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Abstract

The placebo effect-a change attributable only to an individual's belief in the efficacy of a treatment-might provide a worthwhile improvement in physical performance. Although sports scientists account for placebo effects by blinding subjects to treatments, little research has sought to quantify and explain the effect itself. The present study explored the placebo effect in laboratory cycling performance using quantitative and qualitative methods. Six well-trained male cyclists undertook two baseline and three experimental 10-km time trials. Subjects were informed that in the experimental trials they would each receive a placebo, 4.5 mg.kg caffeine, and 9.0 mg.kg caffeine, randomly assigned. However, placebos were administered in all experimental conditions. Semistructured interviews were also conducted to explore subjects' experience of the effects of the capsules before and after revealing the deception. A likely trivial increase in mean power of 1.0% over baseline was associated with experimental trials (95% confidence limits, -1.4 to 3.6%), rising to a likely beneficial 2.2% increase in power associated with experimental trials in which subjects believed they had ingested caffeine (-0.8 to 5.4%). A dose-response relationship was evident in experimental trials, with subjects producing 1.4% less power than at baseline when they believed they had ingested a placebo (-4.6 to 1.9%), 1.3% more power than at baseline when they believed they had ingested 4.5 mg.kg caffeine (-1.4 to 4.1%), and 3.1% more power than at baseline when they believed they had ingested 9.0 mg.kg caffeine (-0.4 to 6.7%). All subjects reported caffeine-related symptoms. Quantitative and qualitative data suggest that placebo effects are associated with the administration of caffeine and that these effects may directly or indirectly enhance performance in well-trained cyclists.
Copyright @ 2006 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Psychobiology and Behavioral Strategies
Placebo Effects of Caffeine
on Cycling Performance
CHRISTOPHER J. BEEDIE, ELIZABETH M. STUART, DAMIAN A. COLEMAN, and ABIGAIL J. FOAD
Canterbury Christ Church University, Canterbury, UNITED KINGDOM
ABSTRACT
BEEDIE, C. J., E. M. STUART, D. A. COLEMAN, and A. J. FOAD. Placebo Effects of Caffeine on Cycling Performance. Med. Sci.
Sports Exerc., Vol. 38, No. 12, pp. 2159–2164, 2006. Purpose: The placebo effectVa change attributable only to an individual`s
belief in the efficacy of a treatmentVmight provide a worthwhile improvement in physical performance. Although sports scientists
account for placebo effects by blinding subjects to treatments, little research has sought to quantify and explain the effect itself. The
present study explored the placebo effect in laboratory cycling performance using quantitative and qualitative methods. Method: Six
well-trained male cyclists undertook two baseline and three experimental 10-km time trials. Subjects were informed that in the
experimental trials they would each receive a placebo, 4.5 mgIkg
j1
caffeine, and 9.0 mgIkg
j1
caffeine, randomly assigned. However,
placebos were administered in all experimental conditions. Semistructured interviews were also conducted to explore subjects`
experience of the effects of the capsules before and after revealing the deception. Results: A likely trivial increase in mean power of
1.0% over baseline was associated with experimental trials (95% confidence limits, j1.4 to 3.6%), rising to a likely beneficial 2.2%
increase in power associated with experimental trials in which subjects believed they had ingested caffeine (j0.8 to 5.4%). A dose–
response relationship was evident in experimental trials, with subjects producing 1.4% less power than at baseline when they believed
they had ingested a placebo (j4.6 to 1.9%), 1.3% more power than at baseline when they believed they had ingested 4.5 mgIkg
j1
caffeine (j1.4 to 4.1%), and 3.1% more power than at baseline when they believed they had ingested 9.0 mgIkg
j1
caffeine (j0.4 to
6.7%). All subjects reported caffeine-related symptoms. Conclusions: Quantitative and qualitative data suggest that placebo effects
are associated with the administration of caffeine and that these effects may directly or indirectly enhance performance in well-trained
cyclists. Key Words: EXPERIMENTAL DESIGNS, DECEPTIVE ADMINISTRATION, ERGOGENIC AIDS, BELIEF EFFECTS
The placebo effect is a favorable outcome arising
purely from the belief that one has received a
beneficial treatment (4). It could be argued that in
relation to sports performance and research, the placebo
effect is widely acknowledged but little understood. Cer-
tainly, in common with practice in disciplines such as
medicine and clinical psychology, sports scientists account
for the possibility of a placebo effect in intervention studies
by using a placebo control condition. However, despite
evidence elsewhere that the placebo effect impacts a wide
range of physiological, psychological, and behavioral varia-
bles (6), the placebo effect per se has received scant
attention in sports science research. The few studies that
have specifically addressed the placebo effect in sport
(2,4,8,13), despite collectively providing little systematic
information relating to its magnitude or mechanisms, do
suggest that placebo effects might be associated with several
nutritional and pharmacological interventions. For example,
Clark et al. (4) reported placebo effects associated with
carbohydrate supplementation in cycling performance. Sub-
jects were allocated to three groups and were advised that
the carbohydrate group would probably show the most
improvement in performance. However, half of the carbo-
hydrate group was randomized to receive the placebo, and
half of the placebo group was randomized to receive the
carbohydrate. Those in the third group were informed,
correctly, that there was a 50:50 chance that their drink
would contain carbohydrate. Results indicated a difference
in mean power between the told-carbohydrate and told-
placebo groups of 3.8% (95% confidence/likely limits/range
= 0.2 to 7.9%).
Clark and colleagues made several recommendations for
future placebo-effect research, including the use of crossover
designs and the exploration of factors that might account for
individual differences in placebo responsiveness. The aim of
the present study was twofold: first, to use a crossover design
to investigate whether athletes given a placebo under the
impression it was a performance-enhancing substance would
perform at a higher level than in control conditions, and
Address for correspondence: Dr. Christopher J. Beedie, Department of
Sport Science, Tourism, and Leisure, Canterbury Christ Church Univer-
sity, Canterbury, CT1 1QU, UK; E-mail: c.j.beedie@canterbury.ac.uk.
Submitted for publication November 2005.
Accepted for publication June 2006.
0195-9131/06/3812-2159/0
MEDICINE & SCIENCE IN SPORTS & EXERCISE
Ò
Copyright Ó2006 by the American College of Sports Medicine
DOI: 10.1249/01.mss.0000233805.56315.a9
2159
Copyright @ 2006 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
secondly, to ascertain how the athletes themselves attributed
any perceived or observed changes in performance.
METHOD
Subjects. Institutional ethics approval and written
informed consent from all subjects were obtained. Subjects
were well-trained competitive male cyclists (N=7,age=30
T11 yr, height = 180 T6.3 cm, weight = 75 T5.1 kg)
recruited from local cycling teams. Before the performance
trials, and with the aim of catalyzing or reinforcing beliefs
about caffeine, subjects were provided with literature
reviewing the findings of published research into caffeine
and cycling performance and detailing anecdotal evidence
regarding the use of caffeine among elite cyclists. The
efficacy of this manipulation was assessed in poststudy
interviews. Initial analyses of experimental performance
trials indicated that the power output of subject 4 varied by
up to 20% between adjacent trials. His data were removed
from further statistical analysis, but his interview responses
are of interest and are reported below.
Procedure. Subjects each performed two 10-km
habituation trials and one V
˙O
2max
test on the SRM cycle
ergometer (Ingenieurburo Schoberer, Julich, Germany).
The SRM was set up to exactly replicate the subjects`
habitual riding position. Subjects performed five maximal-
effort 10-km time trials (each preceded by a standardized,
progressive 20-min warm-up), in the order of one
prebaseline (control), three experimental, and one
postbaseline (control). Subjects were informed that they
would perform one experimental trial in each of three
conditions: placebo, 4.5 mgIkg
j1
caffeine (moderate dose),
and 9.0 mgIkg
j1
caffeine (high dose), on a randomly
assigned double-blind basis. However, a deceptive
administration protocol (14) was employed: an identical
placebo capsule was administered in each experimental
trial. No caffeine was administered during the study.
Measures were power, oxygen uptake, heart rate, and
blood lactate concentration, taken every 2 km at the thumb.
Each of the trials was separated by a 3- to 10-d gap, and
the subjects were asked to maintain their usual training
and diet during the study but to refrain from heavy training
for 24 h before each trial. They were also asked not to
consume any caffeine after 6:00 p.m. the night before
testing to control for the effects of caffeine already con-
sumed (14).
Subjects in caffeine research might engage in an active
search for symptoms to identify to which experimental
condition they have been allocated (15). Recent research
has suggested that physical activity masks several of the
expected cognitive effects of caffeine (7). Thus, to ensure
that the integrity of the experimental deception was
maintained, capsules were not administered until the
subject was seated on the ergometer and pedaling.
To limit the potential for subjects to employ any pacing
strategies based on performance in previous trials, the only
performance-related feedback available to them during
trials was the distance they had covered. Similarly, to
preclude the possibility that knowledge of performance
data would contaminate post hoc attributions (e.g., the
attribution of a random increase in power to caffeine
irrespective of any real perceptions of caffeine effects),
feedback of all performance data was withheld until the
completion of the study.
Post hoc measures. Questionnaires were adminis-
tered after each experimental trial. Items included ‘‘Which
conditionVplacebo, low-dose caffeine, or high-dose
caffeineVdo you think you completed today?’’ ‘‘To
what extent did the capsule effect your performance’’
and ‘‘Did you experience any side effects?’’ Subjects were
reminded at this stage that they would complete only one
trial per condition. Although subjects were given the
opportunity to revise allocation of trial to condition at the
end of the experimental phase of the study, none chose to
do so.
Analyses. Performances in baseline trials were
averaged to estimate changes in treatment trials. Changes
in log-transformed mean power, oxygen uptake, lactate,
and heart rate between trials were analyzed using one-way
repeated-measures ANOVA. Recently, Batterham and
Hopkins (3) proposed the use of magnitude-based
inference, whereby the smallest worthwhile effect is
identified and justified, confidence limits are interpreted
in relation to this effect, and probabilities that the true
effect is beneficial, trivial, and/or harmful are derived.
Data below are presented in accordance with these
suggestions. Paton and Hopkins (16) have suggested that
the smallest practically beneficial improvement in
performance for a road cyclist is that equivalent to an
approximately 1.5% increase in power output; conse-
quently, this value was adopted as the threshold level for
the interpretation of confidence intervals.
The experimental design relied on a deceptive adminis-
tration protocol. Ethical guidelines of the American
Psychological Association (1) and our institutional ethics
committee required that subjects be thoroughly debriefed at
the conclusion of the data collection. The debrief process
was incorporated into poststudy interviews carried out in
the week after the final performance tests. Two semi-
structured interview schedules were prepared. Schedule 1,
delivered before revealing the results and the deception,
included questions such as ‘‘Did you expect caffeine to
effect your performance?’’ ‘‘What symptoms did you
experience?’’ and ‘‘Do you think that the caffeine affected
your performance?’’ Schedule 2, delivered after the results
and the deception had been revealed, investigated subjects`
previous responses in light of their knowledge that they
had received no caffeine. Interviews were conducted by the
first and second authors with one subject at a time in a
private office. Each interview lasted between 60 and 100 min,
and each was tape recorded with the subject`s permission. All
interviews were transcribed, and data were analyzed using
inductive content analysis as demonstrated by Jackson (9).
However, the resulting analysis seemed overly complex and
raised several themes, for example ‘‘trust in experimenters’
and ‘‘future use of caffeine,’’ which went beyond the scope
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of the present study. Subsequently, we adopted a less
analytical approach by summarizing responses relevant to
placebo effects.
RESULTS
Mean values by condition for all measured variables are
presented in Table 1. Mean and standard deviations for
percentage differences in power over baseline, confidence
intervals, and likelihood of worthwhile effects are
presented in Table 2. Interpretation of confidence intervals
revealed a likely trivial difference in power between pre-
and postbaseline trials, suggesting no systematic learning
or training effects. Overall, there was no practically
beneficial difference in power between mean baseline and
mean experimental conditions, although a dose–response
relationship was evident, with the placebo condition being
associated with a mean decrease in power compared with
baseline, whereas possibly beneficial and likely beneficial
increases in power were associated with the moderate- and
high-dose caffeine conditions, respectively. The within-
subject coefficient of variation (CV) for log-transformed
power was calculated at 2.7%. No substantial difference
was evident between the CV for baseline and for experi-
mental conditions.
Interpretation of 95% confidence intervals indicated no
substantial differences between mean baseline and either
mean experimental or mean caffeine conditions for heart
rate, oxygen uptake, and blood lactate.
Interview data (N= 7) indicated that five subjects
(subjects 1, 2, 3, 4, and 6) attributed direct performance
effects to the capsules, subject 5 was unsure whether to
attribute performance effects to the capsules, and subject 7
reported no performance effects (note that interview data
for subject 4 is included despite his experimental data
being removed from statistical analyses above). Perfor-
mance data were consistent with the interview data of five
subjectsVfor example, subjects 2 and 6, whose experi-
mental and interview data both suggest that they experi-
enced a placebo effect, subject 4, whose interview and
performance data arguably suggested a negative placebo or
‘nocebo’’ effect, and subject 7, whose experimental and
interview data both suggest that he did not experience a
placebo effect. Interview responses suggested three spe-
cific areas of interest; expectation of caffeine effects,
perceived effects of caffeine on performance, and potential
mechanisms.
Expectation of caffeine effects. Four subjects
(subjects 1, 2, 3, and 4) indicated that they expected the
capsules to have a positive effect on their performance.
However, no clear relationship between belief in caffeine
and performance emerged. For example, subject 6, whose
performance data suggested that he experienced a
significant placebo response and who subsequently
indicated that he believed this to be the case, reported
very low a priori expectation of caffeine effects. Subject 4,
however, indicated that he was expecting caffeine ‘‘to have
a mega effect’’ and went on to describe how, on the basis
of symptoms experienced during what he believed was the
high-dose caffeine trial, he was unable to complete it,
stating ‘‘I felt terrible, that must have been the big dose of
caffeine.’’ It is possible that this poor performance may
have resulted from illness.
Effects on performance. Five subjects (subjects 1, 2,
3, 4, and 6) reported direct effects of caffeine on
performance. Subject 1 reported that during certain tests,
‘it got to the point at which on the previous test you really
[feel] the pain to the legs and you start to go down a bit, on
another test I got to that stage but then I lifted again,’’ and
‘you get a bit more aggressive you sort of pick up the rpm
again and you think to yourself, Fthis must be the
caffeine.`’ Subject 2 suggested, ‘‘when I thought I was
on the 9 mg of caffeine I went faster, I felt more on top of
it whereas all the other times I felt like I was having to dig
in just to keep the pedals turning over. I think I was
pushing a bigger gear than normal, I was able to push
harder with less pain.’’ Subject 6 suggested, ‘‘the first time
I had the tablet was definitely an improvement on the
[trial] before. I was surprised actually how different it felt,
whether that was [the tablets] or not I still obviously don`t
know, but certainly that first tablet I took I thought, Fwell,
this is a damn sight easier than it was last time.`’’ H e
suggested that during experimental trials, ‘‘it was easier to
put the effort in, there wasn`t any tiredness creeping in, I
was actually expecting to start feeling tired at a particular
point normally after about 10 min on the bike and it didn`t
so you think Foh great, well I`ll press a little bit harder and
I`ll go a little bit faster.`’’ Subject 7 suggested, ‘‘one
particular day when I turned up and did it I felt really
zippy, you pedal and you pedal hard and you`re out of
breath but you feel you can ride at that threshold and a
little bit higher,’’ but this subject also added, ‘‘whether it
was because of the caffeine, I don`t know.’’
Placebo mechanisms. Six subjects (all except
subject 7) suggested potential placebo-effect mechanisms.
TABLE 1. Means and standard deviations for power output, blood lactate, oxygen
uptake, and heart rate by condition (N= 6).
Power
(W)
Lactate
(mM)
V
˙O
2
(mLIkg
j1
Imin
j1
)
Heart Rate
(bpm)
Pre baseline 276.6 (39.1) 10.7 (1.5) 57.8 (9.0) 178.1 (10.1)
Placebo 274.3 (46.3) 10.5 (3.3) 60.2 (8.2) 169.2 (14.4)
4.5 mgIkg
j1
280.6 (37.1) 10.8 (2.5) 56.8 (11.0) 172.4 (13.9)
9.0 mgIkg
j1
285.9 (38.7) 11.3 (2.7) 57.8 (10.8) 171.4 (14.2)
Post baseline 278.9 (41.0) 10.7 (3.1) 58.0 (8.8) 172.4 (14.7)
Mean baseline 277.7 (42.3) 10.7 (2.3) 57.9 (8.8) 172.2 (12.2)
Mean experimental 280.3 (40.5) 10.9 (2.7) 58.3 (9.7) 171.0 (13.9)
Mean caffeine 283.2 (37.8) 11.0 (2.7) 58.8 (9.7) 171.94 (14.0)
TABLE 2. Mean and SD percentage differences in power over baseline, confidence
intervals, and practical significance of effects (N= 6).
Percent Change over
Mean Baseline (%) 95% CI
Percent Chance That
Effect is Beneficial
(Mean [SD]) (Lower to Upper) (Trivial/Harmful)
Mean experimental 1.0 (2.4) j1.4 to 3.6 34 (64/2)
Placebo j1.4 (3.1) j4.6 to 1.9 4 (51/46)
4.5 mgIkg
j1
1.3 (2.7) j1.4 to 4.1 45 (53/2)
9.0 mgIkg
j1
3.1 (3.4) j0.4 to 6.7 86 (13/1)
Mean caffeine 2.2 (3.0) j0.8 to 5.4 72 (26/1)
PLACEBO EFFECTS IN CYCLING PERFORMANCE Medicine & Science in Sports & Exercise
d
2161
Copyright @ 2006 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
These explanations fell into four broad categories: a) pain
reduction(sixsubjects)Vfor example, ‘‘the pain went
away,’’ ‘‘I don`t think there was so much pain,’’ ‘‘It`s not
that you feel it more or less you can just tolerate [pain] a bit
more,’’ ‘‘I was able to push harder with less pain,’’ and
‘[you can ride] without it hurting and that`s the difference’’;
b) belief–behavior relationships (four subjects)Vfor
example, ‘‘because you think that you`ve taken caffeine,
there must be something in the brain that might tell
you`ve taken something that`s gonna make you go better
so it does,’’ ‘‘there is this great big tablet and you think
Fthere must be a huge dose in there therefore this is
gonna do something really good`and perhaps just that
pure belief or hope that it was gonna do something did do
something,’’ and ‘‘you just believe that it`s gonna make
you stronger and you believe in it enough to actually
make you stronger, so you try to bring yourself up to the
level of the difference that it`s supposed to make, you
actually raise your game to try and match the tablet’’; c)
attentional changes (two subjects)Vfor example, ‘‘you`re
focusing on something else that`s helping you so it
actually takes your attention away from hurting so
much`’; and d) arousal changes (two subjects)Vfor
example, ‘‘it calms you because you know you are
getting something to help youII tend to ride better if
I`m more relaxed. In my jobVI`m a firemanVyou`ve
only got this air on the back and that`s all you`ve got.
When you go into a lighted [building], if you keep calm
as you can you use less air, so you`re more efficient if
you`re more calm.’
DISCUSSION
When subjects were administered a placebo capsule they
believed to be caffeine, they produced, on average,
substantially greater power than at baseline. Furthermore,
effects were stronger when subjects believed they had
ingested higher doses of caffeine. The coefficient of
variation for power was comparable with previous research
on elite cyclists (15) and lower than for several current lab-
based cycle performance tests (5), suggesting that the
observed effects are unlikely to be the results of random
biological or mechanical variations. Using recently pub-
lished criteria (16), we are able to state that the effects
observed are likely to be of practical benefit to a road
cyclist in competition. Furthermore, some of these effects
are similar in magnitude to those attributed to caffeine in
several published performance studies (19).
Subjects in the present study had a 67% expectation of
caffeine ingestion. Had we adopted a design that more
closely replicated real-life drug-administration protocols,
that is, a deceptive no-blind design in which subjects had a
100% expectation of caffeine administration, we might
have expected performance effects of greater magnitude.
Use of such a design might also have permitted us a greater
degree of confidence in stating that observed effects
resulted directly from the intervention (i.e., they were
placebo effects) and not from a process whereby a subject
simply felt good on one or more days and attributed those
feelings to the effects of ingested caffeine. We acknowl-
edge that the potential for subjects to attribute random
changes in performance to the ingestion of caffeine was a
limitation of the experimental design. However, a secon-
dary aim of the present study was to investigate the
mechanisms underlying subjects`attribution of trial to
condition, and therefore we aimed to leave subjects in
some doubt as to whether they had ingested caffeine in any
one trial. It was anticipated that subsequent interview data
might elucidate the mechanisms underlying subjects`
allocation of trial to condition. To a certain extent, this
approach was fruitful. For example, two subjects indicated
that because they believed they had already received
caffeine in the first and second experimental trials, they
had low or zero expectation of caffeine administration in
the third (subject 2 suggested, ‘‘maybe going into the final
day having had a really fast day and one relatively fast
makes you think Fhang on a second you can`t be given
caffeine again`’’). This finding suggests that subjects`
assumptions about what has or has not been administered
in previous trialsVplacebo or drugVmight influence
performance in subsequent trials.
Potential placebo mechanismsVfor example, whether
the placebo effect is manifest as a direct effect on
performance or whether a subject`s awareness of caffeine
symptoms leads to a revised pacing strategy and, thereby,
enhanced performanceVare of some significance to sports
performance research. In this respect, it is interesting that
ANOVA revealed no differences between baseline and
experimental conditions in any measured physiological
variables, which suggests that changes in performance may
not have been the result of deliberate changes in pace (this
finding, however, might also be a statistical anomaly
resulting from the small sample and the fact that the CV
for these indices are usually somewhat higher than those
for power (5)). It is certainly logical to argue that an athlete
performing at volitional maximal power output would
not be able to revise his or her pacing strategy and
produce still greater power on becoming aware of the
subjective symptoms of caffeine ingestion. Conversely,
an athlete performing below maximal volitional power
output may, on becoming aware of such symptoms, use
these as a cue to revise a pacing strategy and produce
greater power. Certainly, subjects in the present study
reported both perceived caffeine symptoms as well as
perceived direct effects on performance. Each subject
volunteered at least one caffeine symptom, and some-
what surprisingly, even after being informed of the
deception, none of the subjects reappraised these percep-
tions. This pattern of responses may, as Kienle and
Kiene (10) suggest, simply demonstrate a desire to please
the researchers. However, we argue that, on the basis of
previous research in psychology and medicine using
substances such as painkillers, alcohol, and caffeine, the
most parsimonious explanation is that individuals tend to
experience symptoms consistent with those of the sub-
stance they believe they have ingested.
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Interestingly, subjects 5 and 7, who reported the fewest
caffeine-related symptoms and the least confidence in
having experienced a placebo effect, also produced the
highest mean power overall. Subject 6, who produced
lowest mean power overall, reported arguably the largest
and least ambiguous placebo effect. These findings hint
at a relationship between training status and placebo
responsiveness, as suggested in previous sports perfor-
mance research (4).
Five subjects attributed direct performance effects to the
capsules, one was unsure whether to attribute performance
effects to the capsules, and one reported no performance
effects. As stated above, performance data are consistent
with the interview data of some subjects and less so with
others. This is not necessarily surprising, because we can
never be sure, even if one subject`s mean baseline and
mean experimental speeds are similar, that a placebo effect
did not bring up to par one or more experimental perfor-
mances that would otherwise have been below par, or vice
versa. Similarly, it is possible that a subject, recognizing
symptoms of caffeine ingestion, may have revised his
pacing strategy accordingly and increased his power
output, but to such a degree that he fatigued prematurely,
resulting in a below-par performance overall. It should also
be remembered that all interview responses are based on
two somewhat unreliable processes, human perception and
human recall; no amount of triangulation will unravel that
particular problem.
All subjects proposed at least one possible mechanism
that might explain observed placebo effects, and each of
these, at one level or another, involved belief. Proposals
varied from the vague (e.g., ‘‘something in the brain’’) to
the specific, such as endorphin-driven pain reduction. (The
latter proposal, placebo analgesia, a potential mechanism
that was suggested by all subjects in the present study, is
currently attracting considerable attention in contemporary
medical research and practice (6).) An interesting mecha-
nism was proposed by subject 5, a firefighter, who
described how the placebo effect might operate by
enabling him to feel less anxious and thus enable his
cardiorespiratory and musculoskeletal systems to function
more efficiently, producing greater work at a given
metabolic cost. Such a mechanism might theoretically not
be associated with any changes in physiological parameters
such as oxygen uptake or blood lactate and could explain
the lack of any observed changes in such variables in the
present study.
In summary, once a subject is informed that he or she is
to be given a substance that will enhance performance,
several subject- or environment-specific psychological
processes, such as belief, pain sensation, expectancy, and
arousal may be modified. Each of these processes might
have an impact on performance depending on its
respective direction, intensity, and valence. It is reason-
able to suggest that these processes might also be
modified on the basis of new information or feedback
once performance is under way. Thus, the search for the
mechanisms underlying the placebo effect will likely be a
complex process. Experimental designs that seek not only
to demonstrate the effect but also to provide some
explanation are required. Kirsch and Weixel (11), having
demonstrated empirically that a double-blind protocol
reduced the magnitude of placebo effects in relation to
deceptive no-blind conditions, suggested: ‘‘If double-blind
administration produces psychological effects that in
some instances are opposite to those produced by clinical
administration of drugsIthen double-blind procedures
may not be appropriate methods by which to evaluate
drug effects’’ (p. 323). Despite the requirement for either
more subjects or more trials per subject, the use of no-
placebo controls alongside placebo and experimental
conditions, or of deceptive no-blind conditions (e.g., the
balanced placebo design (14)) would give sports scientists
more insight into the mechanisms underlying many
interventions. Such approaches might also be used to
investigate the intuitively appealing proposal that placebo
and pharmacological/nutritional effects do not act in
isolation but, rather, combine in either an additive or
interactive way. It is reasonable to suggest that researchers
should also examine the impact of belief on performance,
either controlling for, or treating as independent variables,
the beliefs of subjects in intervention studies. Such
strategies might provide a clearer picture of the mecha-
nisms underlying the ergogenic effects of many commer-
cially available products and, in doing so, might allow
athletes and sports science professionals alike to make
more well-informed decisions in relation to the use of such
products.
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... O placebo é considerado um procedimento e/ou substância inerte, sem efeito farmacológico (BEEDIE et al., 2006;CLARK et al., 2000). O efeito placebo é entendido como a resposta positiva a um tratamento inerte quando comparada a uma condição controle, resultante puramente da crença que o participante teve em receber um tratamento benéfico que pudesse proporcionar melhora sobre o desfecho tratado (BEEDIE et al., 2006;COLEMAN, 2008;BENEDETTI, 2014). ...
... O placebo é considerado um procedimento e/ou substância inerte, sem efeito farmacológico (BEEDIE et al., 2006;CLARK et al., 2000). O efeito placebo é entendido como a resposta positiva a um tratamento inerte quando comparada a uma condição controle, resultante puramente da crença que o participante teve em receber um tratamento benéfico que pudesse proporcionar melhora sobre o desfecho tratado (BEEDIE et al., 2006;COLEMAN, 2008;BENEDETTI, 2014). Embora estas sejam as definições tradicionais para este fenômeno, elas não são completamente precisas, pois os placebos podem ser expressos como palavras, rituais, símbolos e significados, envolvendo um conjunto de estímulos sensoriais e sociais que resultam em uma resposta benéfica ao tratamento (BENEDETTI, 2014). ...
... Em estudos relacionados ao desempenho físico durante exercício, alguns autores verificaram melhora no desempenho devido ao efeito placebo associado a ergogênicos. Por exemplo, aumentos na potência mecânica média, potência pico, velocidade e força muscular, assim como reduções no tempo de exaustão e no tempo em testes contrarrelógio de ciclismo foram observados quando os participantes acreditavam ter ingerido cafeína (CAF) (BEEDIE et al., 2006;COLEMAN, 2008) ou carboidrato (CHO) (CLARK et al., 2000). De forma geral, a literatura científica apresenta considerável massa crítica do efeito placebo aplicado ao contexto clínico como, por exemplo, em manipulações com presença de dor, depressão e doença de Parkinson. ...
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Introdução: Placebo é considerado uma substância ou um procedimento inerte que pode proporcionar um efeito positivo ou negativo dependendo da condição em que é aplicado. É bem documentado que o placebo promove resultados positivos em condições patológicas e em condições de desempenho físico. Objetivo: Sendo assim, objetivo desse estudo é revisar em duas sessões, trabalhos que tenham abordado: 1) o efeito placebo e nocebo aplicado à clínica no tratamento da doença de Parkinson, depressão e dor, e 2) o uso do placebo como recurso ergogênico no desempenho físico. Metodologia: Para tal, uma busca foi realizada na base de dados "Pubmed" e "Web of Science". Resultados e discussão: Nesta revisão narrativa, discutimos como o efeito placebo atua em diversas condições como a dor, depressão, doença de Parkinson, e no desempenho físico, além disso, foram abordados possíveis mecanismos que possam atuar neste fenômeno. Conclusão: Podemos concluir que em condição clínica e de desempenho físico, o placebo compartilha regiões cerebrais semelhantes, que geram respostas positivas ao tratamento.
... The placebo effect is not a phenomenon unique for caffeine, as the change in motivation and selfe cacy just by the expectation of ingesting an active substance has been widely reported in the literature [11]. By using deceptive experimental designs, it has been found that a placebo can increase performance when participants are informed that the substance ingested is caffeine [12][13][14]. To date, most of the research has con rmed the placebo effect of caffeine on several forms of exercise, and by using several depictive protocols [9,10,[12][13][14][15][16][17][18]. ...
... By using deceptive experimental designs, it has been found that a placebo can increase performance when participants are informed that the substance ingested is caffeine [12][13][14]. To date, most of the research has con rmed the placebo effect of caffeine on several forms of exercise, and by using several depictive protocols [9,10,[12][13][14][15][16][17][18]. In some of these investigations, participants further increased performance when they knowingly ingested caffeine and it seems necessary that believing that they are ingesting caffeine is required to obtain an ergogenic effect [9,19]. ...
... The lack of placebo effect of caffeine in individuals habituated to caffeine may be reinforced by outcomes of previous investigations. While the placebo effect of caffeine has been con rmed by using several depictive protocols [9,10,[12][13][14][15][16][17][18], the two investigations carried out with participants habituated to caffeine showed that the deception was not successful. Foad et al. [14] found that, in participants ingesting at least 300 mg/day of caffeine, informing that they had received caffeine, when they had ingested placebo, was not effective at increasing performance during a 40-km cycling time trial. ...
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Background By using deceptive experimental designs, several investigations have observed that athletes may increase their performance when told they were given caffeine, when in fact they received a placebo (i.e., the placebo effect of caffeine). However, most of these investigations used participants not familiarized to caffeine intake, while habituation to caffeine may affect the placebo effect of caffeine. Thus, the aim of the present study was to analyze the placebo effect of caffeine on maximal strength and strength-endurance performance during the bench press exercise (BP) in healthy recreationally trained women who consume caffeine on a daily basis. Methods Thirteen resistance-trained women (BP 1RM = 40.0 ± 9.7 kg) habituated to caffeine (4.1 ± 1.7 mg/kg/day) completed a deceptive randomized experimental design with two experimental trials. On one occasion, participants were told that they would receive 6 mg/kg of caffeine but received a placebo (PLAC) and in other occasion they did not receive any substance and participants were told that this was a control situation (CONT). In each experimental trial, participants underwent a 1RM BP test and a strength-endurance test consisting of performing the maximal number of repetitions at 50% of their 1RM. Results In comparison to CONT, PLAC did not enhance 1RM (40.0 ± 10.5 vs 41.0 ± 9.5, respectively; p = 0.10), nor the number of repetitions (32.2 ± 5.1 vs 31.8 ± 4.5; p = 0.66) or mean power (130 ± 34 vs 121 ± 26; p = 0.08) in the strength-endurance test. Conclusion The expectancy induced by telling participants they were given caffeine did not modify any performance variable measured in this investigation. Thus, the use of the placebo effect of caffeine seemed an ineffective strategy to enhance muscle strength and strength-endurance during the BP exercise in women habituated to caffeine.
... Placebos have also been used in other areas, e.g., for reducing negative affect (e.g., anxiety, disgust, depression; Kirsch et al., 2008;Fournier et al., 2010;Peciña et al., 2015;Schienle et al., 2014a;Schienle et al., 2014b;Gremsl et al., 2018) and increasing physical performance (e.g., Pollo et al., 2011;Beedie and Foad, 2009) and cognitive performance (e.g., Colagiuri et al., 2011;Parker et al., 2011;Rozenkrantz et al., 2017;Weger and Loughnan, 2013). For example, so-called ergogenic placebos have increased muscle power and endurance in weight lifters and cyclists (e.g., Beedie et al., 2006;Maganaris et al., 2000). The mentioned placebos used in sport psychology and cognitive psychology are typically coupled with specific behaviors (e.g. ...
... Similar placebo approaches have been used in sport psychology and cognitive psychology. It has been shown that ergogenic placebos can increase the intensity and duration of sports training (e.g., Beedie et al., 2006, Maganaris et al., 2000. A study by Foroughi et al. (2016) on cognitive enhancement demonstrated that a placebo led to significant gains in fluid intelligence after a brief training routine (working memory task). ...
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Background : Patients with depression often experience difficulties with completing homework assignments during cognitive-behavioral therapy (CBT). In the present study, we investigated the effects of a specific placebo which aimed at improving the practice of a daily relaxation exercise during a four-week outpatient program. Methods : A total of 126 patients diagnosed with major depressive disorder were randomly assigned to one of three groups: ‘Coping with Depression’ course, ‘Coping with Depression’ course with additional daily placebo treatment, and waiting-list group. The placebo (sunflower oil) was introduced as a natural medicine to help the patients focus on their inner strengths and to mobilize their bodies’ natural healing powers. The placebo was taken orally before the daily relaxation exercise. Results : The placebo improved homework quantity and quality (both p < .001). The placebo group practiced more often and experienced greater relaxation effects than the no-placebo group. Additionally, the placebo group showed a greater reduction of depression symptoms (p < .001). Limitations : The primary limitation of the study is the lack of a psychophysiological measure of relaxation. Conclusions : Placebos can be used to leverage CBT effects in patients with depression.
... Study 1 aimed to test whether taking placebo treatment through a structured procedure could enhance the placebo outcome in a physical task. We also included a no-treatment control condition to prove the occurrence of placebo effects found in previous studies (Beedie et al., 2006;Beedie & Foad, 2009). ...
... d = 0.50). This result was consistent with the prior literature showing that placebo treatment can have a positive effect on performance (Beedie et al., 2006;Beedie & Foad, 2009). Moreover, we found that the participants who consumed the drink through a structured procedure exhibited greater performance improvement than those under the unstructured procedure condition (M structured = 29.76%, ...
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Placebo interventions have various beneficial effects on individuals' physical, mental and social well-being. We tested whether the structured procedures of placebo treatment could influence the magnitude of the placebo effects. Four studies show that a structured placebo treatment procedure can significantly enhance placebo outcomes in performance-based tasks. We attribute the enhanced placebo effects to the increased belief that a reliable link exists between action and outcomes and therefore the increased expectation regarding the efficacy of treatment, which is strengthened by the rigid structures of the placebo treatment procedure. These findings extend our understanding of the impacts of a structured treatment procedure on the magnitude of the placebo effects and shed important light on how to improve the effectiveness of placebo interventions in practice.
... For example, 'ergogenic placebos' have been administered with the verbal suggestion that they can increase muscle power and endurance in weight lifters and cyclists (e.g. Beedie et al., 2006;Maganaris et al., 2000). Placebos introduced as 'cognitive enhancers' suggested improvement of attention or memory capacity during various learning tasks. ...
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Many people find it difficult to practice progressive muscle relaxation (PMR) regularly. We attempted to improve relaxation quantity (i.e. adherence), and relaxation quality via placebo. A total of 100 women were randomly assigned to a standard group, which practiced PMR at home every day for two weeks, or a placebo group, which practiced PMR for two weeks with additional daily placebo treatment. To monitor adherence to relaxation practice, we used a smartphone app. The placebo group practiced more often than the standard group. Both groups did not differ in their reported relaxation level after the daily exercises.
... Thus, we controlled the active substance-derived expectation effects [29,48]. Although this design has controlled expectations-induced variations in performance responses [31,49], it may have induced particular cerebral responses that may not have been present in a traditional placebo-controlled clinical trial [31], as discussed earlier. ...
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Detrimental mental fatigue effects on exercise performance have been documented in constant workload and time trial exercises, but effects on a maximal incremental test (MIT) remain poorly investigated. Mental fatigue-reduced exercise performance is related to an increased effort sensation, likely due to a reduced prefrontal cortex (PFC) activation and inhibited spontaneous behavior. Interestingly, only a few studies verified if centrally active compounds may mitigate such effects. For example, carbohydrate (CHO) mouth rinse potentiates exercise performance and reduces effort sensation, likely through its effects on PFC activation. However, it is unknown if this centrally mediated effect of CHO mouth rinse may mitigate mental fatigue-reduced exercise performance. After a proof-of-principle study, showing a mental fatigue-reduced MIT performance, we observed that CHO mouth rinse mitigated MIT performance reductions in mentally fatigued cyclists, regardless of PFC alterations. When compared to placebo, mentally fatigued cyclists improved MIT performance by 2.24-2.33% when rinsing their mouth with CHO during MIT. However, PFC and motor cortex activation during MIT in both CHO and placebo mouth rinses were greater than in mental fatigue. Results showed that CHO mouth rinse mitigated the mental fatigue-reduced MIT performance, but challenged the role of CHO mouth rinse on PFC and motor cortex activation.
... It is well established that placebo effects are associated with caffeine supplementation, likely due to an expectancy surrounding its effects. Double-blind studies have shown that participants receiving a placebo treatment perceived to be caffeine improved exercise performance to a similar extent when compared with caffeine ingestion [13,14]. Positive expectation associated with caffeine ingestion appeared to drive this effect since individuals correctly believing that they had ingested caffeine improved to a greater extent than the average effect of caffeine [13,15]. ...
Article
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Caffeine is the world’s most commonly used stimulant of the central nervous system. Caffeine is present in coffee and other beverages such as tea, soft drinks, and cocoa-based foods. The caffeine expectancy questionnaire was developed to investigate the effects of caffeine expectations and thus contribute to knowledge about its usage and subjective effects (response expectancies). This study aimed to evaluate caffeine expectation psychometrically in a sample of the Brazilian population. The original version of the “Caffeine Expectancy Questionnaire (CaffEQ)” was translated and validated into Brazilian-Portuguese and adapted to Brazilian culture to be used in the Brazilian adult (19–59 y) population. After the translation and back-translation processes of the original CaffEQ questionnaire, the content and semantic validation were performed by a group of experts. The Brazilian-Portuguese version of the questionnaire consists of 47 items, in seven factors, which assess subjective perceptions about the effects of caffeine. Interobserver reproducibility and internal consistency of the questionnaire were tested with a convenience sample (n = 50) of Brazilian adult consumers of caffeine sources, who completed the Brazilian CaffEQ (CaffEQ-BR) on two occasions separated by 24 h. All of the 47 questions were adequate regarding reliability, clarity, and comprehension. Psychometric properties could be replicated consistently. Appropriate internal consistency and validation were confirmed by Cronbach’s alpha (α) 0.948, and an intraclass correlation coefficient of 0.976 was observed. The CaffEQ-BR was applied using a web-based platform to a convenience sample of Brazilian adults from all 27 Brazilian states (n = 4202 participants), along with measures of sociodemographic and caffeine consumption data. Factor validity was verified by confirmatory factor analysis. The seven factors presented a good fit for Root Mean Square Error of Approximation—RMSEA = 0.0332 (95% CI: 0.0290–0.0375). By confirming the validity and reliability of CaffEQ-BR, a useful tool is now available to assess caffeine expectations in the Brazilian adult population.
... However, where the ergogenic effects of taste tend to report painrelieving effects, placebo effects are often the result of similar mechanisms, e.g. pain, fatigue and perception of effort [112,113,131]. While taste could have direct neurobiological mechanisms, there is evidence that placebo effects can mimic the neurobiological pathways of a treatment [132]. ...
Article
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Taste is a homeostatic function that conveys valuable information, such as energy density, readiness to eat, or toxicity of foodstuffs. Taste is not limited to the oral cavity but affects multiple physiological systems. In this review, we outline the ergogenic potential of substances that impart bitter, sweet, hot and cold tastes administered prior to and during exercise performance and whether the ergogenic benefits of taste are attributable to the placebo effect. Carbohydrate mouth rinsing seemingly improves endurance performance, along with a potentially ergogenic effect of oral exposure to both bitter tastants and caffeine although subsequent ingestion of bitter mouth rinses is likely required to enhance performance. Hot and cold tastes may prove beneficial in circumstances where athletes’ thermal state may be challenged. Efficacy is not limited to taste, but extends to the stimulation of targeted receptors in the oral cavity and throughout the digestive tract, relaying signals pertaining to energy availability and temperature to appropriate neural centres. Dose, frequency and timing of tastant application likely require personalisation to be most effective, and can be enhanced or confounded by factors that relate to the placebo effect, highlighting taste as a critical factor in designing and administering applied sports science interventions.
... For example, placebo effects in sport performance are a well -documented fact. Athletes who ingested placebos in the guise of caffeine (Beedie, Stuart, Coleman, & Foad, 2006;Duncan, Lyons, & Hankey, 2009), anabolic steroids (Maganaris, Collins, & Sharp, 2000), carbohydrate (Clark, Hopkins, Hawley, & Burke, 2000), or amino acids (Kalasountas, Reed, & Fitzpatrick, 2007) performed their sport tasks better than controls. Placebos can also affect pain experience and induce an anaesthetic effect. ...
Article
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Research suggests that placebo can reduce the misinformation effect. We aimed to examine for the first time whether placebo administered in the guise of caffeine can reduce the misinformation effect. One hundred and twenty- -three healthy volunteers were randomly assigned to four groups in a 2 Placebo (Present, Not Present) × 2 Narrative (Misleading, Correct) study design. Participants from placebo groups drank 100 ml of placebo solution. They were told that it was water mixed with caffeine which could positively influence their memory. After three minutes, they watched a short movie clip as an original event and read a narrative with misleading details or correct details as a postevent information; they then completed a 22-item, two-alternative forced-choice questionnaire. The results reveal that the misinformation effect occurred. Although participants in the placebo with misinformation group scored better than participants who did not drink placebo and read the narrative containing misleading details, the difference was not statistically significant. Thus, it is concluded that placebo might not be enough to reduce the misinformation effect when it is administered in the guise of caffeine.
... Although we did blind participants by providing similar appearing drinks, they were aware of the treatments on the basis of the distinct flavor and taste of the KCA supplement. Specific studies addressing the placebo effect of caffeine on cycling performance indicate the performance benefit is on the order of 1-3% (38). In a recent review of placebo effects associated with various nutritional ergogenic aids, Hurst et al (39) conclude the overall effects are small to moderate on exercise performance (Cohen's d ¼ 0.35). ...
Article
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Background: Acute ingestion of ketone supplements alters metabolism and potentially exercise performance. No studies to date have evaluated the impact of co-ingestion of ketone salts with caffeine and amino acids on high intensity exercise performance, and no data exists in Keto-Adapted individuals. Methods: We tested the performance and metabolic effects of a pre-workout supplement containing beta-hydroxybutyrate (BHB) salts, caffeine, and amino acids (KCA) in recreationally-active adults habitually consuming a mixed diet (Keto-Naïve; n = 12) or a ketogenic diet (Keto-Adapted; n = 12). In a randomized and balanced manner, subjects consumed either the KCA consisting of ∼7 g BHB (72% R-BHB and 28% S-BHB) with ∼100 mg of caffeine, and amino acids (leucine and taurine) or Water (control condition) 15 minutes prior to performing a staged cycle ergometer time to exhaustion test followed immediately by a 30 second Wingate test. Results: Circulating total BHB concentrations increased rapidly after KCA ingestion in KN (154 to 732 μM) and KA (848 to 1,973 μM) subjects and stayed elevated throughout recovery in both groups. Plasma S-BHB increased >20-fold 15 minutes after KCA ingestion in both groups and remained elevated throughout recovery. Compared to Water, KCA ingestion increased time to exhaustion 8.3% in Keto-Naïve and 9.8% in Keto-Adapted subjects (P < 0.001). There was no difference in power output during the Wingate test between trials. Peak lactate immediately after exercise was higher after KCA (∼14.9 vs 12.7 mM). Conclusion: These results indicate that pre-exercise ingestion of a moderate dose of R- and S-BHB salts combined with caffeine, leucine and taurine improves high-intensity exercise performance to a similar extent in both Keto-Adapted and Keto-Naïve individuals.
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The race-to-race variation in performance of a top athlete determines the smallest change in performance affecting the athlete's chances of winning. We report here the typical variation in competition times of elite cyclists in various race series. Repeated-measures analysis of log-transformed official race times provided the typical variation in a cyclist's performance as a coefficient of variation. The typical variation of a top cyclist (and its 95% likely limits) was 0.4% (0.3–0.5%) in World Cup road races, 0.7% (0.7–0.8%) in Tour de France road races, 1.2% (0.8–2.2%) in the Kilo, 1.3% (0.9–2.4%) in road time trials, 1.7% (1.2–2.6%) in Tour de France time trials, and 2.4% (2.1–2.8%) in World Cup mountain biking. Cyclist interdependence arising from team tactics and pack riding probably accounts for the lower variability in performance of cyclists in road races and precludes estimation of the smallest worthwhile change in performance time for cyclists in these events. The substantial differences in variability between the remaining events, where riders act independently of each other, arise from various event-specific aspects. For these events the smallest worthwhile changes in performance time (~0.5×typical variation) are ~0.5% in the Kilo, ~0.6% in road time trials, and ~1.2% in mountain-bike races.
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A study of a sample provides only an estimate of the true (population) value of an outcome statistic. A report of the study therefore usually includes an inference about the true value. Traditionally, a researcher makes an inference by declaring the value of the statistic statistically significant or nonsignificant on the basis of a P value derived from a null-hypothesis test. This approach is confusing and can be misleading, depending on the magnitude of the statistic, error of measurement, and sample size. The authors use a more intuitive and practical approach based directly on uncertainty in the true value of the statistic. First they express the uncertainty as confidence limits, which define the likely range of the true value. They then deal with the real-world relevance of this uncertainty by taking into account values of the statistic that are substantial in some positive and negative sense, such as beneficial or harmful. If the likely range overlaps substantially positive and negative values, they infer that the outcome is unclear; otherwise, they infer that the true value has the magnitude of the observed value: substantially positive, trivial, or substantially negative. They refine this crude inference by stating qualitatively the likelihood that the true value will have the observed magnitude (eg, very likely beneficial). Quantitative or qualitative probabilities that the true value has the other 2 magnitudes or more finely graded magnitudes (such as trivial, small, moderate, and large) can also be estimated to guide a decision about the utility of the outcome.
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A qualitative investigation into the flow experiences of elite figure skaters was conducted in order to gain greater insight into the nature of flow in sport. Sixteen former US National Champion Figure Skaters, who held their titles between 1985–1990, were interviewed on an optimal skating experience, and then questioned extensively about factors associated with achieving optimal, or flow states, during performance. Factors perceived as most important for getting into flow included a positive mental attitude, positive pre-competitive and competitive affect, maintaining appropriate focus, physical readiness, and for some pairsldance skaters, unity with partner. Those factors which were perceived to prevent or disrupt flow included physical problems/mistakes, an inability to maintain focus, a negative mental attitude, and lack of audience response. The skaters placed very high value on Row-like states, and their descriptions of what was occurring during optimal skating experiences paralleled many of the characteristics of flow described by Csikszentmibalyi (1975, 1990). Drawing on the experience of elite athletes may enhance understanding of flow states as they occur in sport.
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