How Much of Running Is Grit and How Much Is Fitness?

Running, whether you're training for a 5K or a marathon, is as much a test of the mind as it is of the body. The question of how much success in running depends on psychological grit versus pure physical fitness has intrigued me for some time. 

So while cardiovascular endurance, muscular strength, and VO2 max are direct predictors of running performance, mental toughness plays an equally important role in training consistency, pain tolerance, and race-day performance.

Grit in Sport

Grit, as defined by psychologist Angela Duckworth in her famous book ’Grit: The Power of Passion and Perseverance’, refers to "perseverance and passion for long-term goals" (Duckworth et al., 2007). In the context of running, this can mean sticking to a training plan in bad weather, pushing through fatigue, or coming back stronger after injury or setbacks.

A growing body of research has examined the role of grit in athletic performance. For instance, Larkin et al. (2016) found that elite athletes scored significantly higher in grit compared to non-elite athletes, implying that perseverance may distinguish those who reach the top from those who don’t.

Additionally, studies by Martin and Gill (2018) indicate that athletes with higher grit are better able to maintain training volume and intensity across a season, which indirectly improves physical performance.

Physiology of Running Performance

Of course, grit alone doesn’t carry runners across the finish line. 

Aerobic capacity (VO2 max), lactate threshold, and running economy are primary physiological indicators of endurance performance (Joyner & Coyle, 2008). These elements are gradually developed through structured training over time, such as your tempo runs, long-distance sessions, and strength work.

According to a meta-analysis by Casado and colleagues (2020), runners who optimised these physiological metrics saw the greatest improvements in race performance, especially in events beyond 5km. This implies that physical training is a necessary condition for success. However, it’s not always sufficient.

Where Grit Fills the Gaps

Running inevitably involves discomfort, whether in the form of muscle fatigue, harsh weather, or mental boredom. This is invaluable as it can teach you how to deal with discomfort in other areas of life.

This discomfort is where grit steps in. Research by Slimani et al. (2017) found that mental toughness traits, including self-belief and emotional control, significantly correlated with endurance performance across multiple sports. In other words, if you took two athletes with similar fitness levels, they may perform very differently based on their psychological resilience.

Further, grit appears to play a vital role during moments when physical performance plateaus. A study by Tedesqui and Young (2017) suggests that athletes with high grit scores were more likely to persevere through periods of stagnation and injury, helping to maintain long-term commitment to their sport.

When Does Fitness Take a Backseat?

A popular saying among marathoners is that "the race begins at 32 kilometres" (or 20 miles), a point often referred to as "the wall." Physiologically, this is when your glycogen stores become depleted, and the body begins to rely more on fat oxidation, a slower and less efficient energy source. As a result, runners often experience extreme fatigue, decreased coordination, and mental fog.

While fitness undoubtedly influences how you reach this point, it’s grit and psychological endurance that often determine how you finish.

Research by Brick et al. (2016) explored cognitive strategies used during endurance performance and found that attentional focus (e.g., positive self-talk, goal setting) was significantly correlated with late-stage performance. Similarly, studies by Buman et al. (2008) suggest that psychological resilience plays a critical role during the final stretch of a marathon, as runners experience peak physical and mental fatigue.

Read more on self-talk in our article on resilience.

However, it's important to clarify that fitness never becomes truly irrelevant, it’s always sets up your foundations. Instead, what shifts is your limiting factor. Up to 30-32 km, physical conditioning is likely to be the most significant determinant of pace and comfort. Beyond that point, the marginal gains from fitness decrease, and psychological toughness becomes increasingly important (Stellingwerff, 2012).

Grit = Essential for Ultramarathons

In ultramarathon settings, this effect is even more pronounced due to the extreme physical and mental demands placed on the body. Knechtle et al. (2015) found that psychological traits such as resilience, stress tolerance, and intrinsic motivation were stronger predictors of ultra-distance performance as opposed to VO2 max once distances exceeded 50 km. 

This shift is partly because, beyond a certain point, nearly all runners are physically depleted so the differences in VO2 max or running economy offer diminishing returns. Instead, the ability to manage pain, control emotions, and stay mentally engaged with the task becomes the differentiating factor. 

Additional research supports this psychological tipping point. Both Brace et al. (2020) and Niering et al. (2024) reported that successful ultra-distance athletes and elite 100-mile runners consistently exhibited high self-efficacy, emotional intelligence, and mental toughness, traits that better distinguished finishers than physiological measures alone. These findings collectively suggest that in the ultra-endurance realm, psychological strength becomes the deciding factor once a baseline of fitness is met.

A Balanced Perspective

So, how much of running is grit, and how much is fitness? The answer isn’t binary. Fitness builds the foundation, enabling runners to develop speed, stamina, and strength. Grit ensures they stay the course, adapt to challenges, and maximise their physical potential.

If we were to venture a general framework, early stages of running may rely more heavily on developing fitness, while long-term and further distances success increasingly depends on grit to sustain effort and progress. As one study put it, "grit may not replace talent or training, but it may allow individuals to better use both" (Duckworth et al., 2007).

Conclusion

Running success is forged through a combination of physical preparation and mental resilience. While physiological capacity provides the raw capability to run far and fast, grit keeps you lacing up your shoes day after day. For amateur athletes balancing training with jobs, families, and life’s unpredictability, understanding and cultivating both grit and fitness is the key to long-term enjoyment and success in the sport.

References

1. Brick, N. E., MacIntyre, T. E., & Campbell, M. J. (2016). Attentional focus in endurance activity: New paradigms and future directions. International Review of Sport and Exercise Psychology, 9(3), 270–292. https://doi.org/10.1080/1750984X.2016.1148619

2. Buman, M. P., Omli, J. W., Giacobbi Jr., P. R., & Brewer, B. W. (2008). Experiences and coping responses of "hitting the wall" for recreational marathon runners. Journal of Applied Sport Psychology, 20(3), 282–300. https://doi.org/10.1080/10413200802078267

3. Casado, A., Hanley, B., Santos-Concejero, J., & Ruiz-Perez, L. M. (2020). World-class long-distance running performances are best predicted by volume of easy runs and deliberate practice of short-interval and tempo runs. Journal of Strength and Conditioning Research, 34(6), 1458–1465. https://doi.org/10.1519/JSC.0000000000003563

4. Duckworth, A. L., Peterson, C., Matthews, M. D., & Kelly, D. R. (2007). Grit: Perseverance and passion for long-term goals. Journal of Personality and Social Psychology, 92(6), 1087–1101. https://doi.org/10.1037/0022-3514.92.6.1087

5. Joyner, M. J., & Coyle, E. F. (2008). Endurance exercise performance: The physiology of champions. Journal of Physiology, 586(1), 35–44. https://doi.org/10.1113/jphysiol.2007.143834

6. Knechtle, B., Knechtle, P., Rosemann, T., & Lepers, R. (2015). Psychological aspects of ultramarathon running: Mood state, cognitive strategies and mental training. Sports Medicine and Arthroscopy Review, 23(2), 93–100. https://doi.org/10.1097/JSA.0000000000000066

7. Larkin, P., O'Connor, D., & Williams, A. M. (2016). Does grit influence sport-specific engagement and perceptual-cognitive expertise in elite athletes? Journal of Sports Sciences, 34(8), 754–764. https://doi.org/10.1080/02640414.2015.1075057

8. Martin, A. J., & Gill, N. D. (2018). Grit and engagement in sport: A study of New Zealand high school athletes. Journal of Applied Sport Psychology, 30(3), 298–311. https://doi.org/10.1080/10413200.2018.1444267

9. Slimani, M., Taylor, L., Baker, J. S., & Chamari, K. (2017). Effect of mental training on performance and psychological parameters in sports: A systematic review. Trends in Sports Sciences, 24(1), 1–10.

10. Stellingwerff, T. (2012). Case study: Nutrition and training periodization in three elite marathon runners. International Journal of Sport Nutrition and Exercise Metabolism, 22(5), 392–400. https://doi.org/10.1123/ijsnem.22.5.392

11. Tedesqui, R. A. B., & Young, B. W. (2017). Investigating grit variables and their relations with sport expertise development. Journal of Expertise, 1(1), 18–30.