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Bliss & Depperschmidt (2011)1 ran an exploratory study into the use and perceived effects of energy drink consumption with regards to collegiate flight students. This article summarises and reanalyses the results to provide the reader with more useable findings.

Use of energy drinks

Out of the background questions in the study, 3 interesting summaries can be drawn:

  1. 60% of participants were regular users of energy drinks.
  2. 66% of these regular users felt that they would experience side-effects if they consume more than 1 energy drink.
  3. All of the regular users had flown an aircraft they same day as consuming an energy drink.

Note: "side-effects" was the term used in the original study. It did not ask participants whether they felt it was positive or detrimental.

Effects of energy drinks

Bliss & Depperschmidt (2011)1 obtained participants' opinions towards 10 Likert-scale statements. To understand their findings, these have been categorised into physical effects (effecting the way the body operates), psychological effects (effecting the way the mind operates), and practical effects (effecting the ability to pilot an aircraft). The categorised statements are as follows:

Physical effect probes

  • Jolt and crash (high/low energy) episodes are typical after consumption of energy drinks
  • Headaches are common after consuming energy drinks
  • Heart palpitations (pounding or racing) are common after consuming energy drinks

Psychological effect probes

  • Energy drinks have an effect on short term memory
  • Chronic use of energy drinks can lead to other use of stimulants
  • The consumption of energy drinks can be associated with risky or behaviour problems

Practical effect probes

  • Energy drinks have an effect on collegiate flight students’ ability to pilot an aircraft
  • Collegiate flight students should consume an energy drink the same day they operate an aircraft

Note: 2 probes were omitted as one was considered trivial, and the other was double-barreled. Any statements that were written in the negative tense in the original study have been converted into positive tense and the results reversed.


The Likert-scale used in the study had four levels of opinion: strongly agree, agree, disagree, and strongly disagree. These can be assigned numerical ordinal values as so: strongly agree = 4, agree = 3, disagree = 2, and strongly disagree =1. Each category is shown with its frequency of each response type and the overall mean opinion with standard deviation in the table below.

Table 1: Categories by frequency of responses, mean, and standard deviation
Frequency of responses Statistics
Strongly Agree (4) Agree (3) Disagree (2) Strongly Disagree (1) Mean Standard Deviation
Physical effects 4 40 41 5 2.48 0.67
Psychological effects 3 28 47 12 2.24 0.72
Practical effects 5 42 11 2 2.83 0.62
Note: There are less respondents for practical effects because there were only 2 probes categorised, not 3.

Effect size

The mean and standard deviation can now be used to compare the effect of energy drinks across categories. The table below compares the categories using effect size.

Table 2: Categories by effect size
Comparison Difference between means Effect size Interpretation
Psychological vs. Physical 0.24 0.36 Small
Physical vs. Practical 0.35 0.52 Medium
Practical vs. Psychological 0.59 0.88 Large


From this analysis it is possible to conclude that energy drinks are being used by flight students the same day they pilot an aircraft. The pilot students perceive that they experience side-effects of energy drink consumption, but we cannot conclude whether they are positive or detrimental. By categorising the probes used in Bliss & Depperschmidt's (2011)1 exploratory study and comparing the categories by effect size it was possible to determine that practical effects were perceived to be the biggest effect of energy drinks, followed by physical, and then psychological effects. This analysis is based on perceptions of flight students, not concrete variables. Accordingly, these findings can only be used to guide further research into the effect of energy drinks in the aviation context.


Research approach

Exploratory research into the perceived effects of energy drinks on collegiate flight students.


30 collegiate flight students from Oklahoma State University. Convenience sampling was used. The sample displayed a good range of year levels and total flight times.

Data analysis

Descriptive statistics. Central tendency was measured using means for each category. While this is not common for ordinal level data, it allows standard deviation to be calculated. The mean for each category was calculated by multiplying the frequency of each response type by its ordinal value, adding each response type for that category, and then dividing by the number of respondents. It was possible to then compare the categories on effect size by dividing the difference between means by the average standard deviation.

Generalisation potential

The sample used was only collegiate flight students. Therefore findings can only be generalised to other collegiate flight students. This being said, the study does give direction for future research on the effects of energy drink consumption because it identifies what areas student pilot's believe are effected by their use.

1. Bliss, T.J., & Depperschmidt, C.L. (2011). Energy drink consumption and its effects on student pilots: Perceptions of collegiate flight students. Collegiate Aviation Review, 21(2), pages 1 - 12.

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