Caffeine is a popular go-to supplement for many athletes. And for good reason. Not only is it the key component of one of the world’s most widely used legal drugs – I’m talking about coffee here people – it is also a sports supplement that is well supported by scientific evidence. Caffeine can offer a performance-enhancing benefit by providing a small, but worthwhile, enhancement of performance over a range of exercise situations from short-duration events right through to endurance events. In this podcast, I’ll look at the role of caffeine specifically in resistance exercise and outline what could be the minimum amount needed for a benefit.
Of all the popular sports supplements, caffeine is in the rare air of a select few supplements that have the evidence behind them to support a benefit. In fact, caffeine was one of the few supplements to get the tick in the 2018 IOC Consensus Statement on dietary supplements for use by high-performance athletes. And I’ll link to this document in the show notes https://bjsm.bmj.com/content/52/7/439
So, let’s go over a summary of those benefits. Caffeine use has been seen to improve endurance capacity such as exercise time to fatigue and endurance-based time-trial activities of varying duration. And this endurance benefit is seen across cycling, running, rowing and many other sports.
To put some numbers to those benefits, caffeine consumed during endurance exercise may enhance a cycling time-trial performance by between 3 and 7 percent. During short-term, maximal effort and repeated sprint tasks, caffeine taken around an hour before exercise results in performance gains of 3 percent for task completion time, mean power output and peak power output during anaerobic activities of 1–2 min in duration. While for repeat sprint performances during intermittent team game activities. a one to eight percentage improvement is typically seen.
So how much caffeine do you need to take? Although early research was conducted using high doses of caffeine (up to 6 mg and above of caffeine per kilogram of body weight), more recent research indicates that lower doses can provide similar performance benefits with fewer negative side effects. Individual responses to caffeine vary but typically doses in the range of 1 to 3 mg of caffeine per kilogram body weight are sufficient to improve performance.
But filling out those recommendations a bit more and applying them to a sport-specific situation, a recent review looked at the minimum effective dose of caffeine that could be needed for resistance exercise. Previous work in this area has found that there is a performance-enhancing effect of caffeine on muscular strength, endurance, velocity and power.
So, what is the minimum effective dose of caffeine needed to elicit an ergogenic effect in resistance exercise? This is an important question to ask considering very high doses of caffeine can cause fairly severe side effects such as increased heart rate, anxiety and over-arousal, sleep disturbances and gastrointestinal upsets.
A recent meta-analysis published in May of 2022 set out to answer the question of the minimum effective dose of caffeine in resistance exercise. In all, 12 randomised controlled trials involving over 200 healthy participants were included. And I’ll link to the study in the show notes. https://pubmed.ncbi.nlm.nih.gov/35203046
The caffeine doses in the included trials ranged from 0.9 to 2 mg/kg and were taken between 25 to 60 minutes before exercise. To put that dose of caffeine into context, for an 80 kg person, a dose of 1 mg/kg body weight of caffeine is what you would expect to find in a cup of coffee. Though more about coffee vs caffeine supplements near the end of this episode.
So, what were the findings of the review? Overall, low-dose caffeine was able to increase muscle strength and endurance and mean velocity. And the magnitude of these effects was similar to prior studies that used higher doses of caffeine.
So, it looks positive for caffeine yet again in sports. But a big disclaimer: Not everybody responds the same to caffeine and there is some evidence that this could be because of genetics where the presence or absence of genetic variations in a gene called CYP1A2 can mean a person is either a rapid or slow metaboliser of caffeine and this could explain some of the variation in responses to caffeine seen in clinical trials.
And then there is a potential issue of habituation. That is where for frequent and high dose caffeine consumers, higher doses of caffeine may be required to give the same physiological effect previously observed with lower caffeine doses. That’s another way of saying that everyone’s mileage will vary with caffeine.
So, how does caffeine work its magic? Caffeine is a stimulant that elicits many physiological and psychological effects in the body. While its mechanism of benefit is not fully understood, caffeine may enhance alertness, reduce the perception of fatigue, improve vigilance and alertness, and change the perception of work effort during exercise. It can also increase motor unit recruitment and muscle contractility making the whole musculoskeletal system work more efficiently. There are also neurotransmitter effects and increases in endorphin release which can increase feelings of wellness, and give you the exercise ‘high’ that people often experience after working out
Caffeine is readily absorbed and reaches peak concentration in the blood 1-hour after taking it and is maintained for 3-4 hours. So, it is the 60-minute window just before exercise that is the best time to take it and then ‘top-up’ with additional dosing during endurance events of several hours in duration.
If 1 to 2 milligrams of caffeine per kilogram of body weight is effective for resistance exercise, how does that translate to foods and beverages? A typical average espresso can contain around 100 mg of caffeine. But because the caffeine content of coffee can be quite variable then the use of caffeine tablets such as NoDoze are popular.
Then there are the popular energy drinks, energy shots and gels which can contain caffeine, in which case the caffeine dosage should be given on the label. For example, a Red Bull contains 80 mg of caffeine per can, but there are energy drinks that contain even higher doses. Tea, chocolate and cola can also be sources, but the amount of caffeine in them is much lower.
The research field of caffeine has mostly used it in a pure form, with very little research looking at ‘real world’ use by drinking coffee and for good reason as the caffeine content of coffee can be so variable. But there could be other beneficial chemicals in the coffee bean outside of the caffeine. The one point for budding athletes to be aware of is that the amount of caffeine in coffee can be quite variable, meaning it is hard to know exactly what dose a person is having.
Caffeine is one of the few nutritional supplements for which research has consistently shown a sports performance benefit. The use of all supplements and sports foods by athletes though involves a balance between the potential benefits set against potential risks such as health side-effects, anti-doping rule violations from contamination, and redirection of resources from real performance-enhancing factors. So, take this into account when considering taking any sports supplement. And seek out personalised advice from a sports dietitian. You can connect with an Accredited Sports Dietitian as well as access a great range of resources through the website of Sports Dietitians Australia at www.sportsdietitians.com.au
So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.
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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.