Caffeine is one of the most evidence-supported supplements for endurance performance, but ultrarunners need to use it strategically rather than simply taking more.

The key message is that caffeine is not fuel. Carbohydrates provide energy for the muscles; caffeine mainly helps with alertness, focus, motivation, and perceived effort. This makes it especially useful in long ultras, where mental fatigue, sleepiness, low mood, and poor decision-making can become as limiting as physical fatigue.

For shorter races, caffeine before the start can be useful. But in longer ultras, especially races lasting over 8–15 hours or through the night, it is often better to delay caffeine until the second half, the night section, or the final third, when its benefits are more valuable.

A practical starting point is 25–50 mg per hour once caffeine use begins, adjusted based on tolerance. Some runners may tolerate more, but higher doses increase the risk of stomach issues, anxiety, jitters, and sleep disruption.

The episode emphasises that caffeine should never replace proper fuelling. When energy drops, the first question should be: have I taken enough carbohydrates?

Main takeaway: Fuel with carbohydrates. Focus with caffeine. Caffeine is not the engine; it is the light you switch on when the road gets dark.

Key references:

• Guest, N. S. et al. (2021). International Society of Sports Nutrition Position Stand: Caffeine and Exercise Performance. Journal of the International Society of Sports Nutrition. Australian Institute of Sport. Caffeine: Performance Supplement Guide.
• Wang, Z. et al. (2022). Effects of Caffeine Intake on Endurance Running Performance and Time to Exhaustion: A Systematic Review and Meta-analysis. Nutrients.
• Shen, J. G. et al. (2019). Establishing a relationship between the effect of caffeine and duration of endurance athletic time trial events. Journal of Science and Medicine in Sport.
• Goldstein, E. R. et al. (2010). International Society of Sports Nutrition Position Stand: Caffeine and Performance. Journal of the International Society of Sports Nutrition.
• Benchetrit, S. et al. (2024). The effects of sleep deprivation and extreme exertion on cognitive performance in ultra-marathon runners.
• Martinez Gonzalez, B. (2022). Sleep Deprivation and Ultra-endurance Performance. University of Kent thesis.
• Office of Dietary Supplements, NIH. Dietary Supplements for Exercise and Athletic Performance: Health Professional Fact Sheet.

In this episode, we explore why many trail and ultra runners feel that their breathing is still under control, but their legs simply stop working.

The main idea is that ultra running is not limited only by cardiovascular fitness. It is also limited by local muscular endurance: the ability of the quads, calves, glutes and stabilising muscles to keep producing force for hours.

Climbing, descending and technical terrain all place specific demands on the legs. Uphills require repeated force production, downhills create muscle damage through braking and impact, and trails constantly challenge stability and control. This is why a runner can still have a strong aerobic engine but lose performance when the legs are no longer able to absorb, stabilise and push.

The episode explains that the solution is not simply more mileage. Runners need race-specific preparation: uphill muscular endurance, downhill conditioning, purposeful hiking, and consistent strength training.

Key message: Train the engine, but build the chassis. In ultras, strong legs protect good fitness.

Key references:

• Millet et al. 2011 — neuromuscular fatigue in mountain ultras.
• Bontemps et al. 2020 — downhill running and eccentric damage.
• Pradas et al. 2021 — ultratrail racing, muscle damage and neuromuscular function.
• Balsalobre-Fernández et al. 2016 — strength training and running economy.
• Llanos-Lagos et al. 2024 — updated systematic review on strength training and running economy.

This episode explains why running performance drops in hot conditions and why it is not simply a loss of fitness or lack of toughness. In the heat, the body has two jobs: keep running and protect itself from overheating. More blood is directed towards the skin for cooling, sweat rate increases, heart rate rises, and the same pace costs more energy.

The key message is that on hot days, effort matters more than pace. A pace that feels easy in cool weather may become moderate or hard in the heat. Trying to force normal pace often leads to overheating, dehydration, gut problems, and a major slowdown later.

If a hot race is expected, heat acclimation over 10–14 days can improve tolerance. But when a heatwave arrives suddenly, the goal is damage control: slow down early, reduce intensity, walk climbs sooner, use shade, cool aggressively, hydrate sensibly, and protect the gut.

Main takeaway: In the heat, do not fight for your normal pace. Manage your effort, stay cool, and slow down before your body forces you to slow down.

Key references:

• González-Alonso, J. 2007. The cardiovascular challenge of exercising in the heat. Journal of Physiology.
• Wingo, J. E., Ganio, M. S., & Cureton, K. J. 2012. Cardiovascular drift during heat stress: implications for exercise prescription. Exercise and Sport Sciences Reviews.
• Périard, J. D., Eijsvogels, T. M. H., & Daanen, H. A. M. 2021. Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies. Physiological Reviews.
• Racinais, S. et al. 2015. Consensus recommendations on training and competing in the heat. Scandinavian Journal of Medicine & Science in Sports.
• Racinais, S. et al. 2023. IOC consensus statement on recommendations and regulations for sport events in the heat. British Journal of Sports Medicine.
• Heathcote, S. L. et al. 2018. Reviewing practical heat acclimation strategies for endurance athletes. Frontiers in Physiology.
• Zurawlew, M. J. et al. 2018. Post-exercise hot water immersion elicits heat acclimation adaptations in endurance trained and recreationally active individuals. Frontiers in Physiology.
• Wierick, S. C. et al. 2025. Hydration Strategies in Ultra-Endurance Running. Sports Medicine - Open / PMC.
• Knechtle, B. et al. 2019. Exercise-associated hyponatremia in endurance and ultra-endurance performance. Medicina.
• Hoffman, M. D. et al. 2015. Sodium Intake During an Ultramarathon Does Not Prevent Muscle Cramping, Dehydration, Hyponatremia, or Nausea. Sports Medicine - Open.

In this episode of The Trail Running Briefing, we explore why choosing a race with purpose can be a powerful part of ultra-distance performance.

Training, pacing, fuelling, strength, and recovery all matter, but when a race becomes difficult, runners also need a strong reason to keep moving. Purpose gives suffering direction. It helps runners stay patient, calm, and committed when fatigue, bad weather, stomach issues, or doubt begin to take over.

The episode explains that purpose is not just emotion or motivation. It becomes useful when it shapes real behaviour: choosing the right race, training consistently, practising specific skills, respecting the demands of the course, and creating process goals that support the bigger reason.

The key message is simple:

Do not just choose the race. Choose the reason.

Because when the easy motivation disappears, purpose may be what helps you find one more step.

Key references:

• Teixeira, P. J. et al. (2012). Exercise, physical activity, and self-determination theory: A systematic review. International Journal of Behavioral Nutrition and Physical Activity.

• Williamson, O. et al. (2024). The performance and psychological effects of goal setting in sport: A systematic review and meta-analysis. International Review of Sport and Exercise Psychology.

• Healy, L., Tincknell-Smith, A., & Ntoumanis, N. (2018). Goal Setting in Sport and Performance. Oxford Research Encyclopedia of Psychology.

• Schiphof-Godart, L., Roelands, B., & Hettinga, F. J. (2018). Drive in Sports: How Mental Fatigue Affects Endurance Performance. Frontiers in Psychology.

• Méndez-Alonso, D. et al. (2021). Influence of Psychological Factors on the Success of the Ultra-Trail Runner. International Journal of Environmental Research and Public Health.

• Taylor, I. (2018). The Five Self-Determination Mini-Theories Applied to Sport. Loughborough University / Routledge chapter.

• Jeong, Y. H. et al. (2023). The application of Goal Setting Theory to goal setting interventions in sport: A systematic review. International Review of Sport and Exercise Psychology.

This episode explains why recovery is one of the biggest limiting factors in ultrarunning performance. The key idea is that training does not create fitness by itself, training creates stress, and recovery allows the body to adapt.

The episode challenges the common mistake of treating recovery as something you can buy or add at the end, such as massage, compression boots, red light therapy, or other gadgets. These tools may help some runners feel better, but they are secondary. They cannot compensate for poor training structure, under-fuelling, lack of sleep, or high life stress.

The four fundamental recovery pillars are:

Sensible training: protecting easy runs, using de-load weeks, and respecting race recovery.

Food: eating enough protein, carbohydrates, fats, and fuelling key sessions properly.

Sleep: the most powerful recovery tool, supporting repair, immune function, mood, and performance.

Stress management: recognising that work, family, emotional pressure, and life load all affect the same recovery system.

The practical message is that ultrarunners should stop asking, “How much training can I survive?” and start asking, “How much training can I absorb?”

Fitness is not built by the training you complete. It is built by the training you recover from.

Key references:

• Kellmann, M. et al. (2018). Recovery and Performance in Sport: Consensus Statement. International Journal of Sports Physiology and Performance.
• Thomas, D. T., Erdman, K. A., & Burke, L. M. (2016). Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance.
• Kerksick, C. M. et al. (2017). International Society of Sports Nutrition Position Stand: Nutrient Timing. Journal of the International Society of Sports Nutrition.
• Jäger, R. et al. (2017). International Society of Sports Nutrition Position Stand: Protein and Exercise. Journal of the International Society of Sports Nutrition.
• Walsh, N. P. et al. (2021). Sleep and the Athlete: Narrative Review and 2021 Expert Consensus Recommendations. British Journal of Sports Medicine.
• Dupuy, O. et al. (2018). An Evidence-Based Approach for Choosing Post-exercise Recovery Techniques to Reduce Markers of Muscle Damage, Soreness, Fatigue, and Inflammation: A Systematic Review With Meta-analysis. Frontiers in Physiology.
• Mountjoy, M. et al. (2023). 2023 International Olympic Committee’s Consensus Statement on Relative Energy Deficiency in Sport. British Journal of Sports Medicine.
• Charest, J. & Grandner, M. A. (2020). Sleep and Athletic Performance: Impacts on Physical Performance, Mental Performance, Injury Risk and Recovery. Sleep Medicine Clinics / PMC.

Tapering is not about resting, it’s about absorbing the training you’ve already done. After weeks or months of building fatigue through long runs and hard sessions, your body needs time to recover and convert that work into performance. Without a proper taper, you arrive at the start line carrying fatigue instead of fitness.

The goal of tapering is simple: reduce fatigue while maintaining fitness. This is done by lowering overall volume (typically over 2–3 weeks for ultras) while keeping some short, controlled intensity to preserve sharpness and running economy especially important for technical trail terrain.

Runners often make two key mistakes: doing too much (trying to “top up” fitness) or doing too little (losing rhythm and feeling flat). It’s also common to feel worse during the taper—heavy legs, low energy, or doubt—but this is a normal part of the process as the body shifts into performance mode.

The key is to trust the taper, maintain consistency with reduced load, prioritise recovery, and avoid unnecessary changes.

You don’t gain fitness in the final weeks, you allow it to show.

• Inigo Mujika & Sabino Padilla (2003) “Scientific bases for precompetition tapering strategies” Medicine & Science in Sports & Exercise
• Inigo Mujika (2010) “Intense training: the key to optimal performance before and during the taper” Scandinavian Journal of Medicine & Science in Sports
• Thomas D. Bosquet et al. (2007) “Effect of tapering on performance: a meta-analysis” Medicine & Science in Sports & Exercise →
• David C. Nieman (1998, 2000) Research on immune function and recovery
• Asker Jeukendrup Multiple publications on endurance performance
• Timothy Noakes (2012) “Lore of Running”
• American College of Sports Medicine (ACSM Guidelines)
• NSCA Essentials of Strength Training & Conditioning

Hydration in long trail running is not just about drinking water. It is about replacing enough fluid and sodium to stay functional as conditions, duration, and sweat losses increase. This episode explains why runners can drink plenty and still feel flat, thirsty, heavy, or cramp-prone when sodium intake does not match the demands of the session. It also unpacks the simple idea that water replaces volume, but sodium helps you retain and use that fluid effectively.

The episode then shows how this appears in real training, why many runners get it wrong by using the same plan in every condition or by drinking too much plain water, and how to build a more practical strategy based on weather, duration, and individual sweat loss.

Main takeaway: Hydration is not just water. On long runs, replace what you sweat, not just what you drink.

Key references:

1. American College of Sports Medicine. Exercise and Fluid Replacement.

2. World Athletics. Fluid Needs for Training, Competition, and Recovery in Athletes.

3. Gatorade Sports Science Institute. Hydration and Nutrition Considerations for Endurance Exercise in the Heat.

4. Gatorade Sports Science Institute. Sodium Ingestion, Thirst, and Drinking During Endurance Exercise.

5. Gatorade Sports Science Institute. Sweating Rate and Sweat Sodium Concentrations in Athletes: A Review of Methodology and Intra-/Interindividual Variability.

6. ACSM. 9 Facts About Hydration & Electrolytes.

7. Gatorade Sports Science Institute. Normative Data for Sweating Rate, Sweat Sodium Concentration, and Sweat Sodium Loss in Athletes.

8. Gatorade Sports Science Institute. Sodium-Free Fluid Ingestion Decreases Plasma Sodium During Exercise in the Heat.
   

HRV, or heart rate variability, is not a score that tells ultrarunners whether they are fit or unfit on a given day. It is a signal of how well the body is handling overall stress. That stress comes not only from training, but also from sleep, work, travel, fuelling, illness, and life outside running.

The key idea in the episode is that HRV is most useful when viewed as a trend, not as a single daily number. One low reading does not mean much on its own, but a drop over several days, especially alongside tired legs, poor mood, or bad sleep, can be an early warning sign that recovery is slipping.

The episode also explains that runners often misuse HRV by treating it like a green-or-red traffic light. Instead, HRV should be combined with how you feel, your sleep, resting heart rate, and how training is going. It can be especially useful for deciding whether it is the right day for a hard session or whether recovery should come first.

The main takeaway is this: don’t chase a perfect HRV score, use HRV to understand whether your body is absorbing training or just accumulating stress.Key references:

• Buchheit, M. (2014). Monitoring training status with HR measures: do all roads lead to Rome? Frontiers in Physiology.
• Esco, M. R., Flatt, A. A., Nakamura, F. Y., et al. (2025). Monitoring Training Adaptation and Recovery Status in Athletic Populations Using Heart Rate Variability. Sports Medicine / PMC review.
• Düking, P., Zinner, C., Reed, J. L., et al. (2021). Monitoring and adapting endurance training on the basis of heart rate variability monitored by wearable technologies: A systematic review with meta-analysis. Journal of Science and Medicine in Sport.
• Manresa-Rocamora, A., Sarabia, J. M., Javaloyes, A., et al. (2021). Heart Rate Variability-Guided Training for Enhancing Cardiac-Vagal Modulation, Aerobic Fitness, and Endurance Performance: A Systematic Review with Meta-Analysis. International Journal of Environmental Research and Public Health.
• Schmitt, L., Regnard, J., Parmentier, A.-L., et al. (2015). Monitoring Fatigue Status with HRV Measures in Elite Athletes: An Avenue Beyond RMSSD? Frontiers in Physiology.
• Sammito, S., Böckelmann, I., et al. (2024). Update: factors influencing heart rate variability – a narrative review. Frontiers in Physiology.
• Herzig, D., Eser, P., Omlin, X., et al. (2018). The Association Between Endurance Training and Heart Rate Variability: The Confounding Role of Heart Rate. Frontiers in Physiology.

Training fatigue is normal. Overtraining is not. And very often, what runners call “overtraining” is actually a mix of excessive load, poor recovery, and under-fuelling.

This episode explains the difference between normal fatigue, non-functional overreaching, true overtraining syndrome, and Relative Energy Deficiency in Sport, or RED-S. The key message is that not all fatigue is the same, and the solution depends on the cause.

For ultrarunners, the biggest risks often come from stacking hard training, life stress, poor sleep, and low energy availability for too long. Warning signs include persistent tiredness, loss of performance, poor recovery, low mood, repeated illness, hormonal disruption, and recurring injuries.

The practical takeaway is simple: monitor warning signs early, fuel properly for the work you are doing, and make recovery as deliberate as training. The goal is not to avoid fatigue, but to make sure it is recoverable.

Main takeaway: Your body does not adapt to training you survive. It adapts to training you can recover from.

Key references

• Meeusen et al. ECSS-ACSM consensus on overtraining syndrome.
• Mountjoy et al. 2023 IOC consensus statement on RED-S.
• Stellingwerff et al. Overtraining Syndrome and RED-S: shared pathways, symptoms and complexities.
• Saw et al. Subjective self-reported measures for monitoring athlete fatigue.
• IOC consensus on load in sport and risk of injury.

Training hard has its place, but harder is not always better. In this episode, we explore why the real value of a session is not just in the stimulus it provides, but in the recovery cost it creates.

For trail and ultra runners, going too hard too often can quietly reduce consistency, compromise quality, increase injury risk, and leave you too fatigued to absorb the training that actually matters.

The key message is simple: the best training is not the hardest training, but the training you can recover from and repeat.

Key references:

• Seiler S. What is best practice for training intensity and duration distribution in endurance athletes? 2010.
• Stöggl TL, Sperlich B. The training intensity distribution among well-trained and elite endurance athletes. 2015.
• Sperlich B, et al. The proportional distribution of training by elite endurance athletes. 2023.
• Casado A, et al. Training Periodization, Methods, Intensity Distribution, and Volume in Highly Trained Endurance Athletes. 2022.
• Jones CM, et al. Training Load and Fatigue Marker Associations with Injury and Illness. 2016.
• Drew MK, Finch CF. The Relationship Between Training Load and Injury, Illness and Soreness. 2016.
• Gabbett TJ. The training-injury prevention paradox. 2016.
• Kreher JB, Schwartz JB. Overtraining Syndrome: A Practical Guide. 2012.