Effect of carbohydrate and prolonged exercise on affect and perceived exertion.
ABSTRACT It has been reported that perceptions of exertion are attenuated during prolonged cycle exercise, following CHO ingestion. However, no studies to date have examined the influence of such feedings on psychological affect during prolonged exercise, even though affect and perceived exertion are different constructs.
To examine the influence of regular CHO beverage ingestion on affect (pleasure-displeasure) and perceived exertion during prolonged cycle exercise.
In a randomized, double-blind, counterbalanced design, nine endurance trained males cycled for 2 h at 70% VO2max on two occasions, separated by 1 wk. On each occasion, they consumed either a water placebo (PLA) or a 6.4% carbohydrate-electrolyte solution (CHO) immediately before they cycled (5 mL x kg(-1) body mass) and every 15 min thereafter (2 mL x kg(-1) body mass). Pleasure-displeasure was assessed before, during, and after the prolonged bout of cycling.
During exercise, reported pleasure initially improved and was subsequently maintained in the CHO trial, in contrast to a decline reported in the PLA trial. Ratings of pleasure-displeasure were more positive during recovery in the CHO trial compared with the PLA trial (P < 0.05) and the only significant increase (P < 0.05) in pleasure occurred 15 min postexercise in the CHO trial only. RPE increased (P < 0.05) over the course of the bout of cycling and was lower (P < 0.05) 75 min into exercise in the CHO trial. Immediately postexercise, plasma glucose concentration was higher in the CHO compared with the PLA trial (P < 0.05). A main effect of trial was found for plasma cortisol concentration, with higher values reported in PLA trial.
Results suggest that CHO ingestion enhanced feelings of pleasure during and following prolonged cycling and highlighted the importance of assessing not only "what," but also "how" a person feels.
[show abstract] [hide abstract]
ABSTRACT: A series of studies have reported that a high carbohydrate meal, or diets high in carbohydrate, were associated with feeling less energetic. However, after a drink containing pure sugar most studies report no effect. Meals almost exclusively carbohydrate increase the availability of tryptophan and hence serotonin synthesis in the brain, however, a small amount of protein blocks this mechanism making it an uncommon response. In many individuals, poor mood stimulates the eating of palatable high carbohydrate/high fat foods that stimulate the release of endorphins. There is a tendency for those with lower blood glucose, when performing cognitively demanding tasks, to report poorer mood. In a range of situations an association between a tendency for blood glucose levels to fall rapidly, and irritability, has been found. Differences in the ability to control blood glucose levels influence the association between carbohydrate intake and mood. There is a need in future research to contrast the impact of carbohydrate on mood in those distinguished because of their pre-existing psychological and physiological functioning.Neuroscience & Biobehavioral Reviews 06/2002; 26(3):293-308. · 8.65 Impact Factor
[show abstract] [hide abstract]
ABSTRACT: A series of three studies examined the influence of glucose drinks and increasing blood glucose levels on mood. Experiment one considered the short-term effect of a glucose containing drink on mood in young adults: a glucose drink in the morning and higher blood glucose levels were both associated with feeling less tense. Higher blood glucose was also correlated with greater self-reported energy. In the second experiment high blood glucose levels were sustained for 2 hr by repeatedly taking a glucose containing drink. Again higher blood glucose levels were associated with reports of less tension. In a final study subjects were placed in a frustrating situation. The consumption of a glucose drink resulted in fewer negative responses, following a negative statement from the experimenter, in subjects who had fasted over-night. It was concluded that higher blood glucose levels are associated with feeling less tense.Journal of Psychosomatic Research 11/1993; 37(7):723-35. · 3.30 Impact Factor
[show abstract] [hide abstract]
ABSTRACT: The purpose of the present study was twofold: first, to assess the effect of prolonged intense exercise on total neutrophil elastase content in endurance-trained cyclists and to determine whether this is associated with postexercise falls in lipopolysaccharide (LPS)-stimulated neutrophil elastase release; and second, to determine the effect of carbohydrate (CHO) ingestion during exercise on these responses. In a randomized design, nine trained male cyclists cycled for 2 h at 75% VO(2max) on two occasions with either CHO (6.4%, i.e., 64 g x L-1) or placebo (PLA) beverage ingestion before (5 mL x kg-1), during (2 mL x kg-1), and after (5 mL x kg-1) the exercise. Venous blood samples were obtained at rest, immediately postexercise, and at 1 h postexercise. After exercise, CHO ingestion was associated with a higher plasma glucose concentration (P < 0.05) and fewer numbers of circulating neutrophils compared with the PLA trial (P < 0.01). Neither exercise nor CHO ingestion affected total neutrophil elastase content, yet LPS-stimulated neutrophil elastase release fell postexercise by approximately 47% on the PLA trial (P < 0.01). Values did not change significantly from preexercise on the CHO trial. These findings suggest that neither exercise nor CHO-beverage ingestion influences the total elastase content of neutrophils. Therefore, changes in neutrophil elastase content cannot account for the fall in LPS-stimulated neutrophil elastase release after prolonged intense exercise or for the blunting of this response with CHO ingestion.Medicine & Science in Sports & Exercise 09/2003; 35(8):1326-32. · 4.43 Impact Factor
Psychobiology and Behavioral Strategies
Effect of Carbohydrate and Prolonged
Exercise on Affect and Perceived Exertion
SUSAN H. BACKHOUSE', NICOLETTE C. BISHOP2, STUART J. H. BIDDLE2, and CLYDE WILLIAMS2
1Carnegie Research Institute, Carnegie Faculty of Sport and Education, Leeds Metropolitan University, Leeds, UNITED
KINGDOM; and 2School of Sport and Exercise Sciences, Loughborough University, Loughborough, UNITED KINGDOM
BACKHOUSE, S. H., N. C. BISHOP, S. J. H. BIDDLE, and C. WILLIAMS. Effect of Carbohydrate and Prolonged Exercise on Affect
and Perceived Exertion. Med. Sci. Sports Exerc., Vol. 37, No. 10, pp. 1768-1773, 2005. Introduction: It has been reported that
perceptions of exertion are attenuated during prolonged cycle exercise, following CHO ingestion. However, no studies to date have
examined the influence of such feedings on psychological affect during prolonged exercise, even though affect and perceived exertion
are different constructs. Purpose: To examine the influence of regular CHO beverage ingestion on affect (pleasure-displeasure) and
perceived exertion during prolonged cycle exercise. Methods: In a randomized, double-blind, counterbalanced design, nine endurance
trained males cycled for 2 h at 70% VO2.a_ on two occasions, separated by 1 wk. On each occasion, they consumed either a water
placebo (PLA) or a 6.4% carbohydrate-electrolyte solution (CHO) immediately before they cycled (5 mL.kg-' body mass) and every
15 min thereafter (2 mL.kg-1 body mass). Pleasure-displeasure was assessed before, during, and after the prolonged bout of cycling.
Results: During exercise, reported pleasure initially improved and was subsequently maintained in the CHO trial, in contrast to a
decline reported in the PLA trial. Ratings of pleasure- displeasure were more positive during recovery in the CHO trial compared with
the PLA trial (P < 0.05) and the only significant increase (P < 0.05) in pleasure occurred 15 min postexercise in the CHO trial only,
RPE increased (P < 0.05) over the course of the bout of cycling and was lower (P < 0.05) 75 min into exercise in the CHO trial.
Immediately postexercise, plasma glucose concentration was higher in the CHO compared with the PLA trial (P < 0.05). A main effect
of trial was found for plasma cortisol concentration, with higher values reported in PLA trial. Conclusion: Results suggest that CHO
ingestion enhanced feelings of pleasure during and following prolonged cycling and highlighted the importance of assessing not only
"what," but also "how" a person feels. Key Words: AFFECT, RPE, PLEASURE-DISPLEASURE, CHO INGESTION. CYCLING
he benefits of CHO ingestion during prolonged (>90
min) continuous exercise have been well docu-
mented (11). The literature is consistent in showing
that CHO feedings can delay fatigue in a variety of exercise
protocols by maintaining blood glucose and in some cases
sparing muscle glycogen levels, both being important
sources of energy for working muscles. In addition, the
notion that CHO ingestion influences perceptions of exer-
tion during prolonged cycling exercise has been well doc-
umented in the recent literature (8,20,29).
To our knowledge, research has yet to examine the in-
fluence of CHO ingestion on affective states ("how" a
person feels) during prolonged cycling. As noted earlier,
Address for correspondence: Dr. Susan H. Backhouse, Carnegie Research
Institute, Carnegie Faculty of Sport and Education, Leeds Metropolitan
Campus, Leeds, LS6 3QS, UK: E-mail:
Submitted for publication December 2004.
Accepted for publication May 2005.
MEDICINE & SCIENCE IN SPORTS & EXERCISE,
Copyright © 2005 by the American College of Sports Medicine
previously the focus has been on "what" a person feels, as
measured by the RPE scale. Therefore, in accordance with
the assertion of Hardy and Rejeski (19) that the RPE on its
own provides limited information about the subjective ex-
periences of individuals during exercise, "what" and "how"
a person feels were examined during a prolonged exercise
session. This was facilitated by the administration of the
Borg (7) RPE scale, a measure of "what" a person feels, and
the Feeling Scale (FS) (19) as the measure of "how" a
The administration of both scales in the present study
provides a more encompassing representation of the subjec-
tive exercise experience because affect and perceived exer-
tion are not isomorphic constructs (19). In support of this
assertion are previous studies (1,19) that have reported that
the correlations between the FS and RPE scale change
across a range of exercise intensities, but generally never
exceed a moderate level (approximately -0.6, leaving a
large proportion of the variance in each unaccounted for).
Furthermore, a linear response to incremental exercise is
often reported using the RPE scale, which differs from the
curvilinear responses elicited using the FS (14). It is not
surprising that a linear relationship is often reported because
the Borg RPE scale was originally designed to facilitate
linearity of RPE values with HR (6). This supports the
importance of administering additional subjective measures
during exercise studies because, as stated previously (19),
two individuals may report the same perception of exertion
on the RPE scale (e.g., "hard," 15), but this may be accom-
panied by feelings of pleasure in one individual and dis-
pleasure in another. One can also distinguish affect .from
perceived exertion based on the neuroanatomical and neu-
rophysiological mechanisms involved as they differ beyond
the level of the brainstem. It appears that the thalamus-
insula-somatosensory, cortex forms the basis of perceived
exertion.(10) and the thalamus-amygdala-nucleus accum-
bens axis forms the basis of affective responses (9,22).
Therefore, even though the relationship between CHO in-
gestion and RPE has been documented previously, such
conceptual differences support the need for further investi-
gations into the role of CHO ingestion on subjective states
A number of studies have been reported in the literature
that have examined the influence that glucose-containing
drinks exert on affective states at rest (2,3). Benton and
Owens (3) concluded that higher blood glucose levels (that
were within the normal range) were associated with lower
reported tension. Negative affect has also been associated
with low blood glucose in insulin-dependent diabetics (17)
and in individuals experimentally manipulated into a hypo-
glycemic state (15). It has also been reported that CHO
ingestion resulted in improved affective states during pro-
longed training periods in field hockey players (21). Two
recent studies (30,32),have considered the relationship be-
tween CHO feedings and affect among other factors during
intermittent high-intensity exercise. However, these inves-
tigations by Welsh et al. (30) and Winnick et al. (32)
focused on specific states, such as fatigue, and inconsistent
patterns were reported. Few studies have examined the
possible link between CHO feedings and affective states
during exercise, which is unfortunate because whether one
feels good or bad during exercise is clearly an important
factor. Indeed, it could determine the outcome of a compet-
itive event and also impact on task persistence (1). There-
fore, given the relationships previously documented in the
literature, it was hypothesized that affective states .may be
influenced by CHO ingestion during prolonged exercise.
Based on studies at rest, we speculated that the effects might
be due to changes in blood glucose level and therefore
activation of the autonomic nervous system in an attempt to
return blood glucose concentration to normal levels (2). It
was also hypothesized that, in accordance with previous
studies investigating CHO ingestion and RPE during cy-
cling exercise (8,13), an attenuation in RPE would be ob-
served following CHO ingestion.
Despite more than three decades of research concerning
the exercise-affect .relationship, there is, and continues to
be, a void in the literature on prolonged exercise. There is a
strong advocacy that exercise makes people "feel better";
however, aside from a study by Acevedo et al. (1), affective
changes during.and following prolonged constant-paced ex-
ercise have not been identified. Indeed, Acevedo and col-
leagues (1) reported that ratings of pleasure progressively
declined during a 2-h constant-paced run at 70% VO2ma.,
whereas RPE progressively increased. This is in contrast to
the positive affect that Morgan (24) suggests is experienced
by some runners after the first hour of a run (based on
anecdotal accounts). The present study, although focusing
predominantly on the effect of CHO ingestion, also enables
a further examination of such discrepancies in prior re-
Therefore, the purpose of this study was to examine the
effects of CHO ingestion and prolonged (i.e., 120 min)
exercise on pleasure--displeasure and perceived exertion.
This study was performed as part of an investigation
examining the role of CHO ingestion on immune measures,
the data from which have already been published (4).
Participants. Nine endurance trained males (mean ±
SEM; age 25 ± 2 yr; height 191 ± 4 cm; body mass 76.8
± 2.8 kg; VO2max, 64.7± 2.7 mL-kg- 1min71) volunteered
to participate in this study. All participants were fully in-
formed of the nature and purpose of the study before signing
a statement of informed consent. The study had the approval
of the ethical advisory committee of Loughborough
Measures of affect and perceived exertion. The
FS (19) was used as a measure of the affective dimension of
pleasure-displeasure. Commonly used for the assessment of
affective responses during exercise, it is an El-point single-
item bipolar rating scale. The scale ranges from -5 to +5.
Anchors are provided at the 0 point ("neutral") and at all odd
integers, ranging from "very good" (+5) to "very bad"
(-5). Participants were asked to rate how they felt at that
particular moment. The FS was administered preexercise,
every 15 min throughout the prolonged cycle, upon cessa-
tion of exercise, and 5, 15, and 30 min postexercise (Fig. 1).
The RPE scale (7) was used as a measure of perceived
exertion during exercise and was administered every 15 min
during the trial (Fig. 1). The scale ranges from 6 to 20, with
anchors ranging from "very, very light" to "very, very
hard." The FS was presented first, followed by the RPE
Preliminary procedures. Maximal oxygen uptake
was estimated by means of a continuous incremental exer-
sen. P0ationg ofPe10ei55J
ri expe tal Cprotiool,
FIGURE 1--Schematic representation of the experimental protocol.
CHO INGESTION, AFFECTIVE STATES, AND CYCLING
c w vs
Medicine & Science in. Sports & Exercisea
cise test on an electrically braked cycle ergometer (Lode
Excalibur, Groningen, The Netherlands) to volitional
fatigue. From the V02-work relationship, the work rate
equivalent to 70% VO2maX was interpolated. Please refer
to Bishop et al. (4) for further details of the preliminary
Nutritional control. Participants reported for each ex-
perimental trial following an overnight fast of between 10
and 12 h. This was to ensure that participants began each
trial with an empty stomach, thus eliminating any negative
effect that a previous meal might have had, both on exercise
metabolism and gastric emptying. For the 48 h before the
experimental trial, participants refrained from any strenuous
physical activity. Participants consumed their normal diet,
but weighed and recorded food eaten in a food diary during
the 48 h before the first trial. This diet was then replicated
during the corresponding period before any other further
trials. This information was later analyzed using COMP-
EAT (Nutrition Systems, London). In addition, caffeine and
alcohol were also prohibited during the 48 h before the trial
because both have been found to have transient effects on
affective states (27).
Experimental procedures. In a randomized, double-
blind, counterbalanced design, participants completed two
exercise trials, each separated by at least 7 d. On each
occasion, participants consumed either a carbohydrate
(6.4%) solution (CHO) flavored with lemon or a placebo
solution (PLA) that was artificially sweetened and flavored
with lemon. Each drink was identical in flavor and appear-
ance, and participants were not aware of the content of the
drinks in each trial. These solutions were ingested immedi-
ately before exercise (5 mL-kg-1 body mass), every 15 min
during (2 mL.kg-' body mass), and 5 min postexercise (5
mL-kg-1 body mass).
Participants reported to the laboratory at 8:00 a.m. on
each occasion following an overnight fast. Upon arrival,
they responded to the FS. They then emptied their bladders
before body mass (in shorts only) was measured. Partici-
pants were then seated quietly for 15 min after which a
blood sample was taken from an antecubital vein by veni-
puncture. They then performed a 2-h cycle ergometer ride
on an electronically braked ergometer (Lode Excalibur)
(Fig. 1). Participants began cycling at 70% VO2max and,
although the intensity was monitored, they completed the
exercise without continual adjustment of the resistance. The
FS was administered at 15-min intervals. Expired air sam-
ples were obtained using the standard Douglas bag method
at 20, 50, 80, and 110 min during the exercise bout to
determine exercise intensity. A paramagnetic oxygen ana-
lyzer (Servomex 1420B, Crowborough, UK) and an infrared
carbon dioxide analyzer (Servomex 1415B) were used along
with a dry gas meter (Harvard Apparatus, Edenbridge, UK)
for determination of V02 and VCO2. HR were recorded
every 15 min during exercise using short-range telemetry
(Sportester®, Polar Electro, Kempele, Finland).
Upon cessation of the exercise task, participants imme-
diately responded to the FS. Participants once again re-
sponded to this measure 5, 15, and 30 min postexercise.
Official Journal of the American College of Sports Medicine
Further blood samples were taken immediately postexercise
and at I h postexercise. No food was consumed during this
period, and fluid ingestion was as prescribed.
Blood analyses. Blood samples were collected into
monovette tubes (Sarstedt, Leicester, UK), containing lith-
ium heparin and were centrifuged at 1500 X g at 4°C for 10
min within 15 min of sampling. The plasma obtained was
immediately stored at minus 70'C for later analysis for
glucose and cortisol using hexokinase (No. 16-50 Kit,
Sigma, Poole, UK) and 1251 radioimmunoassay (ICN Phar-
maceuticals, Costa Mesa, CA) methods, respectively. Ra-
dioactivity was measured using an automated gamma
counter (Cobra II, Packard Instruments Co. Inc.). For further
details of the analysis procedures, the reader is referred to
Bishop et al. (4).
Statistical analysis. A series of two-way ANOVA for
repeated measures on two factors (experimental condition
and sampling time) was used to examine the affective,
physiological, metabolic, and perceived exertion data. For
the FS ratings, separate ANOVA were conducted on the pre-
to postexercise time points (pre, post 0, post 15, post 30) and
during-exercise time points (from 15 to 120 min). This
approach allowed direct comparisons during exercise be-
tween the FS and RPE scale. Significant main effects were
further analyzed using paired t-tests and the Bonferroni
adjustment for the number of pairwise comparisons was
employed. Greenhouse-Geisser epsilon corrections were
used when the sphericity assumption was violated. Statisti-
cal significance was set at the 0.05 level, apart from the
Bonferroni analyses. Values are presented as means (SEM).
Diet. A nutrient analysis of the 2-d food records before
each of the two exercise sessions revealed no differences in
the energy intake and nutrient composition between condi-
tions. The mean energy intake of the participants was 2322
kcal-d-1, with the proportion of energy being 64.1% ±
3.7% from CHO, 19.6% ± 3.0% from fat, and 17.3 ± 0.8%
Physiological responses to the exercise proto-
col. HR and %V/O2max did not differ between trials with
the mean VO2ma, during exercise being 74.2 ± 1.3% in the
CHO trial compared with 75.2 ± 1.4% in the PLA trial, thus
demonstrating that the participants were exercising at the
same relative exercise intensity in both conditions. HR
during exercise ranged from 158 to 170 bpm.
Plasma glucose. Plasma glucose concentration was
higher immediately postexercise in the CHO trial (6.1 ± 0.3
mmol.L-1) than the PLA trial (5.4 ± 0.3 mmol'L-1),
and there was a significant interaction for treatment X time
(F(2,16) = 7.6; P < 0.05). This showed that in the CHO trial,
blood glucose concentration increased from preexercise to
immediately postexercise, whereas in the PLA trial, the
concentration remained stable from preexercise to post 0,
and by 1 h postexercise had fallen to a concentration lower
than that observed preexercise (Table 1).
TABLE 1. Changes in blood glucose and cortisol concentration during the 120-min cycle (mean ± SEM).
6.1 ± 0.3
588 t 74
5.4 ± 0.3
811 ± 153
Post 1 h
5.3 ± 0.2
477 ± 60
Post 1 h
5.0 ± 0.2
641 ± 99
Cortisol: main effect for trial, P < 0.05; glucose: main effect for trial, time and trial x time interaction, P < 0,05.
5.2 ± 0.1
528 ± 23
5.4 ± 0.1
576 ± 46
Plasma cortisol. Plasma cortisol concentrations in-
creased by 11% during the CHO trial (528 :t 23 to 588 ±
74 nmol.L-1) and by 24% (576 ± 46 to 811 ± 153
nmol.L-1) in the PLA trial, but this increase across both
trials was not statistically significant due to large varihbility
(Table 1). Overall, there was a main effect for trial, with
values being higher in the PLA trial (F(, 8) 8.7; P < 0.05)
compared with the CHO trial.
Pleasure-displeasure. Analysis on the FS revealed
that during exercise, an overall main effect for treatment
was observed (F(,, 8) = 8.5; P < 0.05), but not time. Overall
ratings of pleasure were higher during the CHO trial, com-
pared with the PLA trial. Pleasure ratings became more
positive and were maintained throughout exercise in the
CHO trial, whereas in the PLA trial, ratings became less
positive (Fig. 2). Analysis of the pre- to postexercise
changes revealed a significant interaction effect (F(4, 32) =
2.77; P < 0.05) with ratings of pleasure being higher overall
in the CHO trial compared with the PLA trial, and pleasure
improved from preexercise to 15 min postexercise in the
CHO trial only (Fig. 2).
Rating of perceived exertion. RPE increased over
time (F(7, 56) = 21.1; P < 0.001) across both conditions.
There was an interaction of treatment X time (F(7, 56) = 2.6;
P < 0.05), with RPE being significantly lower only at 75
min in the CHO trial compared with the PLA trial (Fig. 3).
Correlations. The correlations between the FS and
RPE scale were weak. All correlations were of negative
direction; however, only one was significant (90 min, PLA
trial; -0.75, P < 0.05). The remainder displayed low to
moderate (range: -0.02 to -0.63), nonsignificant correla-
tions, demonstrating that the FS and RPE are conceptually
In the present study, we observed that ratings of pleasure-
displeasure changed as a result of prolonged cycling and that
CHO supplementation appeared to influence this response.
,Repeated in-task assessment of pleasure-displeasure led to
the observation that CHO ingestion noticeably influenced
"how" participants felt during and following exercise as
measured by the FS. This study highlights the importance of
assessing this psychological parameter in addition to the
often administered RPE scale because "what" the partici-
pants felt was reduced by CHO ingestion to a much lesser
extent. Furthermore, we found no significant correlations
between the FS and RPE scale over the course of the trial,
supporting the assertion that affect and perceived exertion
are not isomorphic constructs (19).
Based on previous studies at rest, we hypothesized that
affect would be positively maintained in the CHO trial. Our
data supported this hypothesis as pleasure-displeasure was
observed to shift in opposite directions when the CHO and
PLA trials were compared, with participants in the CHO
trial reporting a more pleasurable exercise experience.
FIGURE 2-Pleasure--displeasure (FS) be-
fore, during, and following the 120-min bout
of cycling (overall main effect of condition
during exercise; P < 0.05).
45 60 75
90 105 120
CHO INGESTI6N, AFFECTIVE STATES, AND CYCLING
I I I I I
P5 P15 P30 P60
Medicine & Science in Sports & Exercise®
FIGURE 3-Rating of perceived exertion during the 120-min bout of
cycling; *P < 0.05, CHO vs PLA.
Indeed, the ingestion of CHO during exercise prevented
the observed reduction in pleasure noted in the PLA trial
(Fig. 2). We also hypothesized that CHO ingestion during
exercise would attenuate RPE, but this was limited to the
75th minute of exercise. Consequently, future studies
should continue to employ both scales in order to obtain
a more complete understanding of the subjective exercise
Although this study was not designed to uncover the
mechanisms by which CHO feedings improve affect, a
number of mechanisms have been previously described at
rest (2) and the findings of this study could offer support
for one of the propositions during exercise. The overall
differences during exercise in pleasure- displeasure be-
tween the CHO and PLA trials could be linked to the
physiological changes observed following the 120-min
cycle. Immediately postexercise, blood glucose concen-
trations were higher (P < 0.05) following the CHO trial.
This is consistent with findings that low blood glucose
concentrations are associated with negative affective
states (15,17). Although participants in the PLA trial did
not become hypoglycemic, glucose concentrations were
markedly lower. However, the adequacy of this mecha-
nism in explaining the link between CHO ingestion and
affect during exercise remains to be elucidated. In addi-
tion, there was a main effect for trial on plasma cortisol
concentration, with overall values being higher following
the PLA trial than the CHO trial. This is consistent with
the findings of Utter et al. (29) who reported lower
cortisol concentrations during the later stages of a 2.5-h
bout of cycling at approximately 75% VOEmax. According
to Morgan et al. (23), such findings may indicate that the
PLA trial was more stressful, both perceptually and phys-
iologically. Cortisol is often secreted in response to emo-
tional stress and unpleasant sensations (26) and the re-
duction in pleasure noted in the PLA trial would support
this suggestion. Rudolph and McAuley (28) have empha-
sized that the role that cortisol might play in affective
responses to acute exercise has received minimal atten-
Official Journal of the American College of Sports Medicine
tion. Indeed, a number of studies have reported an asso-
ciation between increased cortisol levels and increases in
negative affective states (16) and further investigations
may be warranted.
As highlighted, the relationship between CHO ingestion
and RPE during prolonged exercise has been well docu-
mented (8,20,29), and findings indicate that CHO availabil-
ity attenuates RPE during the latter stages of exercise
(29,3 1). This study offers tentative support for such findings
as RPE was lower 75 nin into exercise compared with the
PLA trial. However, such a reduction was not sustained and
it is not clear why the effect was limited to 75 min into
exercise. In agreement with previous studies involving cy-
cling (12), blood glucose concentration was influenced by
CHO supplementation, with higher concentrations noted
following exercise in the CHO trial. Although blood sam-
ples were not collected during exercise, they were collected
as soon as the exercise bout was complete and therefore still
offer partial support for the assertion by Coggan and Coyle
(12) that, during cycling exercise, reductions in RPE fol-
lowing CHO ingestion may be a function of elevated cir-
culating levels of blood glucose.
This study was also designed to determine the impact of
prolonged exercise on the temporal dynamics of pleasure-
displeasure. Unlike the RPE scale, FS ratings can be bidirec-
tional and research is consistently observing something of a
"rebound" pattern immediately following exercise that has
induced negative responses during exercise (1,5,18). The
present study offers further support for this phenomenon (Fig.
2). It appears that the trajectory of pleasure-displeasure during
and following exercise exhibits two distinct phases. The first
phase involves the decline during exercise and the second
phase an improvement following exercise (1,5,25). In the PLA
trial, if only pre- to postexercise changes had been considered,
the decline in reported pleasure during the exercise bout would
have been masked. We also found that prolonged cycling
elicited positive affective changes 15 min postexercise, but this
was restricted to the CHO trial only. Therefore, it appears that
nutritional intervention during prolonged exercise may be a
key determinant of the exercise experience and should be
considered in future studies.
In summary, our results suggest that CHO ingestion can
attenuate the reductions in pleasure that occur when only
fluid and electrolytes are ingested. Therefore, athletes,
coaches, and sport and exercise scientists can extrapolate
from this study the observation that CHO ingestion during
exercise also influences the athlete's psychological state, as
assessed by the FS, adding to the literature on physiological,
performance, and exertional effects. RPE was also reduced
in the CHO trial, but only at 75 min. In sum, these results
show that CHO ingestion exerts differential effects on affect
and perceived exertion and emphasize the importance of
assessing not only "what" but also "how" a person feels
The authors thank GlaxoSmithKline (Coleridge, UK) for supplying
the test drinks. This work was undertaken while S. H. Backhouse
was at Loughborough University.
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CHO INGESTION, AFFECTIVE STATES, AND CYCLING
Medicine & Science in Sports & Exercise,&
TITLE: Effect of Carbohydrate and Prolonged Exercise on Affect
and Perceived Exertion
SOURCE: Med Sci Sports Exercise 37 no10 O 2005
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