Caffeine and Performance in Ultrarunning

By Jason Koop
CTS Coaching Director, Author of “Training Essentials for Ultrarunning”

Several years ago while pacing my wife during the latter stages of the Run Rabbit Run 100 I vividly remember stumbling upon a ream of a dozen 200-mg caffeine pills. I wondered whether the runner who dropped the package was simply lazy and had not cut the foil-constrained ream down into more realistic chunks of a few pills, or actually intended to use all 2,400 mg of caffeine over the last 20 miles of the race. Because ultrarunners are a somewhat obsessive group, I assumed the latter. That would have been a sight! I’m glad I found the pills, and not an amped-up arrhythmic runner.

Can Caffeine Actually Improve Performance?

It turns out that caffeine can do more than help you wake up in the morning or beat afternoon sluggishness; it can act as an effective ergogenic aid when used appropriately. In a systematic review of 21 studies, researchers discovered around a 3.2% improvement in endurance performance (time trial performance, not time to exhaustion) with caffeine ingestion¹.

In addition to enhancing longer endurance performance, caffeine has been shown to improve efforts around 5 minutes in length at 90 to 100% of maximal oxygen uptake². New research even indicates there’s a genetic component to how you respond to caffeine. More on that later.

How Caffeine Improves Exercise Performance

While there has not been much doubt to the effectiveness of caffeine for endurance athletes, the mechanism by which it improves performance is less clear. A leading theory is that caffeine affects the brain and central nervous system, increasing alertness and focus and modulating central fatigue. Caffeine has also been shown to increase fat utilization in working muscles, thereby sparing muscle glycogen. This appears to have a more minor impact on performance, but it is measurable nonetheless.

How Genes Influence Individual Response to Caffeine

An athlete’s response to caffeine is related to how quickly it is metabolized in the body, and that rate is at least partly controlled by genetics. Those who metabolize caffeine more quickly experience the ergogenic effects of caffeine sooner after ingestion, the effects may ramp up more quickly, and you may reach the peak effect of caffeine sooner than athletes who metabolize caffeine more slowly. The effects of caffeine will subside sooner, as well. People who metabolize caffeine more slowly experience a more gradual ramp up of ergogenic effects, often respond to a lower amount of caffeine (have greater sensitivity to caffeine), and the effects of caffeine tend to last longer for this group. Slow metabolizers are the folks who don’t want to consume caffeine late in the afternoon because it keeps them up all night. Fast metabolizers can consume caffeine multiple times a day because the effects are shorter-lived.

For a long time, people have used simple trial and error to figure out how they respond to caffeine. Genetic testing adds a layer of data to this process and can help you optimize how and when you consume caffeine to achieve the ergogenic effect you’re after.

Caffeine and Ultrarunning

Caffeine supplementation in ultrarunning can be used in two ways: to acutely enhance your performance or as a stimulant specifically to stay awake and alert.

Caffeine as a performance enhancer

Caffeine supplementation starts with your morning cup of coffee on race day. If you regularly drink a cup or two a day, feel free to enjoy a similar amount as you go through your pre-race or pre-workout routine. This supplementation then changes, based on the race distance you are about to undertake.

For shorter races lasting less than six hours, you can supplement with occasional caffeine, up to 50 mg in any particular hour for the entire race. The supplementation should mainly come from caffeinated gels, chews, and colas. If you typically have coffee in the morning, caffeine from the coffee should be enough for the first two to three hours of the race. Therefore, I suggest waiting until after the second or third hour to start supplementing with caffeine in other forms. Furthermore, the dose-response from caffeine as it relates to endurance performance is not linear, meaning that moderate doses of caffeine are likely to have the same performance effect as higher doses (Graham and Spriet 1995). More isn’t always better. Thus, a cautious and conservative approach will have the same performance effect as a more aggressive one. As mentioned above, genetics may play a role in how quickly you experience an ergogenic effect from caffeine, and how long that effect may last.

Caffeine to stay awake and alert

Many ultrarunning events go into the night and through the following day. Runners are constantly battling the mythical-yet-real sleep monster, particularly in the wee hours of the morning, before sunrise and after 20 hours on their feet. Caffeine is one of the key pieces of ammunition against the sleep monster, and you can ingest it in many forms: pills, colas, teas, chocolate-covered espresso beans, energy drinks, and caffeinated sports nutrition products. However, when using caffeine as a stimulant to boost your alertness, the timing, rather than the form, is critical.

For athletes competing in events lasting longer than 24 hours, caffeine is best viewed as a stimulant to stay awake and alert. In these situations, you need to focus on when the stimulation will be needed most, and then supplement at that point. This means starting the day with a normal routine, including pre-race breakfast and coffee if that is what you are accustomed to. But as the race begins, take care to avoid caffeine. Gels, drinks, and foods at this point should all be non-caffeinated. Sometime after midnight, when you expect a visit from the sleep monster, begin your caffeine supplementation. Doses can be as high as 100 mg/hour for three to four hours and can cease shortly after the sun rises, which helps to reset your circadian rhythms.

How Much is Too Much?

The amount of caffeine needed to see performance enhancing effects is in the range of three to six milligrams per kilogram of body mass¹. A 75-kilogram (165-pound) athlete, at three milligrams per kilogram of body mass, would want to consume roughly 225mg of caffeine, which is a bit more than what’s in 16 ounces of coffee (200mg). On the high side of the range, the same athlete would aim to consume 450mg of caffeine. What about caffeine pills? They work, and a 1998 study showed they work a bit better than coffee, but in practical scenarios, they make it very easy for an athlete to overdo it with caffeine and experience jitteriness and nausea.

Caffeine May Help Improve Recovery

Caffeine may be able to quicken glycogen replenishment after a workout, but rapid glycogen replenishment is rarely a limiting factor in ultrarunning training. A post-exercise drink with 4 g/kg carbohydrate and 8 mg/kg caffeine showed a 66% increase in glycogen resynthesis when compared to a carbohydrate only drink⁵. This can be helpful for an athlete doing two workouts a day or on back-to-back days with an evening run the first day and morning run the second day. Typically, however, glycogen stores will be fully replenished within 24 hours from your normal diet, so I’d recommend skipping caffeine unless there’s a well-identified need for adding it to a post-workout nutrition strategy.

What Are the Drawbacks of Caffeine?

It’s important to acknowledge that you can over do it with caffeine and cause more harm than good. Doses of 9 mg/kg or more are likely to impair performance and cause side effects including “…anxiety, jitters, inability to focus, gastrointestinal unrest, insomnia, irritability, and, with higher doses, the risk of heart arrhythmias and mild hallucinations.”² Ultrarunners can get themselves into trouble with caffeine because of how long you’re on course. Ingesting 9 mg/kg of caffeine (675mg for a 75kg or 165lb athlete) at one time is as ridiculous as it sounds. That would be 3.4 caffeine pills or nearly half a gallon of coffee. However, since it can take up to 60 minutes to reach caffeine’s maximum effect on performance and alertness, and these effects can last for hours, athletes can unwittingly overload on caffeine by consuming reasonable amounts too frequently. It is not uncommon for athletes to make the mistake of continually a little more caffeine will help them stay alert in the last few hours of an ultramarathon, only to experience the negative effects of overconsumption instead.

An Ultrarunner’s Action Plan to See Benefits From Caffeine

1. Test different amounts of caffeine in training to see how your body responds. Consider incorporating genetic testing to add context to what you’re seeing from trial and error.
2. If using caffeine to improve performance in 50km or 50-miler, consume up to 50mg/hr in the second half of your event based on what has worked in training.
3. If using caffeine to improve alertness during a 100-miler:
   1. Avoid caffeinated products until performance is significantly threatened by feeling tired (not fatigued, but sleepy).
   2. Supplement with the amount shown to work in training, up to about 100mg/hr. Remember that more is not necessarily better.

¹ Ganio, Matthew S; Klau, Jennifer F; Casa, Douglas J; Armstrong, Lawrence E; Maresh, Carl M. Effect of Caffeine on Sport-Specific Endurance Performance: A Systematic Review. Journal of Strength & Conditioning Research:January 2009 – Volume 23 – Issue 1 – pp 315-324

² Spriet, Lawrence L. “Exercise and Sport Performance with Low Doses of Caffeine.” Sports Medicine 44.S2 (2014): 175-84.

³ Lopes JM, Aubier M, Jardim J, Aranda JV, Macklem PT: Effect of caffeine on skeletal muscle function before and after fatigue. J Appl Physiol: Respirat Environ Exercise Physiol. 1983, 54: 1303-1305.

⁴ Graham TE, Hibbert E, Sathasivam P: Metabolic and exercise endurance effects of coffee and caffeine ingestion. J Appl Physiol. 1998, 85: 883-889.

⁵ Pedersen DJ, Lessard SJ, Coffey VG, Churchley EG, Wootton AM, Ng T, Watt MJ, Hawley JA: High rate of muscle glycogen resynthesis after exhaustive exercise when carbohydrate is coingested with caffeine. J Appl Physiol. 2008, 105: 7-13. 10.1152/japplphysiol.01121.2007.