Research Review: I’m hitting the weights rack, three cups of coffee please

A meta-analysis of caffeine consumption in relation to athletic and strength performance finds strong evidence for significant gains – but not for everyone and not without side-effects. Review by Assoc Prof Mike Climstein, PhD & Dr Joe Walsh, PhD

KEY POINTS

• Caffeine has easy passage to all biological membranes, with its peak effectiveness occurring from 30 minutes to two hours after consumption
• A meta-analysis showed exercise performance outputs of caffeine-consuming study subjects to be approximately 16% greater than those of subjects not taking caffeine
• For strength training, the most common dose of caffeine was 3 to 6 milligrams per kilogram of bodyweight taken
• The authors reported strength increases of up to 7% for muscular strength and muscular endurance
• Not everyone benefits performance-wise from consuming caffeine, and some negative effects, including anxiety and disrupted sleep, can occur in some individuals. 

Title: International Society of Sports Nutrition position stand: caffeine and exercise performance

Authors: Dr. Guest and colleagues (Faculty of Medicine, University of Toronto, Canada)

Source: Journal of the International Society of Sports Nutrition, 2021; 18: 1; 1-37. Read free online here.

Prologue: A long time ago in a galaxy far, far away… OK, that may be a little over theatrical; let’s try again. Over 22 years ago I was delivering lectures on ‘special populations’ as it was called back then, primarily on the topics of heart disease, osteoporosis and ageing. The audience for these lectures consisted of fitness enthusiasts studying to be fitness leaders and personal trainers at ‘Network for Fitness Professionals’ in Sydney. A colleague and surf buddy of mine, Liz Dene (a respected figure in the fitness industry), said to me ‘Mikey, you should write an article for our Network magazine, I know the editor would be interested in you contributing’.  Now, I’m not in favour of being called ‘Mikey’, but Liz always gets away with it. Regardless, that was the start of Research Reviews with Network.

It is important that I pay homage to that humble beginning as, like all good things, it must come to an end… or must it? This may be the last Research Review that will appear in the magazine format, but this prehistoric man is moving with the times, and will continue publishing the Research Reviews through Network online. To Liz, I thank you for initiating this journey and making it possible; to the Network magazine team, especially Oli our editor and Jack the primary designer, you make us look damn good. I thank you all for your patience and support, which I continue to enjoy. My Research Review colleague and friend Dr Joe Walsh and I are excited to keep Network’s fitness professional readership abreast of some of the more interesting and relevant developments in the world of exercise-related research. Which brings us, neatly, to this issue’s review.

Introduction: Early to bed, early to rise gets Mike the best waves in the morning. It’s no easy feat getting up in the dark in order to be in the surf line-up by sunrise, so you might say I rely upon go-go juice, java, jitter juice, morning jolt, cupped lightning. Call it what you want, it’s a cup of coffee with the all-important caffeine load that gets me going …and keeps me going with an afternoon kick when I’m fading and need a brain boost (yes, caffeine has been shown to improve cognitive performance).  

I’ve been in Australia long enough to know the so-called coffee I was drinking in the US was, to be polite, an evil beverage. When I came to the land of Oz I was enlightened with good, make that very good, coffee. Regardless, whether it tasted absolutely putrid or like the nectar of the gods, both had the all-important caffeine ingredient, which was a key factor when I was lifting weights, as well as when I needed to become functional early in the morning for a surf (or work). Caffeine has easy passage to all biological membranes after it has been consumed, with its peak effectiveness occurring from 30 minutes to two hours after consumption. This brings us to this Research Review, in which Dr Guest and her colleagues from the Faculty of Medicine at the University of Toronto published an excellent position stand on caffeine and exercise performance.

Caffeine is one of the most widely consumed natural stimulants from the methylxanthine class (i.e. it has stimulatory effects) which are found in plants.  In western countries, approximately 90% of adults consume caffeine on a daily basis, with consumption averaging approximately 200mg per day. Then, of course, there’s my colleague, Dr Luke Del Vecchio, a researcher extraordinaire in masters athletes and combat athletes, who is always above average for everything he does, so it’s a daily quadruple shot with 300mg of caffeine for him. I am truly amazed that he can drink such strong coffee. And this is coming from the guy who got an ablation on his heart last year and fears strong coffee. Luke attributes his tolerance to the Italian gene theory and habitual high caffeine ingestion levels.

Dr Guest et al. remind us that, today, caffeine is available in numerous products aside from coffee, including tea, cocoa, energy drinks, pre-workout supplements, chewing gum, energy gels, aerosols and a number of food products. Regardless of the form in which you prefer to consume your caffeine, both health (weight loss as well as lowered risk of type 2 diabetes mellitus, Alzheimer’s and Parkinson’s diseases, liver disease, depression and certain types of cancer) and performance benefits have been well documented in the scientific literature. It is the performance benefits that Dr Guest has focused her position stand on.

With regard to performance benefits, let’s put this into perspective at the Olympic level.  Researchers have shown that a less than 1% change in average running speed is enough to influence the medal results at Olympic endurance events from 45 seconds to 8 minutes in duration.  Caffeine has been shown by a number of studies to improve endurance performance by 2-4%, with a dose of 3 to 6 milligrams per kilogram of body weight. Therefore, we see cyclists, runners, cross-country skiers and swimmers utilising caffeine to boost performance. It is reported that approximately 75% of elite athletes used caffeine prior to or during competition. To quantify this benefit, a recent meta-analysis (in which study authors take the findings from a number of related studies) found the performance outputs of the caffeine-consuming study subjects to be approximately 16% greater than those of the placebo group subjects not taking caffeine (but thinking that they were). This is a substantial increase.

With regard to the effect of caffeine on strength, the authors report the most common dose of caffeine was 3 to 6 milligrams per kilogram of bodyweight, taken either in pills or capsules 30 to 90 minutes before strength training exercises. The authors report increases from 2-7% for muscular strength and similar (6-7%) for muscular endurance. They then then go on to list sports-specific improvements.

The authors also address a very important aspect of using caffeine to improve performance: interindividual variations in the response. They conclude that 50% of participants improved their overall performance, whilst the same percentage did not. Additionally, there are a number of deleterious effects associated with caffeine consumption. For example, some individuals, especially those with habitually low caffeine intake, may experience feelings of anxiety from its usage. Also, caffeine ingestion may hinder sleep quality, which is critical to athletic training, performance and recovery.  This may be mitigated by timing the ingestion of the caffeine.

The authors also review studies specific to the mode of caffeine ingestion (i.e. chewing gum, caffeine mouth rinsing, nasal spray/inspired powders, bars and gels) which is very interesting.

Pros: This is a very comprehensive article reviewing caffeine and exercise performance. Fitness enthusiasts using caffeine to enhance training or performance should give this position stand a read (available free online) as it will guide its use and expectations in performance outcomes.

The authors do well to also bring up the side-effects associated with caffeine consumption. These include tachycardia (racing heart rate), heart palpitations, anxiety, headaches, insomnia, hindered sleep quality, risk of heat-related illnesses if used in higher temperature environments, especially if hydration status is poor, and others. These side effects seem to increase with the dose ingested. It should be remembered that caffeine is widely used around the world and generally thought to be safe in moderate amounts, but it is a psychostimulant and can cause toxicity and even death (e.g. myocardial infarction) if consumed in high enough quantities (Willson, 2018).  If used, it should be used cautiously.

Cons: None.

Personal story here. As alluded to, I used to consume 2 ‘big gulps’ (~ 1.2 litres) of coffee religiously before every weights training session. Eventually, my stomach couldn’t take the acidity. A Scandinavian friend who threw the hammer on the track team told me he used caffeine tablets.  So, a visit to the local chemists and voila, now I’m good to go. A word to the wise, however: the first time I took the tablets my stomach turned and I was nauseous to say the least, so if you are going to try caffeine in this form, start low and go slow.

REFERENCES

• Guest et al., (2021). International Society of Sports Nutrition position stand: caffeine and exercise performance. Journal International Society of Sports Nutrition. 18(1): 1-37.
• Willson, C. (2018). The clinical toxicology of caffeine: A review and case study. Toxicology reports, 5, 1140-1152.

Assoc Prof Mike Climstein, PhD FASMF FACSM FAAESS AEP

Dr Climstein is one of Australia’s leading Accredited Exercise Physiologists. He is a faculty member in Clinical Exercise Physiology, Sport & Exercise Science at Southern Cross University (Gold Coast). [email protected]

Dr Joe Walsh, PhD

Joe has worked in a number of large international research teams with study findings presented around the world. In addition to working in the university sector, he is a director of Sport Science Institute. sportscienceinstitute.com

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