Written by Damien Cox – Accredited Practising Dietitian


Caffeine can be found in many ways, coffee and tea, soft drink, tablets, powder, in food and in chewing gum. But what effect does it have on the human body and how can it effect exercise? Can it improve performance and give an extra boost when needed in the gym, or will it cause anxiety, and could it potentially hinder performance? Let’s take a deep dive into caffeine and what it’s all about.


Caffeine is one of the most studies supplements in the world and is believed to be the most frequently consumed psychostimulant worldwide [1,2]. It is contained in more than sixty plants which is extracted and mainly made into coffee [1]. Ironically coffee is the most consumed beverage in the world with 10.12 million bags sold in July 2022 alone [3].  The first ever text mentioning coffee as medication dates all the way back to 1025! [1]. Fast forward to 1903 psychologists and colleagues William Rivers and Harald Webber started looking at the effects on caffeine and sport performance [4]. Research continued through the 1900’s when a serious of studies were conducted in 1970 where the effects on caffeine and exercise metabolism and sport performance sparked a generation of research [4].


So what does caffeine actually do and how does it affect exercise performance?


After ingesting caffeine, it blocks adenosine receptors in Central Nervous System (CNS), increasing alertness and decreasing perceived exertion in exercise [2]. In some conditions caffeine also preserves muscle glycogen by utilising fatty acids in the bloodstream and energy use [2]. Caffeine also increases the release of calcium ions enhancing contraction power in muscle fibres [2,5]. After consumption caffeine peaks in the blood stream at with the time ranging from 30-120 minutes, however the most common and recommended timing of taking caffeine pre-exercise is 60 minutes [4].

Caffeine has been found to be most effective and beneficial during times or sports where there is an accumulation of fatigue ie exercise over long durations [4]. However, this does not limit caffeine and its effect on performance to just these sports. It has been shown to enhance performance through muscular endurance, movement velocity, and muscular strength, sprinting jumping and throwing performance, as well as a wide range of aerobic and anaerobic sport-specific actions [2,4].


As mentioned before caffeine comes in many different shapes and sizes. Depending on its form will depend on the amount of caffeine contained within the product.

Here are a few examples of the amount of caffeine in products [6]:


Item (per 100ml)

Total Caffeine (mg)





Soft drink


Energy drink


Caffeine tablet



The recommended dose for caffeine increasing performance is in doses of 3-6mg/kg of body weight. Levels above this (9mg/kg) have shown to increase performance however increases the likelihood of negative side effects such as gastrointestinal upset, nervousness, mental confusion, and the inability to focus.


When used correctly caffeine can be a great supplement when wanting to increase sport performance. Finding products which clearly state the amounts can be a useful tool when calculating how much caffeine is needed to consume. If you’re unsure about caffeine or how to use it in conjunction with exercise talk to a nutrition professional about how it can be best suited to your lifestyle.


Reference List:

  1. doi: 2174/1570159X13666141210215655
  2. https://doi.org/10.3389/fspor.2020.574854
  3. https://www.ico.org
  4. https://doi.org/10.1186/s12970-020-00383-4
  5. https://doi.org/10.1016/j.neubiorev.2016.09.001
  6. doi: 2174/1570159X13666141210215655


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