Energy Gels: A Complete Guide to Choosing the Best Fuel for Your Workout

Running a half-marathon, completing rounds of Hyrox, a long bike ride, or tackling an ultra-trail: whatever the sport, energy management remains one of the most crucial performance factors. Beyond a certain intensity or duration, the body's energy reserves alone are no longer sufficient. This is precisely where energy gels come in, having become an essential part of sports nutrition.

Practical, concentrated, and easily transportable, they provide a quick energy boost where it's most needed: in the thick of the action. But you still need to know which one to choose, when to take it, and how to integrate it into your refueling strategy. This guide answers all these questions.

Before discussing dosage or timing, it's useful to understand what an energy gel truly is, how it works in the body, and why it has found such a central place in athletes' habits.

An energy gel is a dietary supplement in semi-liquid or viscous form, packaged in small individual doses (generally between 30 and 50 g). Its composition is primarily based on rapidly absorbed carbohydrates, designed to provide quickly available energy to active muscles. Unlike a solid meal, the gel does not require lengthy digestion: its nutrients quickly pass into the bloodstream to fuel muscle cells where the effort demands it.

This concentrated format is designed to be consumed on the go, without interrupting the effort. It addresses a specific physiological constraint: during intense or prolonged exercise, the body draws on its glycogen reserves stored in the muscles and liver. These limited reserves can be gradually depleted. Without external intake, performance inevitably declines.

Energy gels are not just for elite athletes. They are suitable for all profiles as long as the effort exceeds a certain duration or intensity.

Beginner athletes starting their first half-marathons or long-distance cycling can definitely integrate a gel into their nutritional strategy, provided they choose a simple formula and test it during training. Regular athletes who train several times a week and compete will find gels a precise tool to optimize their performance during long or intense sessions. Experienced athletes, whether preparing for a marathon, a Hyrox, an ultra-trail, or a long-distance triathlon event, will incorporate gels into a comprehensive and planned refueling strategy.

In summary, the question is not whether one is athletic enough to use a gel, but whether the nature and duration of their effort justify carbohydrate intake during activity.

The benefit of energy gels lies in their rapid action and practicality. In running, cycling, trail running, or triathlon, athletes cannot afford to pause for a snack. The gel is swallowed in seconds, without chewing, and its effect is felt within minutes.

Beyond practicality, the primary justification is physiological. Studies on nutrition during exercise show that carbohydrate intake during exercises lasting more than 60 to 90 minutes helps maintain blood sugar levels and preserve performance. A study published in Nutrition (20(7-8), 669-667) (Jeukendrup, 2004) showed that an intake of 30 to 60 g of carbohydrates per hour is associated with maintaining endurance during long efforts. The energy gel is one of the most effective ways to achieve this sports refueling goal.

The market now offers several variants of gels, each meeting specific needs:

• Standard gels, based on maltodextrin and/or glucose, provide rapid energy and form the basis of most formulas.
• Isotonic gels are formulated for rapid digestion, their concentration being similar to that of bodily fluids. They do not require dilution, but still need to be accompanied by regular water intake during exercise, at a rate of approximately every 15 to 20 minutes.
• Caffeinated gels contain varying amounts of caffeine, usually between 30 and 75 mg, to support alertness and delay fatigue throughout the effort.
• Electrolyte gels also provide minerals such as sodium or potassium, useful for compensating for losses due to sweating.
• Caffeine-free gels, with optimized formulas, focus on the quality of carbohydrates and complementary active ingredients rather than stimulation. Impulse Nutrition's energy gel belongs to this category: designed for efforts exceeding one hour, it combines 30 g of carbohydrates in a 50 g format, a glucose:fructose ratio of 1:0.8 for absorption through two different pathways, 157 mg of sodium, and a B6/B12 complex, with B6 contributing to the reduction of fatigue and B12 to normal energy metabolism, without stimulants or strong flavors.

The usefulness of a gel is not limited to replenishing sugars. Its effects are manifold, and it is interesting to understand them to better anticipate what to expect.

The main benefit of energy gel is to maintain a constant supply of carbohydrates during physical activity. When muscles work intensely, they consume glycogen at a high rate. This muscle store, with an average capacity of approximately 400 to 500 g, can be depleted in 90 minutes during sustained effort. The gel provides an external supply of carbohydrates that supplements these reserves, without waiting for them to run out.

Assimilation is rapid thanks to the nature of the carbohydrates used, mostly high glycemic index sugars. Some formulas combine several types of carbohydrates, such as glucose and fructose, to exploit different absorption pathways and increase the rate of assimilation. Studies by Jentjens & Jeukendrup (2005, British Journal of Nutrition) have shown that the combination of glucose and fructose can increase.

Fatigue during prolonged effort is not solely muscular. It is also cerebral. A drop in blood sugar affects concentration, decision-making, and motivation, parameters that are particularly important in trail running or triathlon, where mental strength plays as decisive a role as physical ability. By maintaining a regular supply of carbohydrates, the gel follows the same logic as carbohydrate-electrolyte solutions associated with maintaining endurance performance, including blood sugar.

Some gels containing caffeine add an extra dimension: caffeine is known for its ability to reduce perceived effort and maintain alertness, a relevant support at the end of a long event. For athletes who prefer to avoid stimulants, or who already manage their caffeine intake through other sources, gels enriched with vitamins B6 and B12, like Impulse Nutrition's, offer an alternative: B6 helps reduce fatigue, B12 supports the normal functioning of the nervous system, without a stimulating effect.

The impact of carbohydrate refueling on performance is well-documented in scientific literature. A meta-analysis (Vandenbogaerde & Hopkins, 2011, Sports Medicine) associates carbohydrate consumption during exercise with maintaining performance during exercises longer than 45 minutes, in line with the European claim on carbohydrate-electrolyte solutions.

For events exceeding two to three hours, such as a marathon, a cyclosportive, or an ultra-trail, this strategy becomes a central pillar of performance.

The energy gel is part of a broader nutritional strategy during exercise, which includes drinks, bars, or gels depending on the phases of the event. It does not replace a complete diet but is a precise tool for critical moments of effort.

Understanding the composition of a gel allows you to choose the formula best suited to your needs and avoid unpleasant surprises, especially concerning digestion.

Carbohydrates are the basic ingredient of any energy gel. Most often, they contain maltodextrin, a complex carbohydrate derived from corn or wheat starch, which has a high glycemic index while being easier to digest than pure glucose. Some gels also use glucose, fructose, or cane sugar, each with a different absorption profile.

The trend in modern formulas is to combine several carbohydrate sources to maximize intestinal absorption. Fructose, in particular, takes a different pathway from glucose in the intestine, which increases the total amount of carbohydrates assimilated per hour. This approach is particularly relevant for efforts lasting more than two hours. A well-formulated gel like that from Impulse Nutrition takes this principle to its optimum: 30g of carbohydrates in a 50g format, one of the highest concentrations on the market, with a 1:0.8 ratio between glucose and fructose to simultaneously exploit both intestinal absorption pathways.

Sweating leads to a loss of minerals, especially sodium, potassium, and magnesium, which play a key role in muscle contraction and fluid balance. Some gels incorporate electrolytes to compensate for these losses and support good sports hydration.

The presence of sodium is particularly important: it compensates for sweat losses and, combined with carbohydrates in a diluted solution, promotes water absorption in the intestine. For very long and intense efforts, an electrolyte-enriched gel helps compensate for mineral losses due to perspiration and supports fluid balance, a factor often associated with muscle comfort over time.

Beyond gels, electrolytes are also available in other convenient formats. Electrolyte sachets, to be diluted in a water bottle or flask, allow you to customize your sports drink throughout the event. Effervescent tablets or powders, like those offered by Impulse Nutrition, provide a quick-to-prepare, easy-to-carry, and pleasant-to-consume solution, particularly appreciated during daily training or as a supplement to gels over long distances. These formats naturally integrate into a complete refueling strategy, where the gel covers peak efforts and electrolytes ensure continuous mineral balance.

Caffeine is one of the most studied active ingredients in sports nutrition. Its main mechanism of action is based on blocking adenosine receptors in the brain, a molecule that induces feelings of fatigue. By delaying this signal, caffeine helps maintain alertness and reduce the perception of effort.

Meta-analyses grouping several dozen studies (Grgic et al., 2020, published in the British Journal of Sports Medicine) have confirmed a significant effect of caffeine on endurance performance. Effective doses are generally between 3 and 6 mg per kilogram of body weight. A gel containing 50 mg of caffeine therefore represents a moderate dose, suitable for targeted use during exercise. Caffeine helps improve concentration, endurance, and reduce perceived fatigue during physical exertion, in accordance with EFSA recognized claims.

Some formulas go beyond the carbohydrate-electrolyte-caffeine trio to incorporate B vitamins, particularly vitamin B6 and vitamin B12, which contribute to normal energy metabolism and help the body utilize the carbohydrates provided. B6 also helps reduce fatigue, while B12 supports the normal functioning of the nervous system, a particularly relevant support for long efforts where mental fatigue accumulates.

This is the approach adopted by Impulse Nutrition in its energy gel, which combines this B6/B12 complex with a caffeine-free formula, for effort support without stimulants. Other gels add antioxidants like vitamin C to limit oxidative stress generated by intense effort. These complementary active ingredients remain secondary in the overall composition, but they can provide added value for very long efforts, where metabolic stress is significant.

If you wish to discover an example of a formula meeting these criteria, Impulse Nutrition energy gel has been developed to support endurance efforts of more than one hour. It provides 30g of carbohydrates per gel, combines a glucose:fructose ratio of 1:0.8 to optimize carbohydrate absorption, as well as 157mg of sodium and vitamins B6 and B12. Its fluid texture and neutral taste have been designed to facilitate consumption during exercise.

Timing is as important as composition. Taking a gel at the right time optimizes its effect; consuming it too early or too late can reduce its benefit, or even cause discomfort.

Taking a gel before exercise is less common and should be considered carefully. If glycogen reserves have been adequately replenished by food in the preceding hours, a pre-exercise gel is generally not necessary. However, in the case of a morning workout on an empty stomach or when the previous meal was more than four hours ago, a gel taken 15 to 20 minutes before starting can stabilize blood sugar and aid in kick-starting performance.

It is important to be mindful, however: some individuals react to a rapid rise in blood sugar before exercise with reactive hypoglycemia at the beginning of activity. This phenomenon suggests testing this protocol during training before adopting it in competition.

This is the most logical and documented time to take it. For efforts lasting longer than 45 to 60 minutes, a first gel can be consumed between 30 and 45 minutes after starting, even before feeling fatigue. Waiting for the first signs of exhaustion to refuel is a common mistake: at this stage, reserves are already low and blood sugar recovery will take several minutes.

Subsequently, intake can be repeated every 30 to 45 minutes depending on the intensity of the effort and perceived needs. On a marathon or a long bike ride, this can represent four to six gels throughout the event, which corresponds to the usual recommendations of 40 to 60g of carbohydrates per hour.

Although gels are primarily designed for use during exercise, some athletes use them immediately after a session to initiate glycogen replenishment. This metabolic window, which lasts approximately 30 minutes after exercise cessation, is favorable for carbohydrate absorption. However, other nutritional forms, such as recovery drinks combining carbohydrates and proteins, are generally more suitable for this phase.

Having the right gel in your pocket is not enough. Its effectiveness largely depends on how it is consumed, particularly the hydration that accompanies it.

The intake strategy varies depending on the duration of effort. For activity lasting less than an hour, a gel during exercise is rarely necessary if pre-session nutrition was adequate. Between one and two hours, one to two gels are generally sufficient, taken mid-activity and at the end. Beyond two hours, regular intake every 30 to 45 minutes becomes relevant to maintain performance.

Ideally, you should test your strategy during training, in conditions similar to those of competition, to refine the number of gels, timing, and preferred flavors. What works for one runner will not necessarily work for another, particularly due to individual differences in digestive tolerance.

Unless otherwise stated on the product, an energy gel should always be consumed with water. The sugar concentration of a classic gel is high, well above the concentration of bodily fluids. Swallowed without water, it can slow its own passage through the intestine and promote gastric discomfort.

The recommended amount of water is approximately 150 to 200 ml per gel, which is two to three generous sips. You should also not combine a gel with a sugary sports drink at the same time, at the risk of an overly concentrated carbohydrate intake and digestive overload.

Several errors are regularly made by athletes discovering gels:

• Waiting until exhaustion to take the first gel: at this stage, replenishment is too late to be fully effective.

• Consuming too many gels in too short a time: an excess of carbohydrates exceeds intestinal absorption capacities and can cause nausea, bloating, or digestive discomfort.

• Forgetting to drink water with a non-isotonic gel: this disrupts assimilation and can irritate the digestive system.

• Testing a new gel in competition without having experimented with it in training: digestive reactions can vary depending on the formula.

• Storing gels in a warm place for a long time before use, which can alter their texture.

A half-marathon generally takes between 1h30 and 2h30 depending on the level. Over this distance, the recommended intake is between 40 and 60 g of carbohydrates per hour, which corresponds to 3 to 5 gels depending on the duration of the effort and the number of kilometers to cover.

The first gel can be taken after 45 minutes of effort, then the subsequent ones every 30 to 45 minutes until the finish line. The exact timing of each intake therefore depends on the running pace rather than a fixed kilometer marker. The priority remains to choose a gel that is well-tolerated digestively, with a fluid texture, and to systematically take it near a water aid station.

The priority is to choose a gel that is well-tolerated digestively, with a fluid texture, and to systematically take it near a water aid station.

In a marathon, the refueling strategy is crucial. The famous wall at the 30th kilometer is largely associated with the depletion of glycogen reserves in runners who have not adequately managed their carbohydrate intake during the race. Regular intake every 30 to 40 minutes, starting from the 5th or 6th kilometer, helps to prevent this energy crash. Four to six gels are generally necessary depending on the pace and individual tolerance. The last two can contain caffeine to support concentration and motivation in the final kilometers.

Ultra-trail presents very specific constraints: efforts that can last from six to forty hours, significant elevation changes, variable weather conditions, and aid stations sometimes several hours apart. In these events, the energy gel is only one part of the nutritional strategy, which also includes solid foods, soups, and sugary drinks. Gels are primarily used during intense climbs or technical sections, when the appetite for solid food disappears. Formulas with electrolytes are particularly recommended in hot weather or in case of heavy sweating. Caffeine should be used sparingly to avoid disturbing sleep during very long night events.

Intermediate distance trail running, between 20 and 80 kilometers, combines the constraints of a marathon with elevation management that puts more strain on the muscles. Gels are particularly useful during ascents, when intensity suddenly increases and the body demands quick energy. Light, easily accessible formats from a hydration pack are preferred. Alternating gels with electrolyte sachets diluted in the water bladder is a coherent strategy combining energy intake and mineral balance.

Cycling allows for more flexibility in intake, as pedaling puts less strain on the digestive system compared to running. Long rides, often two to five hours, require a comprehensive refueling strategy combining gels, bars, and drinks. Gels are especially useful in the second half of the effort or during climbs, when intensity increases and the appetite for solid foods decreases. Caffeine-containing formats can be particularly useful at the end of a ride to maintain alertness, especially on technical descents.

Hyrox is a functional fitness competition that alternates running and strength exercises for a duration ranging from 60 to 120 minutes depending on the level. The effort is intense and continuous, with quick transitions between stations. In this context, energy gels can be useful, but their use must be considered differently from classic endurance sports. A single gel, taken just before the start or in the first third of the event, is generally sufficient. The priority remains not to overload the digestive system during core exercises, weightlifting, or burpees. Light gels, with a fluid texture and without excessive additives, are preferred.

CrossFit is practiced in short, very intense sessions, rarely exceeding 60 minutes. In this context, energy gel is not a systematic tool. Its use is justified primarily during competitions like the Open or qualifiers, where several WODs are chained together on the same day, or during particularly long and demanding sessions. A gel taken 15 to 20 minutes before an intense event can help start with optimal blood glucose levels. However, incorporating it into every standard training session is of little interest and can accustom the body to a fast sugar intake that is not very relevant outside of an effort context, with no real long-term benefit.

In triathlon, nutrition management is particularly complex. Transitions between swimming, cycling, and running leave no time for comfortable eating. The gel is an ideal format: quick to consume, requiring no preparation. In long events like long-distance triathlon, planning intake is fundamental: too little energy intake will lead to exhaustion; too much will saturate digestion. Alternating gels and isotonic sports drinks, tested during training, forms the basis of a solid strategy.

For profiles ranging from half-marathon to ultra-trail, including Hyrox, cycling, and triathlon, Impulse Nutrition gels are designed to precisely cover efforts lasting over an hour: a fluid texture designed to pass even at high intensity, a neutral taste that maintains palatability over long distances, and a stimulant-free formula that integrates into any refueling strategy.

The question comes up often, and the answer is not universal. The choice depends on the athlete's profile, the duration of the event, and the timing of the effort.

Caffeine-enriched gels offer a dual effect: carbohydrate intake for muscle energy, and mental stimulation provided by caffeine. In long efforts, mental fatigue gradually sets in and can affect rhythm and motivation. Caffeine helps maintain concentration and push back this form of cognitive fatigue, a particularly valuable advantage in the final kilometers of a marathon or during the last stations of a Hyrox.

Caffeine also has the advantage of improving fat utilization as fuel, which helps spare glycogen reserves during long efforts. Studies show that this effect is particularly pronounced in trained athletes.

At the beginning of an effort, caffeine is not always necessary. It can even be counterproductive if the athlete is sensitive to stimulation: post-competition sleep disturbances, gastric irritation, or an unpleasant feeling of nervousness. Caffeine-free gels form the basis of the refueling strategy, and caffeine gels come as reinforcement at strategic moments.

People who are not used to consuming caffeine should also start with low doses and test their tolerance before integrating it into their competitive protocol.

An effective strategy is to consume caffeine-free gels in the first part of the event, then introduce a caffeine gel from two-thirds of the distance, when fatigue begins to set in. In a marathon with three to five gels in total, the first ones will be caffeine-free, and the last one or two will contain caffeine, adjusted according to the total planned. This alternation helps to avoid caffeine saturation and to reserve stimulation for when it is truly useful.

Here is a summary of the differences between the two types of gels:

With the diversity of available formulas, the choice can seem complex. A few simple criteria allow for effective guidance.

The primary criterion is carbohydrate content. An effective gel provides between 20 and 30 g of carbohydrates per serving. It is also important to check the sources used: the presence of a glucose and fructose combination is an indicator of an optimized formula for absorption. Also, look for the presence of electrolytes, especially sodium, particularly for efforts in hot weather or very long durations. As a reference, the Impulse Nutrition gel concentrates 30 g of carbohydrates in a 50 g format with a 1:0.8 ratio and 157 mg of sodium, one of the highest carbohydrate densities on the market, in a compact format.

The ingredient list should remain legible. Formulas with numerous, hard-to-pronounce components are not necessarily more effective. For athletes subject to anti-doping controls, verify that the product is certified according to EN 17444 standard, which guarantees the absence of prohibited substances.

Some athletes tolerate maltodextrin very well, while others prefer formulas combining fructose and glucose, or those based on sugars from natural sources such as dates or fruit puree, provided they test their individual tolerance to large amounts of fructose. The only way to know is to test several products during training, never during an important competition.

People with intestinal sensitivity should avoid gels with additives, sweeteners, or very high sugar concentrations. Simpler formulas with fewer ingredients are often better tolerated.

The texture plays a role in the comfort of consumption, especially during movement. Liquid gels are easier to swallow quickly; thicker gels sometimes require more water. The packaging format also matters: easy one-handed opening, a sachet that doesn't leak in the pocket – these are details that make a difference on the field.

Flavors deserve attention. During a long effort, taste preferences change: what seems pleasant at first can become sickening after two hours. Varying tastes and alternating sweet and neutral can help maintain appetite for refueling throughout the event.

This table summarizes the main recommendations according to the athlete's profile:

• Jeukendrup, A.E. (2004). Carbohydrate intake during exercise and performance. Nutrition, 20(7-8), 669-677.
• Jeukendrup, A.E. & Moseley, L. (2010). Multiple transportable carbohydrates enhance gastric emptying and fluid delivery. Scandinavian Journal of Medicine & Science in Sports, 20(1), 112-121.
• Vandenbogaerde, T.J. & Hopkins, W.G. (2011). Effects of acute carbohydrate supplementation on endurance performance: a meta-analysis. Sports Medicine, 41(9), 773-792.
• Grgic, J. et al. (2020). Wake up and smell the coffee: caffeine supplementation and exercise performance. British Journal of Sports Medicine, 54(11), 681-688.
• Burke, L.M. et al. (2011). Carbohydrates for training and competition. Journal of Sports Sciences, 29(S1), S17-S27.
• 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. Journal of the Academy of Nutrition and Dietetics, 116(3), 501-528.