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ORIGINAL ARTICLE
The stress of chess players as a model to study the effects
of psychological stimuli on physiological responses: an example
of substrate oxidation and heart rate variability in man
Nicolas Troubat ÆMarie-Agnes Fargeas-Gluck Æ
Mikko Tulppo ÆBenoit Dugue
´
Accepted: 15 October 2008 / Published online: 6 November 2008
ÓSpringer-Verlag 2008
Abstract We have studied the physiological conse-
quences of the tension caused by playing chess in 20 male
chess players, by following heart rate, heart rate variability,
and respiratory variables. We observed significant increase
in the heart rate (75–86 beats/min), in the ratio low fre-
quency (LF)/high frequency (HF) of heart rate variability
(1.3–3.0) and also a decrease in mean heart rate variability
with no changes in HF throughout the game. These results
suggest a stimulation of the sympathetic nervous system
with no changes in the parasympathetic system. The
respiratory exchange ratio was rather elevated (over 0.89)
at the start and significantly decreased during the game
(0.75 at the end), indicating that energy expenditure pro-
gressively switched from carbohydrate to lipid oxidation.
The changes in substrate oxidation and the sympathetic
system seem to be due to high cognitive demands and bring
new insight into adaptations to mental strain.
Keywords Chess Heart rate variability
Indirect calorimetry Psychological crossover concept
Psychological stress Substrate oxidation
Introduction
Traditionally, the effects of psychological stress in man
have been investigated using two different kinds of situa-
tions: laboratory experiments and real-life stressors.
Laboratory tests (e.g. speech tasks, arithmetic tasks, Stroop
test, etc.) consist of a stimulus of short duration and of
limited potency. Investigations using real-life stressors can
be divided into those using chronic stressors (e.g.
bereavement, unemployment, divorce, caring for patients
with Alzheimer’s disease, etc.) and acute stressors (e.g.
academic exams). One advantage of using arranged stress
situations (laboratory tests and real-life stressors) is that
one can easily use each individual as his or her own con-
trol. However, because of ethical and legal considerations,
it is difficult to experimentally induce pure psychological
stress. Also, it is difficult to avoid unnatural and artificial
arrangements (Dugue
´et al. 1992,2001).
Stress is often defined as a threat (real or implied) to
homeostasis (McEwen and Wingfield 2003) and is known
to stimulate the autonomic nervous system, which in turn
stimulates the cardiovascular system and the metabolism.
Mental effort induces the mobilization of energy for cog-
nitive purposes and induces a compensatory strategy to
protect performance in the presence of augmented request
tasks and psychological stressors (Gaillard 1993,2001).
Though it is well known that glucose is used as a primary
fuel for energy generation in the brain during psychological
stress or mental effort (Rao et al. 2006; Fairclough and
Houston 2004; Sourkes 2006), very little information is
available concerning the global metabolism of substrates
during mental strain. This lack of exploration may be the
result of drawbacks to the available techniques that disturb
the subject during investigation, of difficulties in applying
these techniques, and of continuously monitoring subjects
N. Troubat M.-A. Fargeas-Gluck B. Dugue
´(&)
UFR Sciences du Sport de l’Universite
´de Poitiers et Laboratoire
des Adaptations, Physiologiques aux Activite
´s Physiques
(EA 3813), 4 alle
´e Jean Monnet, 86000 Poitiers, France
e-mail: benoit.dugue@univ-poitiers.fr
M.-A. Fargeas-Gluck
Department of Sport Sciences,
University of Limoges, Limoges, France
M. Tulppo
Department of Physical Rehabilitation, Verve, Oulu, Finland
123
Eur J Appl Physiol (2009) 105:343–349
DOI 10.1007/s00421-008-0908-2
through a mental challenge. However, with the develop-
ment of new generation of portable metabolic systems, it is
now possible to monitor cardio-respiratory variables during
a challenging situation with only minor disturbances.
A chess game represents a legitimate psychological
stress. It is a strategic and high cognitive demand task.
Players have to think through a wide range of move
sequences to find the best choice. This very challenging
and interesting situation has not been thoroughly explored,
and to date, most of the reports have concentrated on
psychological measurements and not on physiological
outcomes. The only available study in that field was the
one of Schwarz et al. (2003).
Accordingly, we studied the effect of the tension caused
by playing a chess game on heart rate, heart rate variability,
and respiratory variables. Using indirect calorimetry, we
deduced the oxidation rate of lipids and carbohydrates and
also total energy expenditure during the challenge. More-
over, we investigated the influences of the expertise of the
players on the physiological responses in this atypical
sport.
Subjects and methods
Subjects
A total of 20 male chess competitors of national and
international level (age: 42 ±13 years; height: 178 ±
4 cm; weight: 76 ±9 kg; BMI: 24 ±3kgm
-2
) partici-
pated in our study. They were subjectively healthy, and
none were on medication. The experiment was conducted
in accordance with the Declaration of Helsinki, and all the
procedures were carried out with written informed consent
of the participants. Volunteers were classified according
their ELO score (official rating of the International Chess
Association). The group of our subjects had an ELO (mean
and extreme values) of 1,757 (1,250–2,170).
Study design
The experiment started with the lunch (standardized) of the
participants, which was taken between 12.00 and 13.00.
Then at 16.30, the participants started their chess session.
Before the start of the experiment, instructions were given
to the participants about the procedures and protocol
requirements during the test. In order to make the partici-
pants comfortable, they were asked to relax in a supine
position for 15 min. Moreover, all participants underwent a
familiarization period with the equipment required for
testing. The experimental room was calm (no more than 2
observers and the player) and light and temperature (18°C)
were continuously regulated.
Chess game
The participants played a chess game against a computer
with software that mimed a level of expertise which was
similar to the player’s level (Chessmaster 9th edition,
2004). This software was used because of the ability to
select a wide range of ELO levels. In fact, without telling
the participants, we set the program at a slightly higher
level (?100 ELO points) than the level of the player. A
laboratory assistant who was familiar with chess was
always present during experiments. He performed the
moves indicated by the computer on the chess board, and
he also served as the human presence in front of the par-
ticipants. One hour was allotted for each player (an
electronic clock was used to control the time). Cardio-
respiratory variables were continuously recorded until the
chess game were over (approximately 90 min, the com-
puter also needed some time before indicating its move).
Psychological measurements
PANAS
This test presents 20 adjectives, 10 that assess positive
affectivity (e.g., excited) and 10 that assess negative
affectivity (e.g., upset) (Watson et al. 1988). These adjec-
tives describe different feelings and emotions. Participants
described their present feelings on a five point scale,
ranging from ‘‘very slightly’’ (1) to ‘‘extremely’’ (5).
Brief COPE (dispositional version of trait anxiety)
This test is the abridged version of the COPE inventory
(Carver et al. 1989) and presents 14 scales that assess dif-
ferent coping dimensions: active coping, planning, using
instrumental support, using emotional support, venting,
behavioral disengagement, self-distraction, self-blame,
positive reframing, humor, denial, acceptance, religion, and
substance use. Each seven point scale, ranging from ‘‘never’’
(1) to ‘‘always’’ (7), contains two items (28 items altogether).
Both questionnaires were presented before the start of
the experiment.
Physiological measurements
A portable metabolic measurement system (Vmax ST;
Sensor Medics, Germany) and a heart rate monitor (Polar
S810, Finland) were used to measure the cardio-respiratory
responses and heart rate variability. The gas analyzer sys-
tem was calibrated before each subject session using gases
of known concentrations and used thereafter as previously
described (Brehm et al. 2004; Laurent et al. 2008). The
following variables were recorded throughout the game:
344 Eur J Appl Physiol (2009) 105:343–349
123
heart rate (HR), ventilatory flow (VF), tidal volume (Vt),
breath frequency (bF), O
2
consumption ð_
VO2Þ;CO
2
pro-
duction ð_
VCO2Þ;respiratory exchange ratio (RER), and the
following indices were analyzed after the test: mean R–R,
low frequency (LF), high frequency (HF)—an index of the
activity of the parasympathetic branch of the autonomic
nervous system, LF/HF ratio (LF/HF)—an index of the
activity of the sympathetic branch of the autonomic ner-
vous system, carbohydrate oxidation rate (CHO), lipid
oxidation rate (FAT), and energy expenditure (EE). The
baseline measurements were carried out before the begin-
ning of the match in sitting posture during 3 min.
Data processing
The R–R intervals were recorded (Polar S810, Finland) at a
frequency of 1,000 Hz (Ruha et al. 1997) and saved in a
computer for further analysis of HR variability from the R–
R interval tachogram with Heart Signal software (Kempele,
Finland). All the R–R intervals were edited by visual
inspection, to exclude all the undesirable beats, which
accounted for \1% in every subject. The details of this
analysis and the filtering technique have been described
previously (Huikuri et al. 1992,1996). The mean R–R and
the standard deviation of all R–R intervals were used as
time domain analysis methods. An autoregressive model
(model order 20) was used to estimate the power spectrum
densities of heart rate variability. The power spectra were
quantified by measuring the area under the whole fre-
quency band (total power) and under two frequency bands:
LF power, from 0.04 to 0.15 Hz; and high-frequency
power (HF), from 0.15 to 0.4 Hz. We also calculated LF
and HF in normalized units (n.u) with the same algorithm.
Series of 300 s or approximately 256 consecutive R–R
intervals (which is a minimal time requirement) were
extracted 5 min before the game, at the beginning, at the
middle, and at the end of each game. The same periods were
analyzed for respiratory measurements. Indirect calorimetry
was used to calculate the carbohydrate (CHO) and lipid
oxidation (FAT), and total energy expenditure during the
match. We used stoichiometric equations and appropriate
caloric equivalents (Peronnet and Massicotte 1991), with the
assumption that the nitrogen excretion rate was 135 lg
kg
-1
min
-1
(Romijn et al. 1993). The equations were:
CHO rate oxidation (g min1Þ
¼ð4:585 _
VCO2Þð3:226 _
VO2Þ
Fat rate oxidation (g min1Þ¼ð1:695 _
VO2Þ
ð1:701 _
VCO2Þ:
Mass was expressed in grams per minute and gas
volume in liters per minute. _
VO2and _
VCO2values were
averaged every minute.
Total energy expenditure ¼½ð%CHO=100Þ _
VO2
5:05 kcal L1
þ½ð%Fat=100Þ _
VO2
4:7 kcal L1
The percentages of carbohydrates and lipid oxidations
were calculated by using the following equations:
%CHO ¼½ðRER 0:71Þ=0:29100
%Fat ¼½ð1RERÞ=0:29100:
Statistics
All the statistical analyses were completed using Statistica
5.5 software. Results are presented as their mean ±SD or
extreme values. ANOVA for repeated measurements and
Tukey post hoc tests were used to analyze the data.
Spearman correlation test was also used. Significance was
set at P\0.05.
Results
The PANAS gave a positive affect of 3.2 (2.3–4.3) and a
negative affect of 1.3 (1–1.8). The brief COPE showed an
active coping score of 3 (1–4), planning of 2.9 (1–4),
positive reframing of 2.8 (1.5–3.5), acceptance of 2.7
(1–4), self-distraction of 2.6 (1–4), using instrumental
support of 2.4 (1–4), middle level of humor of 2.2 (1–4),
using emotional support of 2.2 (1–4), self-blame of 2.1
(1.5–3), venting of 2 (1–3), low level of behavioral
disengagement of 1.3 (1–2.5), denial of 1.3 (1–3.5),
substance use of 1.3 (1–3), and religion of 1.2 (1–2).
We observed a significant increase in heart rate right at
the beginning of the contest and the rate stayed elevated
until the end of the game (Fig. 1). Significant increases
both in LF and in the LF/HF ratio (Fig. 1) and a significant
decrease in the mean R–R were also observed (Table 1).
No changes in HF and HF n.u. were found. The CO
2
release and the respiratory exchange ratio significantly
decreased during the game (Fig. 2). When calculating the
oxidation rate, lipid oxidation was found to significantly
increase, whereas glucose oxidation significantly decreased
(Fig. 2). At the 25 min time point, the two oxidation curves
crossed each other. No significant changes were noted in
_
VO2;EE, VF, Vt, and bF.
In addition, no significant correlation was found
between the outcome of the PANAS and brief COPE tests
and any of the physiological variables. All participants lost
their game and reported that their level of effort was sim-
ilar to a tiring, serious match. All of the data concerning
physiological variables before and during chess play are
presented in Table 1. The overall energy expenditure in our
Eur J Appl Physiol (2009) 105:343–349 345
123
players during the entire game was of 138 kcal (extreme
values 102–198 kcal).
Discussion
We have studied the effects of playing chess in chess
competitors (national and international level) on a series of
cardio-respiratory and metabolic variables.
The evaluation of our subjects through the PANAS and
the Brief COPE tests before the chess contest showed that
their basal amount of perceived stress was rather low and
they were psychologically healthy. Also, all of our subjects
reported that the contest was as challenging and tiring as a
regular match. Therefore, artifacts due to specific psycho-
logical state or trait do not seem to generate bias in the
stress-induced physiological responses of our subjects.
Before the beginning of the contest, the heart rate was
rather elevated. Such observations indicate that our par-
ticipants were reacting to the start of the game via
anticipatory mechanisms (Wirtz et al. 2006). At the start of
the game, both heart rate and RER slightly increased. Such
elevated levels could indicate that substrate oxidation
mainly involved carbohydrates. However, the transient
increase in RER may also reflect changes in respiratory
phenomena. Only a slight increase (not significant) in the
ventilation rate was observed at the beginning of the game.
In any case, this indicates that the players were very
reactive. Such changes are certainly under sympathetic
control, and may be related to unspecific stress responses
(Selye 1951). Many studies in humans have documented an
increase in SNS activation during mental stress (e.g. See-
matter et al. 2000; Garde et al. 2002). In fact, the heart rate
variability measurements in our participants at the begin-
ning of the game revealed a significant increase both in LF
and in the LF/HF ratio, a decrease in mean R–R and no
changes in HF, indicating an activation of the sympathetic
system (Montano et al. 1994; Pagani et al. 1991) with no
changes in the parasympathetic system (Hayano et al.
1991). It is well known that Vt and bF have a large impact
on the HRV indices, especially in the vagally mediated HF
spectral band (Hirsch and Bishop 1981). Both Vt and bF
were measured continuously during the study, and we did
not observe any significant changes in breathing pattern.
These results indicate that the changes in the spectral
component of the R–R intervals are due to increased
sympathetic stimulation rather than to changes in respira-
tion pattern or in vagal activation. During the game, we
initially observed stabilization in the heart rate, followed
by a significant increase through the end of the game.
During that time, the CO
2
release significantly decreased,
whereas oxygen consumption stayed stable. This led to a
significant decrease in the RER. One possible explanation
could again be hyperventilation, which could eventually
lead to a relative lowering in CO
2
production (hypocapnia)
related to O
2
consumption. However, no hyperventilation
Fig. 1 Indexes of sympathetic involvement before and during a chess
game: aHeart rate; bLF/HF ratio (number of subject =20);
*P\0.05. LF/HF Ratio between the low and high frequency band
Fig. 2 Indexes of substrate utilization before and during a chess
game: aRER; bCHO and FAT oxidation rate (%) (number of
subject =20); * P\0.05. RER Respiratory exchange ratio; CHO
carbohydrate oxidation rate; FAT lipid oxidation rate
346 Eur J Appl Physiol (2009) 105:343–349
123
was noticed during the course of our study. Therefore, a
significant increase in lipid oxidation and a dramatic
decrease in carbohydrate metabolism may have occurred
during the match.
At the end of the game, the oxidation of carbohydrates
was very low, and the participants were almost exclusively
oxidizing lipids. During the whole game, the total energy
expenditure remained constant, but was more elevated than
during resting time (Levine et al. 2000; Levine 2005).
However, we cannot exclude that we might have observed
a transient increase in carbohydrate consumption at the
beginning of the game and then a return to resting condi-
tion. During the game, the levels of LF and the LF/HF ratio
were elevated and were significantly higher than before the
start of the game. The HF level did not change during the
game. Therefore, the sympathetic system seems to be
stimulated during the course of the contest, with no chan-
ges in the parasympathetic system. However, it has
previously been demonstrated that brief exposure to psy-
chological stressors may lead to both an increase in LF and
in the LF/HF ratio with a reduction of the HF level,
indicating increased sympathetic activity along with with-
drawal of the parasympathetic system (e.g. Delaney and
Brodie 2000). Somehow, our results with respect to the
absence of any parasympathetic withdrawal during the
course of the game are at variance with those reported in
the literature. However, the nature of the stimulus was
different, and the mental workload might have been lower
in our study as our volunteers were well trained in handling
such stimuli. Furthermore, the interplay between the sym-
pathetic and vagal regulation of HR is not always
organized in a reciprocal fashion, wherein increased
activity in one system is accompanied by decreased activity
in the other. A simultaneous sympathetic and vagal acti-
vation has been observed during cold face immersion
(Tulppo et al. 2005), and also in other circumstances in
healthy subjects (Mourot et al. 2007). It is highly possible
that increased sympathetic activation occurs without any
change in vagal outflow during a demanding mental stress
situation without exercise or body position changes, as in
the present study.
All of our observations indicated that the chess players
were very stimulated during the game, but the nature of the
stimuli might have been different during the contest com-
pared to the stimuli that occurred before and at the
beginning of the game. Interestingly, the two oxidation
curves (lipid and carbohydrate) crossed each other 25 min
after the start of the contest. Such changes observed during
the game may reflect an adjusted response to the real
demands of the task. After the more acute response that
was observed right at the beginning of the game, the sub-
ject may have been adjusting to a longer lasting effort.
It is not clear why there could be a switch in substrate
oxidation during a lasting mental challenge. Numerous
studies have shown that different kinds of stressors
(examination, environmental stressors, and laboratory-
Table 1 Heart rate, gas and metabolic variations during the chess match in experienced chess players (n=20)
Parameters Units Before Beginning Middle End
HR beats min
-1
75 (60–101) 81 (59–108)* 79 (65–95) 86 (65–120)*
Mean R–R ms 877 (585–1,210) 819 (666–1,022)* 779 (639–930)* 766 (556–953)*
LF ln ms
2
6.3 (4.2–8.0) 6.7 (5.2–8.1)* 6.8 (4.9–8.2)* 6.6 (4.0–8.2)*
HF ln ms
2
5.7 (3.8–7.3) 6.1 (3.6–7.3) 5.8 (3.6–7.6) 5.7 (2.1–7.4)
HF n.u 33.5 (22–44.6) 32.3 (18.9–51.5) 30.8 (13.6–44.3) 31.4 (13.1–50.2)
LF/HF 1.3 (0.2–5.1) 2.4 (0.5–5.1)* 3.3 (0.8–8.1)* 3.0 (1.0–7.0)*
Vt ml min
-1
0.59 (0.40–0.79) 0.63 (0.44–0.82) 0.55 (0.38–0.80) 0.58 (0.43–0.80)
bF cycle min
-1
15.99 (10.97–20.40) 15.94 (10.86–22.20) 15.94 (10.50–21.40) 16.29 (10.70–22.30)
VF l min
-1
9.61 (6.87–13.38) 10.32 (6.62–13.55) 9.06 (5.95–13.15) 9.52 (5.59–13.30)
_
VO2ml min kg
-1
4.18 (2.36–6.71) 4.51 (2.59–5.80) 4.32 (2.78–5.89) 4.41 (2.59–6.34)
_
VCO2ml min kg
-1
3.57 (2.37–5.45) 3.94 (2.23–5.27) 3.04 (1.95–4.37)* 3.11 (1.72–4.65)*
RER 0.89 (0.79–1.03) 0.92 (0.81–1.07) 0.75 (0.67–0.81)* 0.74 (0.65–0.89)*
CHO g min
-1
0.22 (0.10–0.51) 0.27 (0.11–0.74) 0.01 (0.00–0.16)* 0.002 (0.00–0.32) *
FAT g min
-1
0.08 (0.04–0.21) 0.07 (0.02–0.15) 0.16 (0.09–0.22)* 0.16 (0.07–0.24) *
EE kcal min
-1
1.53 (1.14–2.00) 1.67 (1.18–2.20) 1.53 (1.17–2.01) 1.55 (1.14–2.04)
Results are expressed as mean and extreme values in brackets
HR Heart rate; Mean R–R mean values of heart rate variability; LF low frequency; HF high frequency; LF/HF ratio between the low and high
frequency band; _
VO2O
2
consumption; _
VCO2CO
2
production; RER respiratory exchange ratio; bF respiratory frequency; VF ventilatory flow; Vt
tidal volume; CHO carbohydrate oxidation rate; FAT lipid oxidation rate; EE energy expenditure
*P\0.05 compared to the data obtained before the contest
Eur J Appl Physiol (2009) 105:343–349 347
123
based stressors) may influence metabolism and the con-
centration of lipids in blood (Stoney et al. 1997,1999;
Niaura et al. 1992). However, not much is known con-
cerning the use of substrates during mental challenge.
Interestingly, similar kinds of adaptations have been
reported in exercise physiology. Moderate physical exer-
cise is generally associated with the preponderant
utilization of lipids, whereas acute and intensive physical
exercises are under carbohydrate metabolism. The shift in
substrate oxidation has been described as the ‘‘crossover
concept’’ and depends on the relative intensity of the
exercise and therefore on the endurance training of the
subjects (Brooks and Mercier 1994). Similarly, this may
apply to psychological stress physiology. However, to
validate such a psychological crossover concept, one
should be able to quantify the intensity of psychological
stress and relate it to substrate oxidation. Another inter-
esting feature in this context is that training (endurance
training?) of the subject could influence substrate oxidation
during a mental challenge. One could therefore speculate
that specific training could be designed for chess players.
However, to validate such a new approach, further inves-
tigations are required.
In summary, we herein described an interesting real-life
stressor that seems to be a useful stress model in that it
had significant effects on heart rate variability and
metabolism.
Acknowledgments The study was partly supported by the Chess
League of Limousin, France. The authors are very grateful for the
volunteers who were all very excited to participate and the League of
Limousin that encouraged this research. The Conseil Ge
´ne
´ral de la
Vienne is also thanked for inspiring our collaboration with research
laboratories of the Oulu region (Finland) and for giving a traveling
grant (BD).
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