82. HOW TO TRAIN DURABILITY?

Photo by Stefan Scheepmaker on Unsplash

In the previous KisW Research Notes we saw some studies on the durability topic.

Here is a summary:

• Definition of Durability

  The ability to decrease as less as possible physiological parameters and performance during prolonged exercise (at least ~3 hours). It can be named also ‘fatigue resistance’ or ‘fatigue resilience’.

• Physiological Mechanisms Determining Durability:

  Durability doesn’t seem to be related to traditional physiological endurance marker like VO2max and threshold’s power output. In other words, having a higher VO2max or FTP doesn’t necessarily mean to have a higher durability. So, we can consider this capacity as an additional independent parameter determining endurance performance. (1) On the other hand, one of the physiological determinant of durability is preserving carbs availability and glycogen levels during prolonged exercise. (2) However, a recent study reported that, in continental level cyclists. when large amounts of carbs are ingested during exercise (100 g/h, a scenario similar to nowadays cycling races) fat oxidation levels during exercise were not related to durability. (3) This can suggest as glycogen depletion and so fat oxidation capacity is only one of the possible physiological determinant of durability and the higher and higher intake of carbs during race are moving the place of durability, at least in part, elsewhere. Where? We don’t know yet but it is likely that it can be:

  • muscle /soft tissues damage: even if it is less compared to other sports with more eccentric contractions like running, some level of muscle damage has been reported even during prolonged cycling;

  • general body inflammation;

  • central fatigue: central nervous system fatigue (brain and spinal cord) that leads to the inability to proper recruit muscles to produce watts;

• How durability can be tested?

  There are 3 ways:

  1. Standardized test (gold standard), that is performing a specific test in a fresh state and then repeat it after a ‘fatiguing’ protocol. When using this method, the durability score is the % decrease in the performance marker between fresh and fatigued state.

  2. Record Power Outputs after a certain energy expenditure (kilojoules) However, we should consider that just using a kilojoules benchmark (e.g. 3000kjs) can be misleading as the performance decrease during prolonged exercise depends also on the intensity and duration of the ride and not only on the energy expenditure.

  3. Power-Heart Rate Decoupling

  Higher the heart rate drift during the second ride to produce a certain power output, lower the durability. Lower the heart rate drift during the second part of the ride to produce a certain power output, superior the durability.

  To learn more about these testing methods you can refer here.

So, on the durability topic we have the definition, some physiological underpinnings and testing methods. What about the best training strategies to improve durability?

How durability might be trained?

A review by Professor Andrew Jones (the scientific director of Eliud Kipchoge’s ‘Breaking Two’ historical marathon record sponsored by Nike) and Brett Kirby (University of Exeter, UK) published in 2025 on Scandinavian Journal of Medicine & Science in Sports tried to answer this question.

Please, note that this is a preliminary work as durability is a relatively new topic in sport science. So, as the original title of the review indicates (Physiological Resilience: What Is It and How Might It Be Trained?), the training strategies outlined are ‘just’ hypothesis supported by some preliminary data (but still quite interesting), while more studies in the future will help us to understand more on the topic.

Have a good read of our summary!

Image from Jones and Kirby 2025. (4)

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1. DURABILITY IS A TRAINABLE CHARACTERISTIC

First: durability is a trainable characteristics and not only a genetic trait. This is the starting point, so that we are sure that it makes sense to speak about training strategies to improve durability. This information rises from the fact that trained people have superior durability compared to untrained people. For example, in 2024 Unhjem (Nord University, Bodø, Norway) reported that, after 1h of running in zone 3 (in a 5/7 zones model), ‘active’ adults increased more oxygen cost and reduce more VO2max when compared to endurance trained runners. So, given that durability is trainable, we can proceed to see how it might be trained.

2. FOR THE NEWBIERS: SIMPLY DOING ANY TIPE OF ENDURANCE TRAINING IMPROVES DURABILITY

It is the same as for improving VO2max/Thresholds/FTP/critical power. If you are not already (well) trained, everything you will do at the beginning will improve your durability regardless of the details of the training performed (high volume vs high intensity or short high intensity intervals vs long high intensity intervals, etc. …). For example, a study published by the Finnish group led by Matomäki and Colleagues (University of Jyväskylä) reported a similar improvement in durability after 4 weeks of extensive low‐intensity training vs much lower volume high‐intensity training in sedentary/recreationally active participants. (5)

3. BEST TRAINING STRATEGIES TO IMPROVE DURABILITY

While for the newbiers everything works, here some more suggestions from data and anectodal evidence from world-class athletes that can help to boost durability in already trained endurance athletes.

3.1 A High Training Volume at Low Intensity

Doing/Maintaining a relatively high volume spent at low intensity seems to be important to optimize durability. In this scenario, low intensity is defined as below the first lactate/ventilatory threshold, so zone 1/2 in a 5/7 zones model.

Specifically, Spragg and Colleagues (Tudor Pro Cycling Team) reported that the fluctuation over a season of some record power outputs after 2000 kjs (but not the record power outputs in the fresh state) of continental level cyclists was related to the amount of the low intensity volume performed. Higher the low intensity volume performed, better record power outputs after 2000 kjs were observed.

In addition, in a study we commented on a previous KisW Research Note (read more here) we saw that adding high intensity 3 times per week for 2 months after general the general preparation period improves performance in a fresh state both when maintaining the overall volume and even when dropping it by 35%. However, performance in a fatigued state (after hour of exercise), and so durability improved only in the group which maintained the overall training volume. This can further highlight the importance of accumulating a High Training Volume at Low Intensity to boost durability.

3.2 ‘Very Long’ Rides

In a recent (2025) still unpublished PhD thesis by Michele Zanini, it is highlighted that in a group of trained runners with similar V̇O2max and 10km performance:

“Those that regularly practiced long runs of greater than 90min were better able to preserve running economy compared to those that were less accustomed to long runs (3.1 vs. 6.0% increase in Oxygen cost) over a 90min run at ~80% V̇O2max.” (4).

Of course cycling and running are different sports, and 90 minutes can’t be really considered a long ride for trained cyclists. In fact, 1 hour of running is much more demanding than a 1 hour of cycling, both from a metabolic (more energy expenditure) and a biomechanical (more impact forces). So, what is a very long ride in cycling? I think it depends on what is the habitual very long ride at individual level. If you rode max just 2 hours in the past, a 3 hours ride can already considered ‘a very long ride’. On the other hand, for a professional cyclist who trains 3/4 hours per day on average, a very long ride can be considered a 6 or even a 7 hrs (!) ride.

3.3 High Intensity Efforts in the Second Part of Long Rides

Another strategy that has not been already studied but which might improve durability is performing high intensity efforts in the second part of long rides. Intuitively, this makes sense: performing a hard effort in a fatigued state is a very specific stimulus for durability.

This strategy has already been performed by some world class endurance athletes. For example, it was reported that a Giro d’Italia Final General Classification Podium finisher, in the 5 months preparation leading to this achievement, he performed almost all the medium and high intensity work (from zone 3 onwards in a 5/7 zones model) in sessions longer than 3-4 hours. (7)

Furthermore it is also anecdotally reported as world-class kenyan runners usually perform their long runs progressively increasing the intensity within the workout.

“A key session for Kipchoge and his training partners is the long run, often of 40 km, which is performed over hilly and rough terrain and at high altitude (2000–2400 m). Interestingly, this session is rarely performed at a consistent, “steady” pace, but rather starts at an easy pace as the athletes warm up and becomes progressively more intense as the session continues (e.g., starting at ~10 km/h and finishing at ~20 km/h). In this way, the athletes work “through the gears” and are running faster as they become more fatigued.”

- Jones and Kirby 2025 (4) -

Future studies could investigate whether this is actually an effective strategy to improve durability.

3.4 Heavy Gym Strength Training

There is some evidence that different forms of resistance training improve durability. For example, Ronnestad et al. (8) reported that elite cyclists performing heavy gym strength training twice per week for 12 weeks improved their durability, while this was not the case of the control group which performed only on the bike endurance training (read more here). In line with this, again in the recent (2025) still unpublished PhD thesis by Michele Zanini, “compared to a control group of well-trained runners who persisted with only endurance training, heavy strength and plyometric training for 10 weeks resulted in a less pronounced increase in oxygen cost during a 90min run and a substantially improved time to exhaustion during a subsequent test at 95% V̇O2max”. (4)

Why strength training improves durability? When performing low intensity prolonged exercise (cycling/running), the type I (more resistant to fatigue) muscle fibres are recruited early and then, after they become fatigued, type IIa (less resistant to fatigue) fibres are recruited. As strength training increases peak force, it could be that, after hitting the gym for some weeks, type I fibres contract at lower % of maximum force to generate a given power output on the bike in the initial phases of prolonged rides. Consequently they get tired later, postponing the recruitment of type II fibres and so increasing durability/fatigue resistance. However this is just a speculation, without data to support it.

3.5 Fasted/Low Carbs Easy Sessions

Another possible solution to increase durability is performing some easy intensity ride (zone 1/2, max z3 in a 5/7 zones model) in a fasted or low carbs state in order to stimulate maximally the fat metabolism and increase the ability to use fat as fuel and so durability. Why? We saw that durability is linked (in part) to preserve muscle glycogen levels and carbohydrates availability. Even in very lean individuals, fats are a virtually unlimited energy store while carbs are not.

Energy stored in the body as carbs and fats for a 70kg person with a 10% of far mass. Data from Maunder et al. (8)

So, being capable to use as much as possible fats (the unlimited resource) during exercise could make spare carbohydrates/glycogen (the limited resource), and increase durability. Doing low intensity rides in a fasted/low carbs state (with little or no carbs both before and during the ride) permits to train at fatmax, that is the intensity at which you have the maximum rate of fat oxidation. In fact, fatmax occurs approximately in zone 2 in a 5/7 zones model (anecdotally can be even low zone 3 in some pro cyclists) and carbs’ ingestion lowers fat oxidation levels probably through an increase in blood insulin levels. It is important to acknowledge that, while this approach seems intuitively reasonable and widely used on the field, no study has yet demonstrated tat training at fatmax increase the ability to use fat as fuel and so durability. It is just a speculation based on physiological mechanisms. Please, note that the fasted/low carbs training approach can work only for few specific sessions, while it is unpractical on longer periods and if the overall load is high and you are performing a relevant amount of high intensity training. In this case, a low carb approach will lead just to fatigue, non-functional overreaching and impossibility to complete the training program.

BRIEF SUMMARY:

• Durability is trainable

• For the newbiers, every kind of endurance training improves durability

• Already (well) trained endurance athletes that would like to improve durability should try one or more of these training strategies:

  1. Increase training volume at low intensity

  2. Perform some very long rides

  3. Put high-intensity efforts in the second half of long rides

  4. Heavy gym strength training

  5. Some fasted/low carbs easy sessions.

When new studies about effective training strategies to improve durability will be published, we will share team with Knowledgeiswatt Community!

Thanks for Reading! Share with your Team!

Do you have a question? Ask in the comments section!

Gabriele Gallo, PhD in Exercise and Sport Sciences

Founder of Knowledgeiswatt

REFERENCES:

1. Valenzuela PL, Alejo LB, Ozcoidi LM, Lucia A, Santalla A, Barranco-Gil D. Durability in Professional Cyclists: A Field Study. Int J Sports Physiol Perform. 2022 Dec 15;18(1):99-103.

2. Clark IE, Vanhatalo A, Thompson C, Joseph C, Black MI, Blackwell JR, Wylie LJ, Tan R, Bailey SJ, Wilkins BW, Kirby BS, Jones AM. Dynamics of the power-duration relationship during prolonged endurance exercise and influence of carbohydrate ingestion. J Appl Physiol (1985). 2019 Sep 1;127(3):726-736.

3. Ørtenblad N, Zachariassen M, Nielsen J, Gejl KD. Substrate utilization and durability during prolonged intermittent exercise in elite road cyclists. Eur J Appl Physiol. 2024 Jul;124(7):2193-2205. doi: 10.1007/s00421-024-05437-y. Epub 2024 Mar 5. Erratum in: Eur J Appl Physiol. 2024 Jul;124(7):2207-2208.

4. Jones AM, Kirby BS. Physiological Resilience: What Is It and How Might It Be Trained? Scand J Med Sci Sports. 2025 Mar;35(3):e70032.

5. Matomäki P., Heinonen O. J., Nummela A., et al., “Durability Is Improved by Both Low and High Intensity Endurance Training,” Frontiers in Physiology 14, no. 2 (2023): 1128111, 10.3389/fphys.2023.1128111.

6. Spragg J., Leo P., and Swart J., “The Relationship Between Training Characteristics and Durability in Professional Cyclists Across a Competitive Season,” European Journal of Sport Science 23, no. 4 (2023): 489–498, 10.1080/17461391.2022.2049886.

7. Gallo G, Mateo-March M, Fuk A, Faelli E, Ruggeri P, Codella R, Filipas L. The Day-by-Day Periodization Strategies of a Giro d'Italia Podium Finisher. Int J Sports Physiol Perform. 2024 Feb 9;19(5):505-509.

8. Maunder E, Kilding AE, Plews DJ. Substrate Metabolism During Ironman Triathlon: Different Horses on the Same Courses. Sports Med. 2018 Oct;48(10):2219-2226.