In Episode 36 of The Trail Running Briefing, I take you through the ARC100 by UTMB from the perspective of someone who has raced it twice, in 2025 and 2026.

This episode is designed as a practical course guide for runners preparing for the race. I break down the key sections of the route, including the wet and boggy terrain around Lizard Point and Mullion, the runnable stretches towards Penzance, the technical section from Mousehole to Porthcurno, and the importance of using Land’s End as a chance to reset.

I also focus on what I consider the toughest part of the race: Pendeen to Lelant. This long, technical section can take many hours, so carrying enough water and nutrition and preparing mentally for slow progress is essential.

Along the way, I share lessons from my own experience, including foot management, accepting wet conditions, using barrier cream, training with wet feet, pacing the runnable sections sensibly, and which parts of the course are most worth recceing.

The key message is simple: don’t race the distance, race the terrain in front of you.

Cross-training can be a valuable tool for ultrarunners, but it should always serve a clear purpose.

In this episode of The Trail Running Briefing, I explore why specificity still matters, especially for mountain ultrarunners. A long ultra is not simply one discipline: it involves running uphill, running flats, running downhill and, very importantly, power-hiking steep climbs.

We look at why uphill walking can be one of the most race-specific forms of “cross-training”, how cycling can build additional aerobic volume with less impact, and where swimming can be useful during recovery, injury management or high-load periods.

I also explain why strength training should not really be considered cross-training at all, but rather an essential part of ultramarathon preparation.

The key question is not: “What is the best cross-training?”

It is:

“What adaptation am I trying to create, and what is the most specific way to achieve it without adding unnecessary fatigue?”

Train the engine but train the movement too.

Key references:

1. Endurance Coach GmbH et al. (2026). Cross-training between running and cycling: effects on VO₂max and running performance — a systematic review and meta-analysis. Frontiers in Sports and Active Living.

2. Finiel, L., Carron, S., Margot, C., et al. (2026). Energetic cost of locomotion closely aligns with the preferred uphill walk-run transition at constant vertical speed in runners. European Journal of Applied Physiology.

3. Martinez-Navarro, I., Vicente-Mampel, J., López-Grueso, R., et al. (2026). Uphill Walking Economy and Maximal Oxygen Consumption in Trail Runners: Relationship with Ultra-Trail Performance. International Journal of Sports Medicine.

4. Brill, J.W. & Kram, R. (2021). Does the preferred walk-run transition speed on steep inclines minimize energetic cost, heart rate or neither? Journal of Experimental Biology, 224, jeb233056.

5. Vernillo, G., et al. (2020). Steep (30°) uphill walking vs. running: COM movements, stride kinematics, and leg muscle excitations. European Journal of Applied Physiology.

6. Tanaka, H. (1994). Effects of cross-training: transfer of training effects on VO₂max between cycling, running and swimming. Sports Medicine.

7. Reilly, T., Morris, T. & Whyte, G. (2009). The specificity of training prescription and physiological assessment: a review. Journal of Sports Sciences.

8. Eihara, Y., et al. (2024). Effect of Strength Training Programs in Middle- and Long-Distance Runners' Economy at Different Running Speeds: A Systematic Review with Meta-analysis. Sports Medicine.

9. Recent umbrella review (2025). The Effect of Strength Training on Endurance Performance Determinants in Middle- and Long-Distance Endurance Athletes.

Mental toughness in ultrarunning is often misunderstood.

It isn’t about ignoring pain, refusing to walk, or proving how much suffering you can tolerate. Current research suggests the more useful skill is how you respond when things become difficult.

In this episode, I look at what the evidence tells us about mental toughness, pain coping, resilience and self-efficacy in ultra-endurance running and why stubbornness should not be confused with toughness.

We also explore a simple practical framework:

Acknowledge. Assess. Act.

Recognise what is happening, work out what you can control, and take the next useful action.

Because sometimes mental toughness means pushing. Sometimes it means slowing down, eating, walking, adapting the plan or fixing a problem early.

The goal isn’t to become unbreakable.

Mental toughness isn’t about suffering more. It’s about responding better.

Key references:

1. Song, Q., & Song, Y-G. (2026). Psychological Traits Associated with Mental and Performance Resilience in Long-Distance and Ultra-Endurance Runners: A Systematic Review. Frontiers in Psychology, 17, 1919146. DOI: 10.3389/fpsyg.2026.1919146.

2. Delalay, M., & Hotz Boendermaker, S. (2026). Mental Pain Responses of Ultramarathon Runners: A Scoping Review. Sports, 14(2), 72. DOI: 10.3390/sports14020072.

3. Paley, C. A., & Johnson, M. I. (2025). Human Resilience and Pain Coping Strategies: A Review of the Literature Giving Insights from Elite Ultra-Endurance Athletes for Sports Science, Medicine and Society. Sports Medicine, 55, 2137–2146. DOI: 10.1007/s40279-025-02277-4.

4. Alschuler, K. N., Krabak, B. J., Kratz, A. L., Jensen, M. P., Pomeranz, D., Burns, P., Bautz, J., Nordeen, C., Irwin, C., & Lipman, G. S. (2020). Pain Is Inevitable But Suffering Is Optional: Relationship of Pain Coping Strategies to Performance in Multistage Ultramarathon Runners. Wilderness & Environmental Medicine, 31(1), 23–30. DOI: 10.1016/j.wem.2019.10.007.

5. Brace, A. W., George, K., & Lovell, G. P. (2020). Mental Toughness and Self-Efficacy of Elite Ultra-Marathon Runners. PLOS ONE, 15(11), e0241284. DOI: 10.1371/journal.pone.0241284. Studied 56 elite HURT100 runners.