Caffeine is one of the most studied ergogenic aids in sports science, with well-established performance benefits. While caffeine can benefit many types of athletes, research shows that endurance athletes particularly benefit from caffeine.
But how exactly does caffeine help endurance performance? And how should endurance athletes use caffeine to maximize these benefits? Let’s dive into the science and strategy.
How Caffeine Improves Endurance Performance
Caffeine works by blocking adenosine, a molecule that gradually builds up during physical and mental exertion, leading to feelings of fatigue and drowsiness. Because caffeine has a similar structure to adenosine, it binds to the same receptors, effectively blocking adenosine from building up.
As a result, caffeine lowers the rate of perceived exertion (RPE). This means performance benefits such as:
- Less fatigue
- Improved alertness
- Elevated mood
Adenosine also plays a role in pain perception, so when it’s blocked, athletes may experience less discomfort during long or intense efforts.
In other words, caffeine makes exercise feel easier than it really is—allowing you to push harder for longer. These effects are particularly helpful during ultra-distance events, where performance might dip due to boredom, fatigue or pain.
Other Possible Benefits of Caffeine
In addition to blocking adenosine, caffeine may have other performance benefits. However, these benefits are not as well-supported by research, especially for endurance athletes.
Boost Carbohydrate Utilization
Some research shows that caffeine may enhance the body’s ability to use ingested carbohydrates during exercise—also known as exogenous carbohydrate oxidation. This theoretically could provide more rapid energy to muscles during prolonged effort.
For example, one study found that cyclists who consumed a 6% glucose solution with caffeine oxidized carbohydrates 26% more efficiently than those consuming glucose alone.
However, the overall evidence is limited and mixed, and it’s not yet clear whether it leads to meaningful performance improvements in real-world endurance scenarios.
Increased Fat Oxidation
Some research shows caffeine raises levels of catecholamines (including adrenaline), which promote fat oxidation. The increased fat oxidation theoretically means more available energy, thus sparing glycogen and delaying fatigue.
In the past, this was considered to be a key benefit of caffeine. However, this benefit is most pronounced during low and mid-intensity exercise, and in untrained and less-trained individuals. There does not seem to be any real-world benefit for highly-trained endurance athletes, especially at high-intensities.
Muscle Recruitment
Caffeine may also directly enhance how muscles contract: it may enhance calcium release within muscle cells, improve nerve impulse transmission, and lower the threshold for muscle fiber activation.
Research, such as this meta-analysis and this separate analysis, backs up these benefits for strength athletes, such as powerlifters. However, the research isn’t as clear whether this translates into benefits for endurance athletes.
Reminder: While caffeine can make exercise seem easier, our bodies still need energy. Make sure you prioritize your fueling strategy since this is ultimately what allows your body to keep going.
How Much Does Caffeine Improve Endurance Performance?
The research consistently shows that caffeine increases endurance performance. According to the International Society of Sports Nutrition (ISSN) official position, consuming 3–6 mg of caffeine per kilogram of body weight can improve endurance performance by 2–4%.
At the elite level, even a 1% boost can be the difference between winning and losing—so a 2–4% gain is significant.
Some studies report even greater improvements. One meta-analysis found that caffeine enhanced endurance performance by 2–7%. Another analysis focusing on time trials showed gains of up to 15.9%: the longer the time-trial, the larger the benefits.
Problems with Caffeine Research
It’s important to realize that, even though caffeine is widely-studied and has “proven” benefits for athletes, the research isn’t as clear as it might seem.
The first problem has to do with the placebo effect. As Dr. Tim Podlogar mentions during the Nduranz caffeine podcast episode, most athletes will know whether they’ve received caffeine or the placebo—meaning it is difficult to create a truly blind study.
Another problem is that there is surprisingly little research about how caffeine affects regular users. The effects on an athlete who drinks four espressos per day would be very different than an athlete who never consumes caffeine, making it difficult to establish benefits and a proper dosage.
Finally, most studies test caffeine in lab settings using treadmills or stationary bikes with fixed resistance. Since caffeine can cause athletes to push harder than they normally would, it is unclear how caffeine would affect long-term performance in real-world scenarios.
Is Caffeine Legal? Caffeine was banned by the IOC in 1984 and by WADA in 2000. Both organizations removed caffeine from their banned substances list in 2004. However, WADA still encourages athletes to maintain urine levels of 12 μg/ml, which corresponds to 10mg/kg of bodyweight—much higher than the recommended dosage amount. The NCAA still categorizes caffeine as a banned substance, but only if urine levels exceed 15 μg/ml.
Caffeine Risks for Endurance Athletes
Discussions about caffeine and performance usually focus on the benefits. However, caffeine can harm performance because of its side effects and possible impact on recovery and sleep.
- Side Effects: Caffeine exacerbates the effects of adrenaline. When you are already feeling amped up on race day, this can make you feel even more anxious and jittery. In large dosages, it can also cause stomach issues and a sudden need to go to the bathroom. None of these side effects will help you win a race.
- Impaired Recovery: Caffeine allows athletes to push harder than they normally would, which can cause them to burn through glycogen stores, hindering recovery.
- Sleep Cycle Disruption: Consuming too much caffeine, especially late in the day, can impact your sleep cycle which in turn can impact recovery, overall health, and performance.
Pro Fact: Caffeine Doesn’t Cause Dehydration. Nutritionists often advise refraining from caffeine because it is a diuretic. However, research shows that exercise counteracts this effect, and caffeine usage won’t result in dehydration or electrolyte imbalance.
Caffeine Guidelines for Endurance Performance
To get the performance benefits of caffeine capsules or fuel with caffeine while avoiding risks, follow these guidelines.
1. Establish Your Baseline
Caffeine dosage for endurance performance is typically 2-4 mg of caffeine per kilogram of body mass taken before exercise.
However, if you are a regular caffeine consumer, your dosage will be different than someone who rarely consumes caffeine. Dr. Tim Podlogar recommends establishing your baseline, and then adding the recommended dosage on top of this baseline.
Also read: Caffeine Ingestion Protocol for Endurance Athletes
Pro Fact: Research shows that while some people can tolerate high doses of caffeine, there does not seem to be any performance benefits to taking more than 6mg/kg of caffeine.
2. Top Up during Long Events
Caffeine has a half-life of 3-5 hours, meaning half of it will be removed from the body within this time period. If you take it before the start of a long event, its effects will start to dwindle. Because of this, it is generally recommended that you top up caffeine with 1 mg/kg per hour in events lasting 2+ hours.
Nduranz makes an Nrgy Gel 45 with Caffeine, allowing you to fuel and top up caffeine simultaneously.
The image above shows caffeine levels in the bloodstream with and without topping up. The dotted line is the threshold required for performance benefits.
3. Save Caffeine When You Want the Effects
It takes approximately 15 to 30 minutes for caffeine to reach peak concentrations in the bloodstream. Instead of topping off caffeine during the entire event, Dr. Tim Podlogar recommends timing caffeine intake for when you want to feel the boost of caffeine.
“It all like comes down to the task. For instance, you’ve got professional riders who want to respond to attacks and go into the break very early in the race, whereas others save caffeine for the last climb.”
4. Don’t Use Caffeine in Training
Save caffeine for race day. Using it to push through tough training sessions can lead to overexertion and compromise recovery. Over time, this increases the risk of overtraining.
Caffeine’s performance benefits also decline with regular use, so relying on it during training can reduce its effectiveness when you need it most—on race day.
The exception? When you're testing your race-day strategy.
5. Test Your Race Day Strategy
Because caffeine can have some serious side effects, you should always test your caffeine strategy before race day. This allows you to see how your body will tolerate the caffeine and adjust the dosage if necessary to avoid side effects.
Remember that you should also test your fueling strategy as well! You don't want any surprises on race day.
6. Avoid Using Caffeine Late in the Day
Be cautious with caffeine if you have a late start time, especially during stage races. It might boost your performance during the event, but it can also interfere with sleep—hurting your recovery and your performance the next day.
However, there are exceptions: If you are doing an ultra event that lasts 12+ hours or goes throughout the night, you might want to avoid pre-caffeinating and instead save your caffeine for late at night when mental fatigue sets in.
Also read: Nutrition Strategies for Ultra-Distance Races
7. Use the Right Form of Caffeine
Not all caffeine sources are equally effective for endurance performance. The goal is predictability. The form you choose should allow for effective dosing without side effects.
- Caffeine Capsules: These are ideal for precision dosing. They deliver a known amount of caffeine and are fast-acting, making them a great choice for pre-race loading or timed boosts during long events. However, capsules lack carbohydrates, so they need to be paired with proper fueling.
- Caffeinated Gels: These allow you to top up energy and caffeine at the same time. They're especially useful during events lasting longer than 2 hours, when both fuel and caffeine levels need to be maintained.
- Sports Drinks with Caffeine: While convenient for athletes who prefer sipping to chewing or swallowing capsules, the dosage is harder to control, especially if you want to time the boost for a specific task.
- Coffee: The amount of caffeine in coffee varies drastically, which makes dosing difficult. For perspective, one study of 97 espresso samples found caffeine amounts ranging from 25-214mg!
- Cola: Cola is somethings used as a fuel and caffeine source, but elite athletes tend to avoid it because its acidity and carbonation can lead to GI side effects, and because it does not contain the ideal 1:0.8 ratio of carbohydrates.
Ready for a boost? Nduranz Caffeine Capsules contain 50mg of pure caffeine anhydrous per capsule, and Nduranz Nrgy Gels with Caffeine are available with 65mg or 130mg of caffeine per gel, along with 45g of rapid carbohydrates in the ideal 1:0.8 ratio.
Want to learn more about caffeine for endurance performance? Watch the podcast episode below.
