International Journal of Sport Nutrition and Exercise Metabolism, 2013, 23, 624 -628
© 2013 Human Kinetics, Inc.
www.IJSNEM-Journal.com
ORIGINAL RESEARCH
Perceptual Characteristics of Nutritional Supplements
Determine the Expected Effectiveness in Boosting
Strength, Endurance, and Concentration Performances
Attila Szabo, Márk Bérdi, Ferenc Köteles, and György Bárdos
The aim of this work was to examine the link between the physical-perceptual characteristics of nutritional
supplements and their expected effectiveness in enhancing sport performance. Participants (n = 267) ranked
nine images of fictive nutritional supplements, varying in shape, color, and route of administration (e.g., pill,
powder, lotion, etc.), in ranked- order of expected effectiveness. They performed the task three times, 1)
for strength, 2) endurance, and 3) for concentration. Results have revealed that the perceived effectiveness
of the supplements was statistically significantly different for the three types of performances (p < .001).
A significant interpersonal variability was observed in the ranking-order of the supplements. The findings
reveal that perceptual characteristics of ‘believed to be nutritional supplements’, aimed at sport performance
enhancement, influence their perceived effectiveness. Future inquiries in sport nutrition should examine the
relationship between expected and experienced effectiveness of various nutritional supplements in enhancing
sport performance.
Keywords: belief, baseline, expectancy, placebo, subjective
Chemical and behavioral performance enhancement
occurs in several life-areas. The effects could be attributed to active ingredients and/or interventions, or to the
placebo phenomenon. Behind placebo effects, usually
two partially overlapping psychological mechanisms
were mentioned: changes directly attributable to positive
expectations (or expectancies) and conditioned responses
(Kirsch, 1997; Kirsch & Sapirstein, 1998;. StewartWilliams & Podd, 2004). Moreover, negative expectations
and learned reactions could modify, in some cases even
completely reverse the effects of active drugs (Benedetti,
2008; Benedetti, Lanotte, Lopiano, & Colloca, 2007).
Behind suggestions and personal experiences,
placebo reactions could also be triggered by perceptual
properties of the agents, like shape, size, and/or color.
Warm colors (red, orange and yellow usually evoke
stimulative expectations, whereas cold colors (blue and
green) and white are connected to sedative-tranquillizing
effects in people’s mind (de Craen, Roos, de Vries &
Kleijnen, 1996; Köteles, Komsa & Bárdos, 2009). In a
number of situations, these expectations may manifest
themselves as actually experienced symptoms (Köteles
& Bárdos, 2011).
Placebo-reaction may also occur in nonmedical
contexts. For example, a literature review and a recent
meta-analysis have revealed that the placebo phenomenon could play a noteworthy role in the enhancement
The authors are with the Institute for Health Promotion and
Sport Sciences, Eötvös Loránd University, Budapest, Hungary.
624
of sport performance (Beedie & Foad, 2009; Bérdi,
Köteles, Szabo, & Bárdos, 2011). Although nonspecific
characteristics (e.g., features that are not connected to
biochemically active substances) of nutritional supplements may contribute to the placebo-reaction, no empirical research was conducted to date in this area (Bérdi
et al., 2011; Trojian & Beedie, 2008). Idiosyncrasy in
personal beliefs in relation to the perceptual properties
of the agents, associated with different types of performance, begs for a multilevel approach in studying the
effects of nutritional supplements in sports. The aim
of the current research was to examine: 1) the relationship between the physical / perceptual characteristics
of nine unnamed (fictive) nutritional supplements and
their perceived effectiveness in enhancing three types of
performance in sport: strength, endurance, and concentration, 2) the interindividual consistency in the expected
effectiveness of the presented supplements, and 3) the
link between expected effectiveness and past experience
with a resembling agent.
Materials and Method
The study was approved by the University’s Research
Ethics Board in Psychology and Health Sciences, and it
was conducted in accord with both national and international guidelines for research with human participants
(American Psychological Association, 2010). Regular
pysical activity and/or sport-participation in the past
12 months was a criteria for participation in the study.
Perceptual Characteristics and Effectiveness 625
Therefore, physically active undergraduates were called
for volunteering in the inquiry. The emerging sample (n
= 267, 95 men; 172 women, mean age = 20.0 yrs, SD =
1.7 yrs), reported nearly nine hours of physical activity
per week (mean = 8.93 hr, SD = 5.0, MDN = 8.0 hr), had
a similar cultural background, and gave consent to participation in the investigation. Their task was to place in
rank-order, on the basis of expected effectiveness—ranging from the most- to the least-effective—nine images
of unbranded (imaginary) nutritional supplements in
sport performance enhancement including green and red
drinks, white and red pills, white powder, white caplet,
energy bar, green gel, and white lotion. The nine fictive
agents were selected as unnamed alternatives, resembling
in perceptual characteristics, to the most common legally
(nonprescription based) available, “over the counter”
nutritional supplements in the region. The images were
presented simultaneously to the participants using identical neutral plain color background. Respondents were
asked not to associate the supplements with any specific
commercially known products and to pay attention only to
the perceptual characteristics of supplements. They also
had to indicate whether they have used a resembling (in
color and route of administration) supplement in the past.
A total of three rankings were performed, in counterbalanced order, separately for: 1) strength, 2) endurance, and
3) concentration. No time restriction was imposed in the
course of the study for the performance of the rankings.
Participants did not consult or interact with anybody
during the test session.
Data Analysis
The data gathered from the participants were inputted,
and then verified for accuracy, in Excel files. Subsequently, these data files were imported into the SPSS
statistical software (version 19) for statistical analyses.
Kendall’s W tests were performed for data on endurance,
strength, and concentration. This test is an extension of
the Friedman Test (c2) that simultaneously reveals the
results for the concordance (W, or the Kendall’s Coefficient of Concordance) in ranking the various substances.
To test the association between the perceived effectiveness of the supplements and past experience with a similar
substance, Spearman’s rho correlations were computed.
For testing between-gender differences in past experience
with similar (resembling to the rated) agents, one-way
analysis of variance (ANOVA was used).
Results
A total of 93.6% of the participants have self-reported
using in the past one or more supplements with perceptual
characteristics resembling those presented in the current
work. The means and standard deviations (in brackets)
were as follows: 2.1 (1.5) for endurance, 1.8 (1.3) for
strength and 1.7 (1.2) for concentration. No statistically
significant differences were disclosed in these measures
between men and women.
Friedman’s χ2 was statistically significant in all three
ratings (endurance χ 2 = 83.24, p < .001; strength χ2 =
151.96, p < .001; concentration χ2 = 235.12, p < .001;
see Figure 1). Post hoc tests obtained on these results
are summarized in Table 1). However, the Kendall’s W
values were small in all three instances (endurance=.04,
strength=.07, and concentration=.11), showing no agreement and, therefore, large interpersonal variability, in
the order of perceived effectiveness of the supplements.
Further, nine Friedman tests (one for each fictive
agent) were used with Bonferroni corrections to test the
statistical differences in the expectancy of effectiveness
among the three performances. These results revealed
that statistically significant between-performance type
differences (p < .001) have emerged in the case of white
lotion, white powder, green gel, and energy bar (Figure
1). The expected effectiveness of the other five perceptual
characteristics did not differ statistically significantly
among the three types of performances.
Finally, two correlational analyses yielded no significant results for endurance (rho = .03) and strength
(rho = -.13). However, a statistically significant correlation was obtained between the perceptual characteristics
and past experience with similar form of supplement for
concentration (rho = .96, p < .001).
Discussion
The findings reveal that images of unnamed nutritional
supplements with different physical characteristics are
perceived as having different effectiveness in enhancing
three types of performances: strength, endurance, and
concentration. For endurance, the green and red drinks,
red pill, white powder and white capsule were perceived
by the majority as most effective in enhancing performance, while the white lotion and the green gel were
perceived as least effective. The latter two could be seen
as generally pain relievers, rather than energy sources for
endurance. For strength performance, seven substances
with different visual-perceptual properties fared equally
well against white lotion and green gel, again likely for
the same reason as for endurance. For concentration, the
green drink and the energy bar were ranked superior to
the “white stuff” including white lotion, white powder,
white capsule, and white pill. The finding supports recent
results that color has a major influence on the subjective
perception of effectiveness and resulting action of various substances (Köteles et al., 2009). From a practical
point of view, these results suggest that the color and
the route of administration of nutritional supplements
influence the expected effectiveness, and hence the preference, of agents taken for different types of performance
enhancements in sport. Gels and lotions may be the least
attractive choices for enhancing endurance, strength, and
concentration.
Ratings of expected effectiveness of five out of the
nine supplements (i.e., green drink, red pill, red drink,
white capsule, and white pill) did not differ among the
three performances. The finding suggests that these agents
626
*
White pill
*
*
*
*
*
*
*
*
*
*
*
*
*
C
*
E
*
S
Red Pill
*
*
C
*
E
*
S
*
*
*
C
White Powder
Note. Statistically significant differences (p <.05) between the rows and columns are indicated with a star.
*
Energy bar
*
White capsule
*
*
Red drink
*
*
Green gel
*
*
*
*
White powder
*
*
*
Red pill
White lotion
Green drink
S
E
C
E
S
White Lotion
Green Drink
*
*
*
E
*
*
*
*
S
*
*
*
*
C
Green Gel
E
S
C
Red Drink
E
S
*
C
White Capsule
E
S
*
C
Energy Bar
E
S
C
White Pill
Table 1 Complementing Figure 1, the Table Shows the Results of the Post Hoc Pairwise Comparisons of the Perceived/Rated Potencies
of Nine Substances in Enhancing Endurance (E), Strength (S), and Concentration (C).
Perceptual Characteristics and Effectiveness 627
Figure 1 — Rating obtained for the effectiveness of nine substances in enhancing endurance, strength, and concentration. Betweenperformance differences in the rated effectiveness of an agent is marked with the level of the statistical probability where relevant.
may fair equally well in being selected for enhancing
three different types of performance in sport. However,
rated as least effective, the white lotion and green gel, as
well as the white powder and energy bar were expected
to have different effects on the three performances studied. Effectiveness ratings indicate that the white lotion
and green gel were thought to be primarily effective for
endurance, whereas the white powder was thought to be
superior for enhancing endurance and strength, and the
energy bar for concentration.
The low correlation between perceived effectiveness
of the presented agents and the past experience with a
resembling supplement obtained for endurance- and
strength-enhancement in contrast to the high correlation with concentration, affords only a hypothetical
explanation. It is likely that few students have already
used nutritional supplements for enhancing strength and
endurance. However, the relationship between perceived
effectiveness of the agents and past experience with a
similar substance was very strong for concentration. A
likely explanation is that while studying for exams many
students may resort to certain supplements for enhancing
concentration, which could be the source of the high correlation between perceived effectiveness of the agent and
past experience with a resembling supplement.
The ranking agreement was low between the participants, which could be ascribed to diverse subjective
beliefs and experiences. Information and experience
determine to a large extent the placebo or nocebo effects
manifested by various individuals (Stewart-Williams
& Podd, 2004). These findings may present a dilemma
for research using a quantitative-statistical approach. A
plausible solution in future research may be to recruit
representative samples of the general population and then
assess their preexisting beliefs concerning the effectiveness of a given agent. Subsequently, the examination of a
treatment effect should somehow consider (i.e., as covariate) the past beliefs about the effectiveness of a given
agent to determine the actual, or net, effect of the tested
substance. Based on the current results, it is possible that
observed efficacies would differ between “responders”
(those who believe in the effectiveness of the agent before
consumption) and “non-responders” (those who are
skeptical or distrust the effectiveness of the agent before
consumption). Unfortunately, net treatment effects were
not gauged in this study, because the agents were fictive
and only the effects of perceptual characteristics—of
imaginary supplements—were examined in addressing
the main scope of the research.
Limitations of the Study
The current study has certain limitations that ought to be
considered in future research. First, by using a rankingorder assessment instead of a rating scale, a ‘forcedchoice’ method was employed. This could yield different
results from assessing expectations of effectiveness on a
Likert scale on which two or more perceptually different
agents may be rated as equal in the perceived effectiveness. Future studies should also examine the perceived
absolute effectiveness of unbranded products varying
in shape and color. Second, the undergraduate sample
studied here, in spite of reporting nearly nine hours of
regular physical activity per week, may not be fully
628 Szabo et al.
representative of the elite athletic population competing at
high leveles or the typical “sport-supplement consumers”
who are involved in exaggerated hours of training, and
who are under some pressure for achievement. Finally,
the nine unnamed / fictive agents, with specific perceptual characteristics, may not represent the full spectrum
of freely available supplements in various sociocultural
environments. It is highly recommended that prospective
studies, pursuing this line of inquiry, also use real or
known (branded) supplements to establish “net effects”
beyond the perceived effectiveness.
Conclusions
Some agents (green and red drinks, red and white pills,
and white capsule) appear to be perceived as equally
effective for enhancing endurance, strength, and concentration. Others (white lotion and powder, green gel, and
energy bar) are perceived as having different effects on the
studied performances. This information shows that color
and form of a nutritional supplement affect its expected
effectiveness and, therefore, possibly the choice of the
agent. Accordingly, unbranded products with color and
form bearing the highest expectancy may be preferred in
selection and/or consumption of nutritional supplements
for various aspects of sport performance. Interindividual
ratings and, therefore, expected efficacies vary to a great
extent. Research on nutritional supplements aimed at
enhancing sporting performances should take into consideration the initial expectancy—developed on the basis
of knowledge or media-spread information and/or past
experience—associated with the studied supplement.
Acknowledgments
The Project is supported by the European Union and co-financed
by the European Social Fund (grant agreement no. TAMOP
4.2.1/B-09/1/KMR-2010-0003). The authors are grateful to
the anonymous reviewers whose constructive comments have
helped in substantially improving the manuscript.
Authors’ Note on Contribution: AS participated in the design,
statistical analysis, and manuscript preparation; MB and KF
participated in the design, data collection, data reduction, and
manuscript preparation; GB served as the principal investigator and contributed to study design, data collection, as well
as manuscript preparation. All authors read and approved the
revised manuscript.
This research was supported by the Hungarian National Scientific Research Fund (OTKA K 76880, K 109549) and by the
János Bolyai Research Scholarship of the Hungarian Academy
of Sciences (for F. Köteles).
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