Ultra distance cycling is one of the most extreme forms of endurance sport. Riders frequently spend 10, 20, or even more than 30 hours on the bike, often covering distances of 500 to 1000 kilometers in a single event. In races such as bikepacking ultras or multi-day endurance challenges, performance is determined not only by power output but also by energy management, metabolic efficiency, and resilience. For this reason, many endurance athletes experiment with fasted training. Also known as sobre training or training with low carbohydrate availability, sobre training involves performing specific workouts without eating beforehand in order to stimulate metabolic adaptations.
For ultra cyclists in particular, this strategy can offer several potential advantages. During ultra distance events, athletes often struggle with fueling because of limited food access, digestive issues, or sleep deprivation. Riders who can rely more heavily on fat as an energy source may therefore perform more consistently over long distances.
As an ultra distance cyclist myself, I typically include one or two fasted training sessions per week, usually early in the morning before breakfast. These rides are intentionally easy and focused purely on metabolic adaptation rather than performance.
This article explores everything you need to know about fasted training and ultra distance cycling, including:
- what sobre training is
- the science behind fasted endurance training
- why it may benefit ultra cyclists
- common mistakes to avoid
- practical implementation strategies
- a 12-week training structure
- frequently asked questions about fasted cycling training
What Is Fasted Training?
Fasted training refers to performing endurance exercise in a fasted state, usually after an overnight fast of approximately 8–12 hours.
In practice, this means doing a ride:
- early in the morning
- before eating breakfast
- at low intensity
During this state, the body’s liver glycogen levels are reduced, which shifts energy metabolism toward fat oxidation. Instead of relying primarily on carbohydrates, the body increases the proportion of energy derived from fat. This metabolic shift is the reason many endurance athletes use sobre training as a tool for improving endurance efficiency.
Research has shown that endurance training with low carbohydrate availability can enhance cellular signaling pathways related to mitochondrial biogenesis and metabolic adaptation (Bartlett et al., 2015). These adaptations may improve the body’s ability to sustain prolonged endurance exercise.
Energy Systems in Ultra Distance Cycling
Understanding the role of fasted training in ultra distance cycling requires understanding how the body produces energy during endurance exercise. The human body relies mainly on two fuel sources:
Carbohydrates
Stored as glycogen in muscles and the liver.
Advantages:
- rapidly available
- supports high-intensity efforts
Limitations:
- limited storage capacity
Most athletes store roughly 400–600 grams of glycogen, which equals around 1600–2400 kcal.
During moderate cycling intensity, glycogen stores may be depleted within several hours.
Fat
Stored in adipose tissue and muscle cells.
Advantages:
- extremely large energy reserve
- capable of fueling very long efforts
Limitations:
- slower energy release compared with carbohydrates
Even lean endurance athletes typically carry tens of thousands of calories in fat reserves.
For ultra distance cycling, this means fat is the only energy source capable of supporting extremely long efforts.
The purpose of sobre training is therefore to increase the body’s capacity to oxidize fat efficiently during endurance exercise.
The Science Behind Fasted Training
A growing body of research has investigated the effects of fasted training on endurance physiology.
Increased Fat Oxidation
Training in a fasted state has been shown to increase fat oxidation during exercise compared with training after carbohydrate intake (Van Proeyen et al., 2011). This means the body becomes more efficient at using fat as fuel. For ultra cyclists, this adaptation may help conserve glycogen during long events.
Mitochondrial Adaptations
Mitochondria are often described as the energy factories of muscle cells. Studies have demonstrated that training with low glycogen availability can increase mitochondrial enzyme activity and mitochondrial density (Hansen et al., 2005). More mitochondria means muscles become more efficient at producing energy during endurance exercise.
Enhanced Cellular Signaling
Training in a low-carbohydrate state activates important metabolic signaling pathways, including:
- AMPK
- PGC-1α
These pathways stimulate endurance adaptations and mitochondrial development (Bartlett et al., 2015). This is one reason many coaches believe occasional fasted training can amplify endurance adaptations.
Why Sobre Training Is Especially Relevant for Ultra Distance Cycling
Although fasted training is used by many endurance athletes, its potential benefits may be particularly relevant for ultra cyclists.
Extremely Long Race Durations
Ultra distance cycling events frequently last:
- 12–24 hours
- 24–48 hours
- multiple days
Even with consistent fueling, glycogen stores alone cannot support these efforts. Riders must rely heavily on fat metabolism. Training in fasted state may therefore improve metabolic efficiency over extremely long durations.
Fueling Challenges
Ultra cycling events often involve unpredictable fueling conditions. Athletes may experience:
- limited food availability
- reduced appetite
- digestive discomfort
Training occasionally without food can help athletes adapt psychologically and metabolically to these situations.
Stable Energy Levels
Cyclists with strong fat oxidation capacity often experience more stable energy levels during long rides. Instead of relying exclusively on carbohydrate intake, the body can tap into fat stores to maintain steady output.
Mental Resilience
Fasted training can also develop mental resilience. When you ride without breakfast, you learn how your body responds to hunger signals and energy fluctuations. For ultra distance cyclists, this mental familiarity can be extremely useful during long races.
My Personal Experience With Fasted Training
In my own ultra distance cycling training, sobre sessions are an important but controlled part of my weekly routine. I typically include 1–2 fasted rides per week.
Example structure:
- Wednesday morning
- 90 minutes fasted endurance ride
- Sunday morning
- 2 hour fasted endurance ride
These rides are performed at low intensity. They are not meant to improve speed or power. Instead, they are designed to train the body’s metabolic flexibility and fat oxidation capacity. After the ride, I eat a substantial recovery meal to restore glycogen and support recovery.
How to Implement Fasted Training Safely
Although fasted training can be beneficial, it must be implemented carefully.
Keep Intensity Low
Fasted training should remain in Zone 1 or Zone 2. Higher intensities require carbohydrate metabolism. Attempting interval training in a fasted state will usually compromise training quality.
Limit Duration
Most sobre sessions should last: 60–120 minutes. Occasionally they may extend to 2–3 hours, but this should be done cautiously.
Stay Hydrated
Hydration remains essential during fasted training. Water is usually sufficient, although black coffee or tea is also acceptable before the ride.
Refuel After the Ride
Post-ride nutrition is critical. A recovery meal should include:
- carbohydrates
- protein (20–30 g)
- micronutrients
Proper recovery helps maintain training quality throughout the week.
Common Mistakes With Sobre Training
Many athletes misuse fasted training. Here are some of the most common errors.
Doing High-Intensity Workouts Fasted
High-intensity workouts depend heavily on carbohydrates. Performing them fasted often leads to reduced performance.
Training Fasted Too Often
Excessive fasted training can lead to low energy availability, which may impair recovery and hormonal health. This condition is linked to Relative Energy Deficiency in Sport (RED-S) (Mountjoy et al., 2018).
Skipping Recovery Nutrition
Failing to refuel properly after a fasted ride can negatively impact recovery and subsequent workouts.
12-Week Fasted Training Plan for Ultra Distance Cycling
Below is a simplified progression for integrating fasted training into an endurance cycling program.
Assumption: cyclist trains 8–12 hours per week.
Phase 1: Adaptation (Weeks 1–4)
Goal: introduce fasted riding gradually.
Frequency:
1 fasted ride per week
Example week:
Monday – rest
Tuesday – intervals (fueled)
Wednesday – endurance ride
Thursday – recovery ride
Friday – rest
Saturday – long ride (fueled)
Sunday – fasted ride (60–75 min)
Phase 2: Metabolic Development (Weeks 5–8)
Goal: improve fat oxidation.
Frequency:
1–2 fasted rides per week
Example:
Wednesday – fasted ride (90 min)
Sunday – fasted endurance ride (2 hours)
Light fueling may begin after 90 minutes.
Phase 3: Ultra Specific Preparation (Weeks 9–12)
Goal: simulate ultra endurance demands.
Frequency:
2 fasted rides per week
Example:
Wednesday – fasted endurance ride (90 min)
Sunday – fasted ride (2–3 hours)
If fatigue accumulates, reduce frequency.
Combining Fasted Training With Proper Fueling
It is important to emphasize that sobre training should not replace proper fueling strategies. Ultra cyclists still need to train their nutrition.
This includes practicing:
- carbohydrate intake during long rides
- electrolyte management
- tolerance for solid foods
A useful principle often applied in endurance sports is: “Fuel for the work required.”
Meaning:
Hard workouts → fully fueled
Long rides → fueled strategically
Easy endurance rides → occasionally fasted
This balance allows athletes to gain metabolic adaptations without compromising performance.
Frequently Asked Questions About Fasted Training and Ultra Distance Cycling
What is fasted training in cycling?
Sobre or fasted training refers to performing endurance workouts in a fasted state, usually before breakfast. The goal is to increase fat oxidation and improve metabolic efficiency during endurance exercise.
Is fasted cycling good for ultra distance cyclists?
Fasted cycling can be useful for ultra distance cyclists because it may improve fat metabolism and metabolic flexibility. These adaptations can help riders sustain long efforts when carbohydrate availability is limited.
How often should cyclists do fasted training?
Most endurance coaches recommend 1–2 fasted rides per week. More frequent fasted training may impair recovery and increase the risk of low energy availability.
How long should a fasted ride last?
Typical fasted rides last 60–120 minutes. Advanced athletes may occasionally extend these sessions to 2–3 hours, but intensity should remain low.
Should you eat during a long fasted ride?
Yes. Even if a ride begins fasted, fueling may begin after 90–120 minutes during longer sessions.
Does sobre training improve endurance performance?
Sobre training may improve metabolic adaptations such as fat oxidation and mitochondrial development. However, it should be combined with proper fueling strategies and structured training to improve endurance performance.
Scientific References
Bartlett, J. D., Hawley, J. A., & Morton, J. P. (2015). Carbohydrate availability and exercise training adaptation. Cell Metabolism.
Hansen, A. K. et al. (2005). Skeletal muscle adaptation to training with low glycogen availability. Journal of Applied Physiology.
Mountjoy, M. et al. (2018). Relative Energy Deficiency in Sport (RED-S). British Journal of Sports Medicine.
Van Proeyen, K. et al. (2011). Training in the fasted state improves glucose tolerance during fat-rich diet. Journal of Physiology.
Yeo, W. K. et al. (2008). Skeletal muscle adaptation and performance responses to endurance training with low carbohydrate availability. Journal of Applied Physiology.
