Basic endurance in trail running is a term you will quickly hear about when you start getting interested in the sport! In this discipline, as in many endurance sports, we tend to think that progress means running faster, harder and longer. However, the most experienced trail runners know that progress is built first and foremost at low intensity. Admittedly, fundamental endurance can sometimes be perceived as a frustrating area of training and be underestimated, but it is a fact: it is essential for your body to provide you with reliability, endurance and resistance to fatigue in the field. 

Whether you are preparing your first trail race or whether you are looking to take your running to the next level over longer distances, understanding and incorporating fundamental endurance (FE) into your training will help you make a difference. 

What is fundamental endurance in trail running?

In practical terms, basic endurance corresponds to a comfortable pace that you can maintain for a long time without getting exhausted. At this intensity, your breathing remains calm, your effort is controlled and you could hold a conversation without being out of breath. In short, it's the pace at which you feel good! 

Physiologically speaking, you are mainly exercising in the aerobic zone. This means that your body produces the energy needed for exercise using oxygen, without generating excessive lactate build-up. This is an economical, sustainable way of functioning that is perfectly suited to the demands of trail running, where you exert yourself continuously for several hours. On hilly terrain, this concept becomes even more important. Your pace becomes secondary: what matters is the actual intensity of your effort, regardless of your speed.

Aerobic, anaerobic... what exactly are we talking about?  

When you run, your body uses two main energy systems. The aerobic system is responsible for endurance, duration and effort management. It allows you to run for long periods of time while limiting fatigue. Conversely, the anaerobic system kicks in when the intensity becomes too high: it is effective over short periods of time, but much more costly for the body.

And it is precisely our famous fundamental endurance that develops your aerobic capacity. The stronger this foundation is, the better you will be able to handle elevation changes, rack up the kilometres and recover quickly after the most demanding sections. It is like an invisible foundation that will then allow you to get the most out of more intense sessions without ending up completely flat out.

Why basic endurance really helps you improve your trail running

Working on your basic endurance can be harder than it looks. Why? Simply because when you feel good while running, you naturally want to push yourself a little further, telling yourself, ‘I can do this.’ Yes, forcing yourself to run slowly can make you feel like you're stagnating, but the opposite is true. In the long term, basic endurance: 

• Improves your heart's efficiency: training helps it build muscle, increasing its volume and thus sending more blood to your body... and therefore more oxygen to your muscles! 
• promotes the use of fats as the main fuel source. This is a major advantage in trail running, especially over long distances, where managing your energy reserves is ESSENTIAL.
• Develop your capillary network: this will also improve oxygenation to your muscles. 
• gradually strengthens muscles, tendons and joints, while limiting mechanical stress. The result: fewer injuries, greater consistency and much more sustainable progress.

How often should you run for basic endurance?

When it comes to trail running, basic endurance training should ideally make up the majority of your training programme. In a typical week, it should account for 70 to 80% of your total training volume, even if you are an experienced runner! Interval training and other intensive sessions should therefore make up the remaining 20 to 30% of your training time. 

The advantage of running for basic endurance is that since you put less strain on your body, you can afford to exercise more often. Two to three low-intensity runs per week is a good average for building a solid foundation. More intense sessions can then be added, but without taking over. The more you respect this balance, the more you will progress, almost without realising it! 

Whether trail running or training, how can you be sure to maintain your basic endurance?

The more you practise a sport, the more you learn to understand your body's signals. You can, of course, use your heart rate monitor connected to your smartwatch, but don't hesitate to trust yourself! The simplest way is to listen to how you feel. If you can talk without difficulty, if your breathing is smooth and if you feel you can keep going, you are in the right zone. Your heart rate can also be used as a guide: you should generally be between 65 and 75% of your maximum heart rate.

Finally, in trail running, it is perfectly normal (and even recommended!) to walk uphill to maintain this intensity. The goal is not to run at all costs, but to respect your cardiorespiratory system... and finish your run! 

What about managing elevation changes? 

The terrain is one of the classic pitfalls of trail running: a slightly steep climb and boom, you're pushing yourself too hard. Learning to slow down or walk, but also to shorten your stride (too long a stride is a classic beginner's mistake!), is an integral part of basic endurance training.

When going downhill, vigilance is also key. Going too fast greatly increases muscle and joint strain without providing any real cardiovascular benefit. Here again, control takes precedence over raw performance. Also, don't forget that a controlled downhill technique, for example, can be part of the marginal gains, and make a difference! 

How long should a basic endurance run last?

The duration depends on your level and your goal, but also on your physical condition. For a beginner, sessions of 30 to 45 minutes are already a very good starting point for rapid progress. However, be careful if you tend to injure yourself regularly! If you suffer from tendonitis, for example, something is wrong: lack of muscle strengthening, too much exercise for your level, unsuitable equipment... there are many possible reasons. In this case, unless advised otherwise by a doctor, start again gradually, beginning with sessions of around 20 minutes every 2 to 3 days. With experience, your sessions will gradually get longer and you'll be able to run for 1½ hours without noticing the time passing! 

Last but not least, these EF outings are ideal for developing your mental strength, testing your equipment and refining your nutrition strategy or your​ “trail” nutritiona plan, all without causing excessive fatigue.

Basic endurance, trail running and nutrition: there's so much to learn!

At low intensity, your body learns to use fat more efficiently as a source of energy. This ability to adapt is invaluable for trail running, where energy autonomy plays a major role. These basic endurance sessions are also perfect for testing simple nutritional strategies and ensuring that you tolerate them well. As your sessions get longer and you move on to pure trail running, you can treat yourself to one of our energy bars rich in good carbohydrates and lipids (every 45 minutes), our energy gels (without maltodextrin or glucose syrup, of course!) or our delicious​ energy purees, perfectly suited to intense exercise. In terms of hydration, in the field, our electrolyte tablets will give you a boost to recharge your batteries with essential minerals, vitamins and antioxidants. 

Everything you need to optimise your performance and go even further! 

the final word! 

Fundamental endurance in trail running is therefore the foundation of all progress. It allows you to run longer, recover better, limit injuries and fully enjoy your outings in nature. So even if the pace sometimes seems too slow, remember one thing: in trail running, it's always the strongest foundations that will take you the furthest!