing endurance.
The remainder of the ride is then performed at a steady Zone 2 intensity, as described above.
This session works best if you have at least 1-2 hours to ride after your intervals. This is because it will likely take at least 15 to 30-mins for your blood lactate levels to reduce after the intervals and to reach a state where those ‘special conditions’ are optimal for developing fat oxidation.
4. ‘Muscular Endurance’ Intervals
So-called ‘muscular endurance’ intervals are thought to help build resistance to muscular damage.
These efforts involve riding at a ‘Zone 3’ intensity (i.e. between the aerobic threshold and FTP/critical power), and are usually performed at a low cadence (~60-70rpm) in order to increase the force demands on the muscles.
Zone 3 intervals can be structured in a variety of formats, including shorter (e.g. 5-min) or longer (e.g. 15-20-min) blocks. The length of the recovery period doesn’t matter too much, so you can also include them in an unstructured way e.g. whenever you encounter a hill when riding outdoors.
5. Maximal Strength Training
Finally, working on improving maximal leg strength has been shown to help enhance endurance. The reason for this is not fully understood, However, one theory is that when riding at a given power output (say 60% FTP), increased muscle strength means that muscle fibres are being worked at a lower percentage of their maximal load, thus resulting in less muscular damage (Rønnestad, & Mujika, 2014).
Another theory is that the increased strength of Type I fibres means that fewer Type IIa fibres need to be recruited for a given output. As Type I fibres are more aerobically efficient, this may result in increased glycogen sparing, meaning more glycogen is available for hard efforts in the latter stages of riding/racing (Rønnestad, & Mujika, 2014).
The best way to develop muscular strength is to use heavy weights, aiming for between 3-5 sets of 4-8 reps per exercise, performed at a relatively slow speed, with 2-6 minutes of recovery between sets. We recommend focussing on exercises that closely mimic movement patterns on the bike. Squats and deadlifts are particularly good.
Of course, as with any strength training, it’s always wise to consult with a trained strength coach to ensure that you’re using good form when exercising to minimise the risk of injury.
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If you’d like more ideas for sessions to develop fatigue-resistance, as well as other key cycling abilities, we have a wide selection of workouts that can be easily imported directly into Zwift, Garmin etc. in our workout library. This library also includes progressions so that you can understand how to evolve your training as you adapt.
We hope you’ve found this article useful in understanding more about how you can test and train your fatigue-resistance. If you have any questions, please comment below!
Further Reading
For anyone looking to learn more about fatigue-resistance, there are two excellent articles by cycling coach Marco van Bon linked below:
References
Abbiss, C. R., & Laursen, P. B. (2005). Models to explain fatigue during prolonged endurance cycling. Sports medicine, 35(10), 865-898.
Achten, J., & Jeukendrup, A. E. (2003). Maximal fat oxidation during exercise in trained men. International journal of sports medicine, 24(08), 603-608.
Calonne, J., Fares, E. J., Montani, J. P., Schutz, Y., Dulloo, A., & Isacco, L. (2021). Dynamics of fat oxidation from sitting at rest to light exercise in inactive young humans. Metabolites, 11(6), 334.
Muriel, X., Mateo-March, M., Valenzuela, P. L., Zabala, M., Lucia, A., Pallares, J. G., & Barranco-Gil, D. (2022). Durability and repeatability of professional cyclists during a Grand Tour. European Journal of Sport Science, 22(12), 1797-1804.
Rønnestad, B. R., & Mujika, I. (2014). Optimizing strength training for running and cycling endurance performance: A review. Scandinavian journal of medicine & science in sports, 24(4), 603-612.
Saugy, J., Place, N., Millet, G. Y., Degache, F., Schena, F., & Millet, G. P. (2013). Alterations of neuromuscular function after the world's most challenging mountain ultra-marathon. PloS one, 8(6), e65596.
Thomas, K., Goodall, S., Stone, M., Howatson, G., Gibson, A. S. C., & Ansley, L. (2015). Central and peripheral fatigue in male cyclists after 4-, 20-, and 40-km time trials. Medicine & Science in Sports & Exercise, 47(3), 537-546.
