BiologyHealth Sciences

How Do Drinks Affect Reaction Time?


In modern society, professional athletes, especially sprinters often use illegal steroids or drinks that affect their reaction times to maximize their performance. For example, the Jamaican sprinter Nesta Carter has been caught out in the reanalysis of his blood and urine samples, which found that he used the illegal substance methylhexaneamine to increase his performance.

Reaction time is essentially defined as the time taken for a stimulus to be picked up by the receptors in the body and the response to be carried out by the central nervous system as a result of the stimulus. Electrical impulses travel from the sensory neurones to the motor neurones. These signals travel through junctions called synapses between the ends of neurones by transmitting chemicals and diffusing through the gaps. This however, may cause some to be confused with reflexes. Reflexes, unlike reactions, are involuntary actions used to protect the body. They are much quicker than reactions as the electrical impulse doesn’t go through the central nervous system, but goes straight to the effector muscles from the receptors.

The principle of the experiment was to examine why certain drinks affected reaction time more than others, and what their particular effects are. With our particular interests in sports, we wanted to incorporate our passion into the fields of science.


To find out which drink is the most effective in reducing reaction time, and why.

Experiment #1

The experiment involved drinking 200ml of eight different common drinks: Powerade, Coca-Cola, Ribena, Orange juice, Coffee, Protein drink (Whey), Lucozade and Red Bull.

We tested this by measuring our reaction times using a reaction time data logger which was connected to a computer after having consumed 200ml of the drink, with a time interval between 0 minutes to 10 minutes. The reaction time data logger involved pressing a button as soon as the symbol on a computer screen turned from white to yellow, and the time taken between the colour turning yellow and you pressing the button determines your reaction time. We repeated this procedure 10 times, giving 10 readings and then averaged to give the mean result, as to increase the reliability of the results. The colour change was controlled by a different person, ensuring that the subject could not predict the next colour change. As I mentioned earlier, the repetition was necessary for reliability and we averaged the readings to evaluate whether the results correlated to the mean. This also allowed us to identify an possible anomalies. Hence, it is plausible to conclude that the results are reliable if they are more or less similar to each other.

Results can vary for each subject so we measured a control for each person by conducting the experiment having only just drunk water and no other liquids beforehand.

Experiment #2

To further evaluate and prove the effects of the drinks on reaction times, we used a second experiment which involved one person dropping a 30cm ruler at eye level and the subject catching it as fast as possible. We made sure that the 0cm mark was at the bottom and that the 30cm mark was at the top. We also ensured the subject to place his index finger and thumb parallel across the 0cm mark on the ruler, and that the top of the subject’s thumb was in line with the 0cm line on the ruler. The subject would then catch the ruler with his index finger and thumb only. We measured the length at which the subject caught the ruler, and repeated this procedure three times to increase the reliability. Then, by calculating the mean of the three results, we concluded with a more reliable outcome.

Here, we also conducted the experiment with each person only having drank water and no other liquids beforehand as to measure the control.

Validity of the Experiments

To keep the experiment fair, a number of variables were kept constant.

Firstly, we conducted the experiments using only one drink every week so that the recordings would not be affected by any other liquids. Secondly, we carefully regulated the volume of the beverages consumed (200ml) by pouring it out into cups using a measuring cylinder and also measuring from the meniscus. To obtain a wider array of data points, we performed the experiment on three subjects, rather than just one. Lastly, we varied the time periods for each experiment. This would then allow us to not only calculate whether the drinks solely affected reaction times but also the time it took for each drink to take effect.

Water (control) 0.266s/14.2cm


Water (control) 0.277s/13.3cm


Water (control) 0.272s/13.1cm

Orange Juice

Hypothesis: Due to the amount of sugar in this drink, we predicted this drink to allow a faster reaction time but not for a long time.

Orange juice Immediately 5 mins after 10 mins after
Trevor 0.273s 0.261s 0.275s
Jebin 0.256s 0.249s 0.255s
Jack 0.290s 0.267s 0.285S


Conclusion: Our hypothesis matched the results. In fact, all the results after 5 minutes showed that there was a quicker reaction time but all the results after 10 minutes illustrated how the reaction times slowed down towards the control.



1:4 ratio; Ribena to water

Ribena Immediately 5 mins after 10 mins after
Trevor 0.288s 0.286s 0.285s
Jebin 0.282s 0.269s 0.279s
Jack 0.292s 0.272s 0.284s


Coca Cola Immediately 5 mins after 10 mins after
Trevor 0.271s 0.257s 0.230s
Jebin 0.283s 0.261s 0.247s
Jack 0.297s 0.281s 0.264s


Powerade Immediately 5 mins after 10 mins after
Trevor 0.275s 0.277s 0.269s
Jebin 0.267s 0.251s 0.247s
Jack 0.269s 0.261s 0.262s


Coffee Immediately 5 mins after 10 mins after
Trevor 0.244s 0.229s 0.222s
Jebin 0.261s 0.230s 0.219s
Jack 0.252s 0.233s 0.219s


Protein drink (Whey) Immediately 5 mins after 10 mins after
Trevor 0.269s 0.270s 0.276s
Jebin 0.265s 0.271s 0.272s
Jack 0.272s 0.278s 0.280s


Lucozade Immediately 5 mins after 10 mins after
Trevor 0.261s 0.247s 0.245s
Jebin 0.267s 0.254s 0.255s
Jack 0.280s 0.274s 0.273s


Red Bull Immediately 5 mins after 10 mins after
Trevor 0.272s 0.267s 0.260s
Jebin 0.275s 0.268s 0.259s
Jack 0.284s 0.281s 0.279s


Limitations of the experiments:

The main flaw in our project was the number of participants. A larger number of subjects would mean that a more reliable and concise result is obtained because it is possible to evaluate whether the results are close to the mean. The reason for the lack of candidates were due to the lengthy time commitment. Also, in the future, the use of female subjects could show that drinks affect reaction time in both sexes.

Another limitation would have been the meal before the experiment. A nutritious meal with plenty of water beforehand could slightly affect the reaction time but we tried to keep this factor to the minimum by leaving a four hour gap between the meal and the experiment for time to digest. The experiment took place over approximately 1.5 school terms.

What components in the drinks affect reaction time?

After having compared the nutritional values of all the drinks, it was discovered that the main three ingredients which differed significantly for each drink were the amounts of sugar (glucose), caffeine and protein.

Higher glucose levels in the drinks generally meant that a faster decision time was measured. This is due to an increased synthesis of acetylcholine which signifies a higher production of neurotransmitters in the brain and the body. In other words, acetylcholine is the chemical secreted by motor neurons that helps to move muscles, so, more acetylcholine ensures the quickest response.

Higher protein levels meant that a faster reaction time was measured. Branched chain amino acids and phenylalanine in plasma were significantly increased.

Higher caffeine levels meant that a faster reaction time was measured. Caffeine stimulates the production of adrenaline and in this way caffeine is able to block nerve cells in the brain from detecting adenosine. Adenosine greatly reduces and stabilizes nerve activity, therefore without this chemical, brain activity increases significantly. The effect of this causes the pituitary to release adrenaline which tenses up the muscles prepared for immediate action.


About the Author

Trevor is currently 17 and studying in the Kings School Canterbury. He is an aspiring medic who also takes an interest towards science, particularly biology, sports and fitness, and the general anatomy of the human body.

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