Four Ways to Improve Fatigue Resistance

by Laura Norris

October 16, 2024
10:38 am

Why do some runners slow down at a marathon more than others? Two marathoners could have nearly equal fitness (VO2max, lactate threshold, and running economy) and race performances at shorter distances. Yet one may slow down in the final stretch of the race, while the other holds onto pace. Why? The latter athlete has better fatigue resistance.

Fatigue resistance (often called “durability” or “physiological resilience” in the literature) is now being understood as the fourth variable in performance. Fatigue resistance can be defined as an athlete’s ability ot “resist deterioration of physiological characteristics” and is an “independent factor contributing to endurance performance” (Nuuttila et al., 2024).

The other three variables are VO2max, lactate threshold (MLSS), and running economy. Along with these factors, durability contributes to performance in the marathon and ultra-marathon distances. Low durability manifests as slowing down in long races (marathons and ultras). You may observe a decoupling of heart rate and pace late in races: heart rate increases while pace slows.

A 2023 analysis in Sports Medicine examined heart rate and pace data over 82,000 marathoners. Runners who experienced <10% decoupling over the final 8km of the race finished an average of 21 minutes faster than those who experienced >20% decoupling. Clearly, fatigue resistance matters when improving marathon performance.

By training how your nervous system responds to fatigue and by using strategies to maintain high carbohydrate availability during exercise, you can improve your durability. How do you do that? This article will guide you through simple yet effective approaches for improving your fatigue resistance – so that you can finish your marathon or ultra strong.

1. Optimize intra-race carbohydrate intake

A seminal 2023 review in Journal of Physiology provides numerous insights into understanding fatigue resistance. One approach for measuring durability is how stable one’s maximal oxidative metabolic steady state remains throughout prolonged exercise. If one’s MLSS can remain stable after running for several hours, they have higher fatigue resistance.

The researchers concluded that adequate carbohydrate availability contributes to maintaining MLSS after two hours of endurance exercise. Athletes who supplemented 60 grams of carbohydrate per hour experienced less fatigue and slowdown after two hours compared to placebo participants.

You may hear some running influencers tossing around numbers of 90 or even 120 grams of carbohydrates per hour. Research does support this high carbohydrate supplementation as a tactici for delaying fatigue in during ultra races (such as this 2021 review.)

However, in higher-intensity races such as the marathon, a carbohydrate intake that is too high may set marathoners up for a case of the runner’s trots. Marathoners should start with 60-75 grams of carbohydrate per hour and observe individual response – and then scale up if GI symptoms permit.

2. Strategically run on tired legs

In coaching practice, I have seen runners benefit from long runs of 21-22 miles – if they are an experienced marathoner. Even one run of 21-22 miles before the race can trigger favorable adaptions for durability.

There is a fine line between improving durability and overreaching in training. With some of these practices, more is not better. For example, running 12 miles the day after a long run will not spur greater adaptations than 6-8 miles. Likewise, multiple 22-mile runs will not further improve your performance. Implement these training practices deliberately and back off at the first sign of injury or overtraining.

A medium-length easy run the day after long runs (i.e. 6-8 miles the day after 12+ miles)
Lengthen cooldowns after hard workouts to 1-3 miles total
Run long runs over a hilly route
A long run of 21-22 miles
Back-to-back long runs for ultras

3. Include progressively paced workouts in training

A more advanced approach to running on tired legs while running at goal pace. The higher intensity burns more glycogen, when your body has already utilized a large amount of glycogen. Metabolically, these workouts train your body to store more glycogen. Additionally, these workouts present neuromuscular stress (maintaining higher rates of contraction) that may reduce fatigue later in the race.

This approach should be applied strategically. Not every goal pace workout should be done on tired legs, nor should every long run finish at goal pace.

Emphatically, these are not the only workouts you include in training to improve fatigue resistance. A 2023 study demonstrated that both low-intensity and high-intensity training improved durability in recreationally active adults.

These progressive workouts should be part of the many types of workouts you do in a training cycle. Additionally, you want to follow the principle of specificity: do these workouts in the 6-10 weeks prior to a goal race. These workouts are not intended for early season!

Sample progressive workouts:

16-20 miles with final 4 miles at marathon pace
20 minutes at marathon pace/12 minutes at half marathon pace/6 minutes at 10K pace (3-4 min jog after each)
2 miles at MP/3 min jog/4 x half-mile at HMP (1.5-min jog)/3 min jog/2 miles at MP

4. Train with long goal pace workouts

Similar to progressive workouts, long tempos place a higher demand on your metabolic and neuromuscular systems. These workouts also prepare you for the ability to focus on the task of pacing, even as central fatigue sets in.

Reserve these workouts for the specific weeks of your race training. These long tempos are best programmed in the 3-8 weeks before your race, when you are fit enough to handle them. Avoid doing these during your taper, since they do have a higher recovery demand.

As with the progressive workouts, these workouts have a high recovery demand. Do not do them weekly in training. Instead, deliberately program two to three sessions throughout your marathon build.

Sample long tempo workouts:

6-10 miles at goal marathon pace
A 15-17 mile long run, with 8-10 miles continuous at goal pace*
10-15 miles at 50K to 100K pace

*This is my favorite workout to program two weeks out from a marathon!

Related: The How and Why of a Tempo Run

Combat Fatigue Resistance

You can improve your marathon performance and stop slowing down in the final miles of the race. The science of fatigue resistance is still growing, so these recommendations may change wiht time. For now, you can use the evidence-based approach of high-carbohydrate fueling and the practice-proven approach of training to resist fatigue.

Importantly, training fatigue resistance does not supersede the other three physiological variables. You cannot expect to perform optimally at a marathon if you only train to improve durability. Rather, you want to develop a training plan and race strategy that address all four variables.

Finally, these are tips for experienced marathoners. If you are training for your first marathon, the following practices may be too aggressive and could increase your risk of injury.

Consume 60-90 grams of carbohydrate per hour
Incorporate fast finish or cutdown pace workouts in training
Include easy running done on tired legs in training
Include a couple of long tempo runs throughout your build

Want more guidance on improving your marathon performance?

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