Carbohydrates are the foundation of fueling during endurance exercise. They help maintain energy levels, consistent muscle function and performance quality throughout training and competition.
In practice, runners, cyclists and triathletes most often use two types of gels:
-
caffeine-free gels,
-
caffeinated gels.
Although both provide energy, they should be used differently. Caffeine is not always the best option — especially when gut issues occur or high intensity continues for several hours.
Caffeine-free gels – the foundation of your fueling strategy
Caffeine-free gels should form the basis of most fueling strategies during exercise.
Their main purpose is to:
-
provide carbohydrates,
-
maintain stable energy levels,
-
support glucose availability for working muscles,
-
limit the decline in performance as exercise duration increases.
Why are caffeine-free gels so important?
During prolonged exercise, glycogen stores are gradually depleted and energy availability declines. A regular carbohydrate intake helps to:
-
maintain exercise intensity,
-
limit accumulating fatigue,
-
improve exercise tolerance,
-
support nervous system function.
That is why caffeine-free gels should be used regularly throughout exercise.
Benefits of caffeine-free gels
Predictable effects
Caffeine-free gels are generally better tolerated by the digestive system and provide a more consistent energy effect.
Lower risk of gut issues
The absence of caffeine means:
-
a lower risk of intestinal cramps,
-
a lower risk of exercise-induced diarrhoea,
-
less stimulation of the digestive system.
Suitable for regular use
They can be used:
-
from the start of exercise,
-
regularly every 20–40 minutes,
-
as the main energy source during training or competition.
How does caffeine work in an athlete’s body?
Caffeine is one of the best-researched ergogenic ingredients in sport. Unlike carbohydrates, it does not provide energy directly; its main effect is on the nervous system.
Caffeine’s primary mechanism of action involves blocking adenosine receptors in the brain.
What is adenosine?
Adenosine is a substance that gradually builds up during exercise and wakefulness. Its effects include:
Caffeine blocks the effects of adenosine, allowing the body to:
-
maintain concentration for longer,
-
feel fatigue more slowly,
-
tolerate high exertion better,
-
maintain intensity despite increasing strain.
In practice, an athlete often does not have “more energy” but feels less fatigued at the same exercise intensity.
Caffeine and central fatigue (CNS)
During prolonged exercise, fatigue is not limited to the muscles. The central nervous system (CNS) also plays an important role.
This central fatigue can lead to:
-
reduced concentration,
-
slower reaction times,
-
difficulty maintaining pace,
-
poorer tactical decisions,
-
reduced motivation to continue exercising.
Caffeine may partially limit these effects, which is why it is often used:
-
in the final stages of competition,
-
during long endurance sessions,
-
in sports requiring concentration and quick reactions.
Caffeinated gels – when are they most useful?
Caffeine works differently from carbohydrates alone.
Its main effect is on the nervous system, which means it may:
When should you use caffeinated gels?
They are most often used:
-
during the second half of exercise,
-
before a key moment in competition,
-
before an intense training segment,
-
towards the end of a race or match.
Practical examples
Running
-
the final stages of a half marathon or marathon,
-
the final kilometres of a trail run,
-
long tempo sessions.
Cycling
Triathlon
-
the final part of the bike leg,
-
the start of the run after cycling,
-
the second part of the race, when central fatigue builds.
When can caffeine be a problem?
Although caffeine may improve performance, it is not always the right choice.
Possible side effects include:
-
increased intestinal activity,
-
a laxative effect,
-
an increased risk of gastrointestinal issues,
-
a feeling of fluid sloshing in the stomach,
-
difficulty tolerating a high carbohydrate intake.
This is particularly important during:
-
high-intensity exercise,
-
high temperatures,
-
dehydration,
-
very prolonged exercise.
Test your caffeine strategy in training
“Never test anything new on race day” is one of the most important sports nutrition principles for runners, cyclists and triathletes.
A caffeine strategy should be tested during training beforehand, as individual responses can vary considerably.
For some athletes, caffeine may improve concentration and help maintain pace during the final phase of exercise. For others, it may cause:
What should you test beforehand?
The most common mistake – too much caffeine
In practice, many athletes:
This can lead to:
That is why caffeinated gels should complement your strategy, not form its foundation.
Polyphenols in endurance sport – how do they differ from caffeine?
Polyphenols are also receiving increasing attention in sports nutrition, particularly anthocyanins from Montmorency cherries.
Unlike caffeine, polyphenols do not stimulate the nervous system. Their role is primarily associated with supporting blood vessel function, blood flow, exercise tolerance and recovery after intense exertion.
For this reason, they are increasingly used to complement fueling strategies based on carbohydrates and caffeine, particularly in endurance sports, where recovery, limiting accumulating fatigue and maintaining a high quality of training and competition are all important.
What does a good strategy look like?
The following approach is generally the most effective:
Foundation
Caffeine-free gels:
-
regularly throughout exercise,
-
a consistent supply of energy,
-
maintaining carbohydrate availability.
Strategic addition
Caffeinated gels:
Summary
Caffeine-free and caffeinated gels serve different functions in an athlete’s fueling strategy.
Caffeine-free gels:
Caffeinated gels:
-
support concentration,
-
help delay central fatigue,
-
are most effective when used strategically during the final phase of exercise.
What matters is not only the amount of carbohydrates, but also the right timing of caffeine use, digestive tolerance and testing the strategy during training beforehand.
References
-
Spriet LL. Exercise and Sport Performance with Low Doses of Caffeine. Sports Medicine.
-
Ganio MS et al. Effect of caffeine on sport-specific endurance performance. J Strength Cond Res.
-
Burke LM. Nutritional approaches to counter performance constraints in high-level sports competition. Sports Medicine.
Caffeinated or caffeine-free gels? When to use caffeinated energy gels in endurance sports
Carbohydrates are the foundation of fueling during endurance exercise. They help maintain energy levels, consistent muscle function and performance quality throughout training and competition.
In practice, runners, cyclists and triathletes most often use two types of gels:
caffeine-free gels,
caffeinated gels.
Although both provide energy, they should be used differently. Caffeine is not always the best option — especially when gut issues occur or high intensity continues for several hours.
Caffeine-free gels – the foundation of your fueling strategy
Caffeine-free gels should form the basis of most fueling strategies during exercise.
Their main purpose is to:
provide carbohydrates,
maintain stable energy levels,
support glucose availability for working muscles,
limit the decline in performance as exercise duration increases.
Why are caffeine-free gels so important?
During prolonged exercise, glycogen stores are gradually depleted and energy availability declines. A regular carbohydrate intake helps to:
maintain exercise intensity,
limit accumulating fatigue,
improve exercise tolerance,
support nervous system function.
That is why caffeine-free gels should be used regularly throughout exercise.
Benefits of caffeine-free gels
Predictable effects
Caffeine-free gels are generally better tolerated by the digestive system and provide a more consistent energy effect.
Lower risk of gut issues
The absence of caffeine means:
a lower risk of intestinal cramps,
a lower risk of exercise-induced diarrhoea,
less stimulation of the digestive system.
Suitable for regular use
They can be used:
from the start of exercise,
regularly every 20–40 minutes,
as the main energy source during training or competition.
How does caffeine work in an athlete’s body?
Caffeine is one of the best-researched ergogenic ingredients in sport. Unlike carbohydrates, it does not provide energy directly; its main effect is on the nervous system.
Caffeine’s primary mechanism of action involves blocking adenosine receptors in the brain.
What is adenosine?
Adenosine is a substance that gradually builds up during exercise and wakefulness. Its effects include:
a feeling of fatigue,
reduced concentration,
increased sleepiness,
lower nervous system arousal.
Caffeine blocks the effects of adenosine, allowing the body to:
maintain concentration for longer,
feel fatigue more slowly,
tolerate high exertion better,
maintain intensity despite increasing strain.
In practice, an athlete often does not have “more energy” but feels less fatigued at the same exercise intensity.
Caffeine and central fatigue (CNS)
During prolonged exercise, fatigue is not limited to the muscles. The central nervous system (CNS) also plays an important role.
This central fatigue can lead to:
reduced concentration,
slower reaction times,
difficulty maintaining pace,
poorer tactical decisions,
reduced motivation to continue exercising.
Caffeine may partially limit these effects, which is why it is often used:
in the final stages of competition,
during long endurance sessions,
in sports requiring concentration and quick reactions.
Caffeinated gels – when are they most useful?
Caffeine works differently from carbohydrates alone.
Its main effect is on the nervous system, which means it may:
improve concentration,
increase alertness,
delay the perception of fatigue,
help maintain high intensity as exertion increases.
When should you use caffeinated gels?
They are most often used:
during the second half of exercise,
before a key moment in competition,
before an intense training segment,
towards the end of a race or match.
Practical examples
Running
the final stages of a half marathon or marathon,
the final kilometres of a trail run,
long tempo sessions.
Cycling
the final hour of a race,
before a climb,
before a decisive segment.
Triathlon
the final part of the bike leg,
the start of the run after cycling,
the second part of the race, when central fatigue builds.
When can caffeine be a problem?
Although caffeine may improve performance, it is not always the right choice.
Possible side effects include:
increased intestinal activity,
a laxative effect,
an increased risk of gastrointestinal issues,
a feeling of fluid sloshing in the stomach,
difficulty tolerating a high carbohydrate intake.
This is particularly important during:
high-intensity exercise,
high temperatures,
dehydration,
very prolonged exercise.
Test your caffeine strategy in training
“Never test anything new on race day” is one of the most important sports nutrition principles for runners, cyclists and triathletes.
A caffeine strategy should be tested during training beforehand, as individual responses can vary considerably.
For some athletes, caffeine may improve concentration and help maintain pace during the final phase of exercise. For others, it may cause:
intestinal cramps,
a feeling of fluid sloshing in the stomach,
excessive stimulation,
an increased heart rate,
difficulty tolerating a high carbohydrate intake.
What should you test beforehand?
the amount of caffeine,
when to take the gel,
combining caffeine with carbohydrates,
digestive tolerance,
your body’s response during high-intensity exercise.
The most common mistake – too much caffeine
In practice, many athletes:
use caffeine too early,
combine multiple sources of caffeine,
use caffeinated gels as the foundation of their strategy.
This can lead to:
gut issues,
excessive stimulation,
poorer exercise tolerance,
an energy “crash” towards the end of competition.
That is why caffeinated gels should complement your strategy, not form its foundation.
Polyphenols in endurance sport – how do they differ from caffeine?
Polyphenols are also receiving increasing attention in sports nutrition, particularly anthocyanins from Montmorency cherries.
Unlike caffeine, polyphenols do not stimulate the nervous system. Their role is primarily associated with supporting blood vessel function, blood flow, exercise tolerance and recovery after intense exertion.
For this reason, they are increasingly used to complement fueling strategies based on carbohydrates and caffeine, particularly in endurance sports, where recovery, limiting accumulating fatigue and maintaining a high quality of training and competition are all important.
What does a good strategy look like?
The following approach is generally the most effective:
Foundation
Caffeine-free gels:
regularly throughout exercise,
a consistent supply of energy,
maintaining carbohydrate availability.
Strategic addition
Caffeinated gels:
during the second half of exercise,
before a key moment,
as central fatigue begins to build.
Summary
Caffeine-free and caffeinated gels serve different functions in an athlete’s fueling strategy.
Caffeine-free gels:
provide energy,
support a consistent carbohydrate intake,
form the foundation of the fueling strategy.
Caffeinated gels:
support concentration,
help delay central fatigue,
are most effective when used strategically during the final phase of exercise.
What matters is not only the amount of carbohydrates, but also the right timing of caffeine use, digestive tolerance and testing the strategy during training beforehand.
References
Spriet LL. Exercise and Sport Performance with Low Doses of Caffeine. Sports Medicine.
Ganio MS et al. Effect of caffeine on sport-specific endurance performance. J Strength Cond Res.
Burke LM. Nutritional approaches to counter performance constraints in high-level sports competition. Sports Medicine.