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The neuroscience of exercise is a growing research area that is dedicated to furthering our understanding of the effects that exercise has on mental health and athletic performance. The present study examined three specific topics: (1) the relationship between exercise and mental disorders (e.g. major depressive disorder, dementia and Parkinson's disease), (2) the effects of exercise on the mood and mental health of athletes, and (3) the possible neurobiological mechanisms that mediate the effects of exercise. Positive responses to regular physical exercise, such as enhanced functional capacity, increased autonomy and improved self-esteem, are frequently described in the recent literature, and these responses are all good reasons for recommending regular exercise. In addition, physical exercise may improve both mood and adherence to an exercise program in healthy individuals and might modulate both the performance and mental health of athletes. Exercise is associated with the increased synthesis and release of both neurotransmitters and neurotrophic factors, and these increases may be associated with neurogenesis, angiogenesis and neuroplasticity. This review is a call-to-action that urges researchers to consider the importance of understanding the neuroscience of physical exercise and its contributions to sports science.
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Review
Neuropsychobiology 2013;68:1–14
DOI: 10.1159/000350946
Neuroscience of Exercise:
FromNeurobiology Mechanisms
toMentalHealth
EduardoMattaMelloPortugal
a–c
ThaisCevada
a,d
RenatoSobralMonteiro-Junior
a,b,e
ThiagoTeixeiraGuimarães
a
ErcoledaCruzRubini
a,e,h,i
EduardoLattari
a,b
CharleneBlois
a,f,g
AndreaCamazDeslandes
a,b
a
Neuroscience Laboratory of Exercise, UGF,
b
Exercise and Sport Sciences Graduate Program, Gama Filho University,UGF,
c
Performance Research Group, UGF,
d
Institute of Psychiatry of the Federal University of Rio de Janeiro, IPUB/UFRJ,
e
ClinicSchool of Physiotherapy, UGF,
f
Federal University of Rio de Janeiro, UFRJ,
g
Biometry Laboratory, Federal University
of Rio de Janeiro, UFRJ,
h
Physical Education Course, University Estácio de Sá, and
i
Laboratory of Physical Activity and Health
Promotion, LABSAU/UERJ, Rio de Janeiro , Brazil
mental health of athletes. Exercise is associated with the in-
creased synthesis and release of both neurotransmitters and
neurotrophic factors, and these increases may be associat-
ed with neurogenesis, angiogenesis and neuroplasticity.
This review is a call-to-action that urges researchers to con-
sider the importance of understanding the neuroscience of
physical exercise and its contributions to sports science.
Copyright © 2013 S. Karger AG, Basel
Men ought to know that from nothing else
but the brain come joys, delights, laughter and
sports, grief, despondency, and lamentation.
Hippocrates , 400 BC
Introduction
Neuroscience is a growing research area comprising a
variety of multidisciplinary investigations that seek to un-
derstand the relationship between the body and the brain.
At the beginning of the previous century, our knowledge
of the correlation between neuroscience and exercise was
Key Words
Neurobiology of exercise · Depression · Adherence ·
Physical training · Mood
Abstract
The neuroscience of exercise is a growing research area
thatis dedicated to furthering our understanding of the ef-
fects that exercise has on mental health and athletic perfor-
mance. The present study examined three specific topics:
(1)the relationship between exercise and mental disorders
(e.g. major depressive disorder, dementia and Parkinson’s
disease), (2) the effects of exercise on the mood and mental
health of athletes, and (3) the possible neurobiological
mechanisms that mediate the effects of exercise. Positive re-
sponses to regular physical exercise, such as enhanced func-
tional capacity, increased autonomy and improved self-es-
teem, are frequently described in the recent literature, and
these responses are all good reasons for recommending reg-
ular exercise. In addition, physical exercise may improve
both mood and adherence to an exercise program in healthy
individuals and might modulate both the performance and
Received: September 28, 2012
Accepted after revision: March 24, 2013
Published online: June 15, 2013
Eduardo Matta Mello Portugal, MSc
Programa de Pós Graduação Stricto Sensu em Ciências do Exercício e do
Esporte da Universidade Gama Filho, Rua Manoel Vitorino 553
Piedade, Rio de Janeiro, RJ 20748-900 (Brazil)
E-Mail portugalemm
@ yahoo.com.br
© 2013 S. Karger AG, Basel
0302–282X/13/0681–0001$38.00/0
www.karger.com/nps
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Neuropsychobiology 2013;68:1–14
DOI: 10.1159/000350946
2
acquired primarily through studies that investigated the
effects of certain substances (e.g. ammonia) and the he-
modynamic responses to them on brain function and fa-
tigue [1, 2] . The effects of physical exercise on the struc-
tures and functions (i.e. physiological, psychological and
biochemical) of the central nervous system (CNS) have
received increasing attention from the scientific commu-
nity, in the context of both the potential mental health
benefits for clinical populations and potential sports sci-
ence applications, and these effects have been examined in
studies of the exercise adherence, mental health and ath-
lete performance
[3–6] . For example, Pires [3] has shown
that there is a growing number of citations for studies that
investigate the central governor model and exercise.
Studies of the efficacy of using exercise to treat and/or
prevent mental disorders are essential, particularly given
the fast-growing elderly population and the consequent rise
in the prevalence of neurodegenerative illnesses and de-
pression. Recent increases in the incidences of several men-
tal disorders, such as major depressive disorder (MDD)
[7] ,dementia [8] and Parkinsons disease (PD) [9] , high-
light the necessity of increasing research efforts that focus
on identifying treatments that can improve an individuals
mental health. Although pharmacological therapy is the
current gold standard for the treatment of all mental dis-
eases, the possible adverse effects of medication contribute
to failures in patient compliance. Therefore, both reducing
the costs of medications and hospitalizations and enhanc-
ing the quality of life of mental health patients should be
prioritized. A recent review published by members of our
laboratory showed that regular exercise reduces the symp-
toms of MDD, dementia and PD
[5] . Thus, exercise can be
an adjuvant treatment for several mental diseases. One pos-
sible neurobiological mechanism underlying the positive
effects of exercise is the increased synthesis and release of
neurotransmitters and neurotrophins, which could result
in neurogenesis, angiogenesis and neuroplasticity
[10] .
Nonetheless, more information regarding the neurological
effects of exercise in a clinical sample is needed.
Even though there is strong evidence that exercise has
positive effects on mental health and cognition, these out-
comes are dependent on regular exercise practice
[11] .
The high rates of physical inactivity make it difficult to
achieve the benefits of exercise
[12] . In this context, Wil-
liams et al.
[13] have found that the acute affective re-
sponse to exercise is an important determinant of exercise
adherence via cognitive (i.e. perceived autonomy and
self-efficacy) and interoceptive (i.e. lactate accumulation
and blood pH) pathways. Therefore, given the modula-
tion of adherence by the acute affective response to exer-
cise, which is dependent on the exercise setting, the opti-
mal prescription should be determined.
Although regular exercise has the potential to promote
mental health, an excessive level of exercise can have ad-
verse effects, such as overtraining
[14] . In addition to exer-
cise, other factors associated with a high level of pressure
to perform well and other stressors, contribute to the high
prevalence of mental disorders among elite athletes
[15] .
Pharmacological treatment is well accepted for the treat-
ment of athletes
[16] , although other strategies, such as in-
creased energy intake and decreased energy expenditure,
are also necessary
[17] . Thus, the control of psychological
variables, combined with physiological variables, is essen-
tial to the success of an athlete. Corroborating this argu-
ment, Noakes
[4] argues that during endurance events,
structures in the CNS have an important function in deter-
mining the strategies that are used to limit exercise efforts
and preserve the health of the athlete, and these structures
play a role in the modulation of other body systems during
exercise, ultimately contributing to improved performance.
Considering the importance of knowledge about the re-
lationship between exercise and the broad context of neu-
roscience involved in mental health, along with adherence
to exercise programs, performance and the diversity of the
variables analyzed in these studies, we conducted a com-
prehensive review to identify the current state of the art in
the field of the neuroscience of exercise. Thus, the effects
of exercise on physiological, psychological and biochemi-
cal variables related to CNS structure and function were
analyzed. Our study began by examining the relationships
between exercise and the most prevalent mood disorders
and neurodegenerative diseases. However, it is also worth
discussing the acute effects that exercise has on mood and
adherence to an exercise program. Moreover, what pro-
tects the mind does not always protect the body; diagnoses
of various mental disorders are surprisingly common
among athletes who have been subjected to overtraining,
fatigue, competition-related stress, injuries, failure and re-
tirement. Thus, the brain may contribute to diminished
performance or increased fatigue in some circumstances.
The final section of this article examines a neurobiological
hypothesis that may explain the mechanisms that underlie
the effects of exercise on mental health.
Mental Disorders and Neurodegenerative Disorders
Major Depressive Disorder
Data from the World Health Organization [18] provide
evidence of a causal relationship between MDD and the
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3
subsequent development of a disability, and some diseas-
es that have MDD as a comorbidity are associated with a
diminished Mean Health Score
[18] . There is a relation-
ship among morbidity due to this disease, aging, the num-
ber of systemic illnesses and a lack of physical exercise
[7] .
Several hypotheses regarding the mechanisms that un-
derlie the pathophysiology of MDD have been studied.
The most popular theory involves the activity of mono-
amines, namely reductions in the activities of serotonin
and norepinephrine
[19] . Another mechanism involved
in depression is the hyperactivity of the hypothalamic-
pituitary-adrenal axis due to the increased release of cor-
tisol and corticotropin-releasing factor
[20] .
The effect of exercise, as an adjunct to pharmacologi-
cal treatment, on depressive symptoms has been studied
[5, 21] . Follow-up studies, clinical trials and randomized
controlled trials have found evidence of a positive corre-
lation between regular physical exercise and a reduction
in depressive symptoms
[21–25] . Both strength training
and aerobic training have positive effects in the treatment
of depression
[25] . Furthermore, high-intensity strength
training (80% of one maximum workload lifted (1 repeti-
tion maximum (RM))
[23] , moderate aerobic training
(17kcal/kg/min)
[22] and supervised moderate-intensity
training (70–80% HRR)
[21] were all shown to induce
positive responses in an investigation of the effect of ex-
ercise on depressive symptoms. In contrast, Krogh et al.
[26] have observed the opposite pattern of results in a re-
cent meta-analysis. They concluded that exercise has
small short-term effects on the severity of depressive
symptoms but that the existing data regarding the long-
term effects of exercise are inconclusive. The lack of in-
clusion criteria, even for studies of good quality, can ex-
plain these results. Using rigorous inclusion criteria, our
group performed a meta-analysis
[25] that showed that
both aerobic exercise and strength training have positive
effects on depressive symptoms. These effects are sub-
stantial in elderly individuals and individuals who have
mild depressive symptoms
[25] .
It appears that the efficacy of using exercise to reduce
the severity of depressive symptoms depends on the level
of adherence to an optimal exercise regimen; a combina-
tion of moderate-intensity aerobic training and high-inten-
sity strength training may provide more positive benefits
than other exercise programs. Neurobiological mecha-
nisms can explain these positive effects (see the Neurobiol-
ogy of Exercise section). However, there are both method-
ological limitations (i.e. lack of statistically significant
results, poor sample selection criterion and MDD diagnos-
tics,no adequate control of exercise regimen) that limit our
understanding of this observation. In summary, more re-
search is necessary to better understand the effects of exer-
cise on the depressive symptoms of MDD patients.
D e m e n t i a
Dementia is the most prevalent neurodegenerative
disease worldwide. In a review study it was estimated that
24.3 million cases have been reported, and 4.6 million
new cases are reported annually in the world
[27] . Despite
the heterogeneity of its symptoms, dementia is associated
with the progressive loss of various cognitive functions
and the consequent impairment of an individual’s ability
to perform daily life activities. Mental stimulation, prop-
er nutrition and exercise appear to exert both prophylac-
tic and therapeutic effects on the development and pro-
gression of neurodegenerative dementia
[28–30] . Physi-
cal activity alone is associated with a 28% reduction in an
individual’s risk of developing the disease
[31] .
Given the possible adverse effects related to pharma-
cological treatment, the quality of life and the general
well-being of individuals who suffer from dementia can
be compromised
[32] . Thus, it is important to investigate
alternative, non-pharmacological treatment strategies
such as exercise
[33] . A meta-analysis conducted by Hein
et al.
[32] found that regular exercise performed with the
mean training duration from all studies of 23 weeks, with
a range of 2–112 weeks, had positive effects on both cog-
nitive and behavioral improvement. There was an aver-
age of 3.6 sessions per week, ranging from 1 to 6 sessions,
with each session lasting an average of 45 min (mean) and
ranging from 20 to 150 min. However, Forbes et al.
[34]
conclude that there is not sufficient evidence to deter-
mine whether participation in a regular exercise program
actually benefits people with dementia. The inconclusive
results of their study may have been obtained because
these authors chose criteria for assessing the methodolog-
ical quality of existing studies that resulted in the inclu-
sion of only two studies in their meta-analysis.
There is some evidence that exercise can improve cog-
nitive function, the ability to perform daily life activities
and the ability to walk in dementia patients, but both the
low intensities of the prescribed exercise regimens that
were used in the studies that Forbes et al.
[34] reviewed and
the methodological qualities of those studies can be criti-
cized. For example, a recent study examined 62 dementia
patients who underwent 3 months of progressive resis-
tance and functional group training. The resistance train-
ing targeted functionally relevant muscle groups at a sub-
maximal intensity (70–80% of 1RM) and was performed in
groups of 4–6 participants for 3 months (2 h, twice a week).
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This study found evidence of increases in both the strength
and functional capacities of the treated patients that were
not observed among the patients in the control group
[35] .
Alzheimer’s disease (AD) is the most prevalent form
of dementia and is associated with the accumulation of
senile plaques and neurofibrillary tangles that result in
the atrophy of the hippocampus. Data from animal mod-
els suggest that in the animal strains that have been stud-
ied, physical exercise is associated with a reduction in the
formation of β-amyloid deposits and the enhanced clear-
ance of these deposits. β-Amyloid is a principal compo-
nent of the senile plaques that accumulate in the brains of
AD patients, and exercise has also been shown to amelio-
rate the accumulation of the phosphorylated form of the
τ protein, which is essential for the formation of neurofi-
brillary tangles. In addition, physical activity appears to
promote mechanisms of neuronal resilience that reduce
inflammation in the CNS
[36] .
Previous studies have shown that regular participation
in a physical activity, such as strength training, aerobics
or walking, strength, flexibility, balance and aerobic train-
ing, or a combination of these exercises for 16 weeks or 1
year is able to improve some parameters related to health
[5] . The quality of life in AD patients can be improved by
increasing their strength and balance, thus reducing their
risk of falling and increasing the facility with which they
are able to perform daily life activities
[5] .
Because of the importance that exercise appears to
have in improving the lives of AD patients, randomized
controlled trials that investigate the effects of exercise on
the synthesis and release of neurotrophic factors, neu-
rotransmitters, hormones and other physiological mark-
ers are still needed, as are studies that use more precise
methods of measuring these effects.
Parkinsons Disease
PD is the second most prevalent neurodegenerative dis-
ease among elderly individuals, and it generally affects men
more often than it affects women
[37] . The disease is char-
acterized by the loss of dopaminergic neurons in the sub-
stantia nigra, and it is associated with diminished mito-
chondrial activity that results in an increased production
ofreactive oxygen species (ROS)
[38] . The cardinal symp-
toms of PD are hypokinesia, tremors, postural imbalances
and gait deficits. Pathological signs are most common
among individuals who are between the ages of 50 and 60
[39] , but symptoms may appear during a number of stages
of life. In addition to the aforementioned motor impair-
ments, behavioral, cognitive and other functional changes
can be observed at different stages of PD. Although drug
treatment is the most widely used method of treating PD,
recent studies have shown that exercise and pharmacologi-
cal therapy are important interventions to improve motor
control, autonomy and awareness of the patients day-to-
day quality of life
[40] . In addition, individuals who have
higher fitness levels have a 33% lower risk (RR = 0.67) of
developing PD
[41] . Participating in an exercise program
that involves activities with moderate-to-vigorous intensity
during middle age appears to have a neuroprotective effect
of as high as 38% (RR = 0.62) for individuals who are not
affected by the disease
[41] . Given the relatively low cost of
engaging an individual in a physical training program and
the various benefits that can be achieved by doing so, exer-
cise should be given special attention as a possible means of
protecting against or reducing the effects of this disease.
The evidence for the effectiveness of exercise in ame-
liorating the symptoms of PD has been favorable, but it
remains limited in scope. Both aerobic exercise (between
40 and 60% HRres, 3–4 times per week, 30 min per ses-
sion) and strength training (2–3 times per week, 40–80%
of 1RM)appear to result in improved motor function in
PD patients
[42] ; these types of exercise also appear to
improve the quality of life in individuals with PD
[43, 44] .
However, strength training appears to be of greater ben-
efit to patients with the disease. Bloomer et al.
[45] have
assessed the impact of an exercise program on the activi-
ties of some oxidative factors (C
3
H
4
O
2
and H
2
O
2
). Indi-
viduals engaged in resistance training twice per week for
a period of 8 weeks (3 sets, 5–8 reps, until momentary
muscular failure). Although these authors did not iden-
tify any significant between-group differences in the ac-
tivities of the antioxidant enzymes that were analyzed,
thegroup that had engaged in resistance training showed
significant (15–16%) reductions in the serum levels of
various biomarkers of oxidative stress, whereas members
of the control group showed 14% increases in the serum
levels of these markers. Importantly, this reduction oc-
curred after a relatively short period of training (8 weeks)
with a low frequency (twice per week).
This result suggests that the positive physiological ef-
fects of strength training are rapid and indicates that there
may be an optimal dose-response relationship. Moreover,
PD patients who participated in exercise programs that
included both high-intensity strength training (60–80%
4RM) and balance training showed improved abilities
to control the stability of their bodies and were able to
maintain the same level of performance over a period of
1monthafter the conclusion of their training program
[46] . These findings support the hypothesis that the effects
of this type of training program remain stable even after a
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5
period during which a PD patient does not participate in
regular training. These improvements may be related to
neurobiological changes that occur as a result of physical
exercise, particularly neurogenesis [47] , an increase in mi-
tochondrial activity and an increase in the synthesis of cer-
tain neurotransmitters, such as dopamine
[48] . The neu-
robiological mechanisms of the effects of exercise are dis-
cussed in detail in the Neurobiology of Exercise section.
Currently, there are several practical considerations
that must be considered when determining the appropri-
ate exercise regimen for PD patients. Data from the recent
literature recommend aerobic activities using a cycle er-
gometer and body support that are performed 3–5 times
per week at a level of intensity (low, moderate or high)
determined on the basis of the trainability and disease
stage of each patient. The levels of intensity are character-
ized as follows: an intensity <40% of the heart rate reserve
(HRR) or VO
2
reserve (VO
2
R) is considered low; an in-
tensity <60% of the HRR or VO
2
R is considered moder-
ate, and an intensity >60% HRR or VO
2
R is considered
high. The recommendations for strength training for PD
patients prioritize strengthening the lower limbs and sug-
gest strength training 2–3 times per week at an intensity
of 40–50% 1RM (light) or 60–80% 1RM (moderate/high)
depending on the aforementioned conditions regarding
the disease stage and trainability of each patient. The lit-
erature also suggests that both aerobic and strength train-
ing should be accompanied by functional exercises, espe-
cially exercises involving gait ( fig.1 )
[49] .
Mood and Anxiety: Acute Effects of Exercise,
Adherence to an Exercise Program, and Athletic
Performance
Effects of Aerobic Exercise
There are many scientific studies that provide evidence
of the beneficial effects of exercise on disease prevention
and overall health. However, promoting adherence to
programs of regular physical activity is one of the greatest
challenges in the field of sports science. The affective re-
sponse that a single exercise session provokes has been
shown to predict the level of engagement of a participant
over the course of the subsequent 6–12 months
[13] . The
link between affective responses and adherence has been
explained by Williams using an integrative model [for a
review, see
6] . Thus, it is likely that improving our under-
standing of the effects that different types of exercise have
on human behavior may also improve our ability to in-
crease the rates of adherence to exercise programs.
According to Ekkekakis and Petruzzello [50] , there
may be a U-shaped relationship between aerobic exercise
intensity and affective state. This theory suggests that the
optimal intensity, the one that produces the most positive
affective response, would be a moderate intensity that is
near the ventilatory threshold ( 65% VO
2max
[51] ). It
may be that intensities above the ventilatory threshold
are perceived as threatening by most individuals and,
therefore, tend to generate a negative affective state
[52] .
Moreover, although intensities below the ventilatory
threshold have a high individual variability, these lower
intensities are perceived as pleasurable by most individu-
als
[52, 53] . A meta-analysis conducted by Reed and Ones
[54] showed that low-intensity exercises that had a dura-
tion of 35 min or less also induced a strong activation of
positive affect. In contrast, recent research has shown that
an exercise protocol that included intervals of high-inten-
sity generated more pleasure than a program that used a
continuous moderate intensity
[55] . There is also evi-
dence that suggests that positive behavioral outcomes
tend to occur after exercising at a self-selected intensity
[56] .
It appears that moderate-intensity exercise programs
result in improved behavioral, affective, mood or anxiety
responses
[53] . The response to this type of exercise regi-
men represents a common point between two classical
models of exercise efficacy that have been proposed in the
literature (the inverted U-shaped curve and circumplex
models of affect), both of which are presented in figure 2 .
The circumplex model consists of a two-dimensional
structure in which combinations of arousal and affective
valence are represented in quadrants [for a review, see
57 ].
The substantial variation in the findings of studies of
exercise efficacy may be attributed to the use of different
methods of measuring behavior and to the failure to stan-
dardize the pretest scores in addition to the effects that
depend on an individual’s level of physical fitness. For
example, affective state, mood and anxiety are often treat-
ed as synonyms, but there are differences in the opera-
tional definitions of these terms that could theoretically
result in differing interpretations when comparing the re-
sults. Thus, it appears that the variable that is termed ad-
herence to an exercise program is the most consistently
applied measure of affective state in this context
[13] .
Effects of Strength Training
Despite the increasing interest in the acute effects of
exercise on affect, mood and anxiety, few studies have at-
tempted to investigate the differential influences of vari-
ous types of exercise. For example, the effects of strength
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training are rarely compared with the effects of aerobic
exercise
[58] .
The results of studies of the acute effects of strength
training on mood have been contradictory, and studies
that have focused on low- and high-intensity strength
training programs have had divergent results
[58] . Fur-
thermore, the time between the conclusion of an exercise
session and the time at which the mental state of the par-
ticipant is evaluated appears to influence the observa-
tions that are obtained. It appears that a minimum recov-
ery time of 20 min must elapse before a decrease in the
anxiety level of a participant can be observed, and par-
ticipants require a 40-min recovery period before a re-
duction in their levels of physical exertion can be dis-
cerned
[59, 60] . When different types of physical exercise
are compared, both strength training and aerobic exer-
Alzheimer Major depressionParkinson
DiseaseConsequencesPhysiopathologyBenefitsExercise
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Fig. 1. Effects of exercise on neurodegenerative diseases and men-
tal disorders. The reductions in dopamine and mitochondrial
function, the generation of β-amyloid plaques and hippocampal
atrophy and the decreases in the serotonin and noradrenaline lev-
els (in the hippocampus, hypothalamus, amygdala, cortex and oth-
er parts of brain) are the primary alterations that result in PD, AD
and MDD, respectively. Exercise training could be beneficial be-
cause neurotransmitters and neurotrophic factors are synthesized
in response to physical exertion. These factors could delay of the
progression of neurodegenerative diseases and mental disorders.
Moreover, exercise improves physical function and functional au-
tonomy. ADLs = Activities of daily living.
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cise appear to promote poorer moods among partici-
pants who are surveyed immediately after an exercise
session; however, there is a tendency for improvement in
the moods of the participants after 30 min of recovery
[61] . The recovery interval between the sets within a
strength training session may be another variable that
influences the mood responses of participants. A long
recovery interval (3 min between two sets of exercises)
may result in an increased positive affect, whereas a short
interval (1 min) could instead result in increased anxiety
[60] . Interestingly, Bellezza et al. [62] showed that posi-
tive affective responses in women were more likely to
occur when small muscle groups were exercised at the
beginning of an exercise session.
Thus, it appears that there is no consensus regarding
which of the aforementioned acute variables that can be
incorporated into a strength-training program has the
most profound impact on mood.
Brain and Sports
In general, the literature shows that physical exercise
has favorable effects on mental health. Surprisingly, pop-
ulations that are composed of athletes may be subject to
specific exercise-related physical and mental stresses that
favor the emergence of mood and anxiety disorders
[16] .
Although sports psychiatry has been poorly studied to
date, investigations in this field should be emphasized be-
cause exercise-induced changes in an athlete’s behavior
and mental health may affect his/her performance in both
individual and team sports
[63] . In conjunction with
these considerations, studies of the neuroscience of exer-
cise and sports aim to investigate the effects of central
changes (neurophysiological and psychological) on ath-
letic performance and mental health
[64, 65] .
The mental health of an athlete is related to his/her abil-
ity to control emotions, manage stress and cope with inju-
ries, the excesses training and competitions. Top athletes
constantly experience stress and emotional overload be-
cause success is always associated with results and achieve-
ments. The physical and emotional stresses cause athletes
to constantly live on the edge psychologically. Conse-
quently, symptoms such as low motivation, sadness, de-
pressed mood, anger, decreased self-esteem, loss of iden-
tity, loss of self-confidence and even depression and sui-
cidal ideation become common in this population
[15, 16] .
Unfortunately, the prevalence of certain behaviors or men-
tal states (e.g. high levels of anxiety, attention deficit, hy-
peractivity and suicidal thoughts) that are risk factors for
mental illness (including overtraining syndrome, psycho-
sis, bipolar disorders and anxiety) are rarely studied.
In addition, a complex pattern of neurophysiological
factors (mood, pain tolerance and previous experiences),
neurobiological changes (cerebral metabolic changes,
substrate depletion, alterations in regional neurotrans-
mitter levels and cerebral temperature), central com-
mand activation (sense of effort) and peripheral factors
(afferents signals and the cardiopulmonary system) may
compromise the performance of an athlete by inducing
fatigue signals. Fatigue is characterized by an inability to
continue to execute a particular task, and the onset or se-
verity of fatigue may depend on the type, intensity and/or
duration of a particular task
[66] . Fatigue may be consid-
ered an increased difficulty in maintaining a given exer-
cise intensity and can be assessed with ratings of per-
ceived exertion (RPE), for example by the Borg scale
[67] .
A recent study investigated interventions related to tem-
perature and cerebral oxygenation, and these variables
are suggested to be trigger points and important determi-
nants for the development of central fatigue
[68–71] . The
temperature of the brain is determined by the balance be-
tween the heat produced by cerebral energy turnover and
the heat that is removed, primarily by cerebral blood flow
(CBF). The level of convection of heat between tissue and
0–2.0–4.0–6.0 2.0 4.0 6.0
(–) Valence (FS) (+)
(–) Activation (FAS) (+)
6.0
5.0
4.0
3.0
2.0
1.0
HI
MI
LI
Fig. 2. Kinetics of the affective response to exercise in the circum-
plex model: Two theories (inverted-U and inverted-J) suggest the
same optimal point (MI). The lines represent the inverted-U and
inverted-J forms, which are modulated by the light intensity (LI),
moderate intensity (MI), and high intensity (HI) of the exercise.
The gray area represents the positive affect activation that could
promote well-being and adherence to an exercise program.
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capillaries is considered to be very high [72] . The global
CBF is influenced by the partial pressure of CO
2
in the
blood (PaCO
2
). During low- and moderate-intensity ex-
ercise, the PaCO
2
and CBF remain unchanged from the
level at rest (50–55 ml/100 g/mm), and during high-in-
tensity exercise, hyperventilation occurs and the PaCO
2
decreases, resulting in vasoconstriction of the cerebral ar-
terioles and a consequent decrease in CBF
[66] . During
prolonged exercise, hyperthermia causes the global CBF
to decrease by 20%
[68] . The preservation of the auto-
regulatory activity of the brain depends on the ability to
increase and maintain sufficient cardiac output because
reduced blood pressure and cardiac output induce pe-
ripheral and brain vasoconstriction
[73] .
Under normal conditions, the decrease in PaCO
2
due
to high-intensity exercise does not restrict the supply of
oxygen to the brain; this mechanism is offset by the poor
perfusion of oxygen. However, when exercise is per-
formed in extreme conditions, such as at high altitude,
under conditions of dehydration or at high temperatures,
the oxygen supply decreases and there is no restriction of
cerebral metabolism, consequently leading to neurologi-
cal deficits
[74] . Thus, the occurrence of hyperthermia-
induced fatigue is supported by the observation that ex-
ercise in hot conditions reduces the voluntary activation
of motor neurons during a sustained maximal muscle
contraction
[75] . The reduced work capacity may be re-
lated to more than one factor, but exhaustion during pro-
longed exercise in the heat seems to coincide with the at-
tainmentof a critical internal temperature
[76, 77] . How-
ever, there is evidence contradicting this mechanism.
Girard et al.
[78] investigated the effect of hot conditions
on repeated sprint cycling performance and did not ob-
serve any effect on the pattern or extent of isometric knee
extensor fatigue following repeated cycling sprints in the
absence of hyperthermia.
In general, the neurobiological changes that are related
to fatigue include metabolic changes in the brain, particu-
larly changes in the levels of serotonin, dopamine and nor-
epinephrine. For example, high levels of serotonin are as-
sociated with negative behaviors, lethargy and sleepiness
[79] . One possible mechanism for these effects described
in the literature is competition between tryptophan and
free fatty acids for binding sites on the albumin protein
[79] . Both physical and mental exhaustion may be related
to dopamine deficiencies in specific brain areas such as the
ventral tegmental area of the midbrain, the substantial
nigra pars compacta and the infundibular nucleus of the
hypothalamus. Dopamine deficiencies in these brain areas
in conjunction with exhaustion support the hypothesis
that low levels of dopamine could reduce motivation and
motor coordination and could lead to lethargy and fatigue
[71] . Norepinephrine is related to a heightened state of
arousal (e.g. alertness) and activation of the adrenal me-
dulla, which stimulates cardiovascular responses, blood
perfusion and energy supply [80] . A recent study found
that compounds with central action, such as dopamine,
norepinephrine and glucose, best predict the rate of in-
crease in the RPE during constant exercise sets at different
intensities
[81] . The RPE seems to be additionally influ-
enced by brain activity and cognitive processes such as
emotion, motivation and memory
[82] . Therefore, in ex-
ercises with a constant load, the RPE becomes a good tool
for predicting the remaining time until fatigue. The linear
increase in the RPE observed in the study of Pires et al.
[81] was independent of the intensity of the exercise. One
possible mechanism could be the progressive and contin-
uous accumulation of metabolites in the periphery
[83] .
The metabolic variables (pH and the lactate, catechol-
amine, glucose and potassium concentrations) were re-
sponsible for a greater variation in the slope of the RPE in
both moderate intensity exercise and high-intensity exer-
cise
[81] . This same study also showed that metabolic vari-
ables combined with cardiopulmonary variables (heart
rate and breathing) may satisfactorily predict the time to
exhaustion for both moderate- and high-intensity exer-
cise. Therefore, based on these results, it becomes possible
to assume that the high level of cerebral blood glucose
coupled with the availability of dopamine as the exercise
progressed could have led to an increase in brain activity,
which may in turn have influenced RPE
[81] .
During prolonged exercise or when an individual is
operating with depleted energy reserves, the catabolism
of amino acids occurs, and the production/removal of
ammonia becomes another fatigue-related concern. The
accumulation of ammonium ions in astrocytes may cause
neurotoxicity and impaired cerebral circulation. The
presence of ammonia also affects the levels of various
neurotransmitters (glutamate, glutamine and GABA),
and it encourages the release of factors associated with
infection (primarily interleukins such as IL-6)
[84] that
are also related to mood and fatigue. A considerable de-
crease in the ratio of the cerebral rates of oxygen and car-
bohydrate metabolism may occur during vigorous exer-
cise, and the diminished supply of oxygen could cause a
major disruption in cerebral metabolism that results in
hyperventilation and hypocapnia
[85] .
Another condition that occurs in some athletes is over-
training. Overtraining appears to be a maladaptive re-
sponse to excessive exercise without adequate rest, result-
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9
ing in perturbations to multiple body systems (neurolog-
ical, endocrine and immune systems) coupled with mood
changes
[86] . The symptoms of overtraining include de-
pressed mood, general apathy, decreased self-esteem,
emotional instability, impaired performance, restless-
ness, irritability, disturbed sleep, weight loss, loss of ap-
petite, increased resting heart rate, increased vulnerabil-
ity to injuries, hormonal changes and a lack of supercom-
pensation
[87] . Armstrong and VanHeest [14] showed
that 60% of long-distance runners experienced symptoms
of overtraining at some point during their careers, 50% of
professional soccer players experienced these symptoms
during a single competitive season (5 months), and 33%
of basketball players experienced these symptoms during
their 6-week training period. For most athletes, the rela-
tionship between psychological stress, anxiety and ath-
letic performance is best understood via a self-regulation
model that consists in training regulation by emotional
status
[88] .
In sports, factors such as concentration, emotional
control and coping strategies are linked to better perfor-
mance
[63, 88] . The relationship between psychological
stress, anxiety and performance in sports is better demon-
strated by the individual zones of optimal functioning
(IZOF) as proposed by Hanin
[89] , providing a function-
al explanation for the dynamics of the emotion-perfor-
mance relationship based on a detailed description of ath-
letes’ idiosyncratic subjective experiences
[90] . In addi-
tion, the model suggests that self-emotional regulation by
athletes is an important tool during competitions
[88] .
Another physiological mechanism widely discussed is the
central governor model (CGM) proposed by Noakes et al.
[91] . The CGM shows that all types of exercise are regu-
lated by the CNS. The CNS is subconsciously capable of
managing neuromuscular recruitment and calculating the
metabolic cost to execute a task and succeed. Therefore,
the CNS’s anticipatory control should prevent the cata-
strophic failure of the human body
[91] . The implementa-
tion of a new approach to exercise science, after this para-
digm shift between peripheral control and central control
proposed by Noakes
[92] , is highly criticized [93–95] .
However, according to Pires
[3] , the science community
has almost accepted this theory. This author suggests that
these old concepts have new interpretations and that oth-
er aspects, such as the number of citations and the increas-
ing debate related to CGM, should be considered evidence
of the acceptance of this new theory in exercise science.
From these new ideas arise the crises that promote scien-
tific revolutions, and the exercise science follows a pattern
similar to the kuhnian model of scientific discovery
[3] .
In summary, the need for a comprehensive and inte-
grated multidisciplinary approach to understanding the
effects of central changes on athletic performance and the
mental health of athletes is evident from the results pre-
sented in the existing literature.
N e u r o b i o l o g y o f E x e r c i s e
Acute Exercise Mechanisms
There is evidence that physical exercise promotes
changes in the human brain due to increases in metabo-
lism, oxygenation and blood flow in the brain. Unfortu-
nately, our knowledge of how the human brain is affected
by physical exercise interventions is limited, and the avail-
able evidence is predominantly from animal studies
[5, 10] .
Studies with animals have shown that physical exercise
modulates the major CNS neurotransmitters that are as-
sociated with an individual’s state of alertness (norepi-
nephrine), the pleasure and reward system (dopamine)
and the level of anxiety (serotonin). Moreover, changes in
the levels of these neurotransmitters may have different
consequences depending on the type(s) of receptors and
the cortical areas that are activated
[96] . Other neurochem-
ical factors that may be released during physical activities
include opioids and endocannabinoids, which promote a
sense of euphoria and well-being, anxiolytic effects, seda-
tion and decreased sensitivity to pain in humans
[97] .
Other neuromodulators that are activated by acute ex-
ercise are trophic factors. Studies in animals have shown
that the expression levels of brain-derived neurotrophic
factor (BDNF), insulin-like growth factor (IGF-1), vascu-
lar endothelial growth factor (VEGF), neurotrophin-3
(NT3), fibroblast growth factor (FGF-2), glial cell line-
derived neurotrophic factor (GDNF), epidermal growth
factor (EGF) and nerve growth factor (NGF) appear to
increase in conjunction with exercise interventions, and
these trophic factors act as survival, proliferation and
maturation factors in specific cells in the brain
[98] . Upon
binding to their specific receptors, these factors can pro-
mote the activation of signaling pathways by activating
the Ras/Raf proteins, P13K (protein 13 kinase)/Akt (pro-
tein kinase B) and cAMP response element-binding
(CREB) protein, which is a protein that is associated with
transcription. The aforementioned neurotrophic factors
can even inhibit signals in the caspase-mediated apop-
totic pathway. In the CNS, these trophic factors can both
act as modulators and be modulated by neurotransmit-
ters, which may play a substantial role in determining an
individual’s level of cognition and behaviors. Sex hor-
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mones may be associated with the regulation and func-
tion of trophic factors
[99] .
In humans, atrial natriuretic peptide (ANP) has a
function in controlling the body’s water volume. ANP is
primarily involved in pathways that affect the hormones
of the renin-angiotensin system. Thus, ANP has been
shown to play an important role in regulating catechol-
amines and gonadal hormones in addition to modulating
the mood and behavioral functions that are mediated by
its association with vasopressin
[100] .
Chronic Exercise Mechanisms
The long-term effects of chronic participation in
physical exercise appear to result in different responses
and adaptations than those that can be observed follow-
ing acute exercise participation (after only one session).
Increases in CBF, the expression of a number of trophic
factors (BDNF, IGF-1, VEGF, NT3, FGF-2, GDNF, EGF
and NGF) and the induction of pro-inflammatory pro-
cesses promote neurogenesis, angiogenesis and synapto-
genesis
[98] . Moreover, other factors, such as increased
metabolism, cognitive stimulation, antidepressant use,
dietary restriction, social contact and environmental en-
richment, also promote cell proliferation
[101] . Howev-
er, aging, stress, neurodegenerative diseases and the ac-
cumulation of free radicals tend to inhibit neurogenesis
[98] . Interestingly, van Praag [102] postulated that ad-
hering to a diet that is rich in antioxidants and anti-in-
flammatory compounds in combination with voluntary
exercise participation would have significantly better re-
sults than either diet or exercise alone. Moreover, cogni-
tive stimulation, elevated VEGF levels, caloric restriction
and accelerated metabolism might contribute to en-
hanced angiogenesis
[102] . It is expected that the results
found in these animal studies will also be found in hu-
mans because the underlying mechanisms exhibit simi-
lar responses in animals and humans
[103] .
The activation of the hypothalamus-pituitary-adrenal
(HPA) axis, the stress axis, also changes in accordance
with the type, duration and intensity of physical exer-
cisethat an individual performs. When stimulated, the
hypothalamus releases corticotrophin-releasing hor-
mone (CRH). The release of CRH then stimulates the pi-
tuitary gland and results in the release of adrenocortico-
tropic hormone, which interacts with the adrenal gland
and causes it to secrete the stress hormone cortisol in hu-
mans or corticosterone in animals
[104] . Although phys-
ical exercise is an acute stressor, chronic exercise can have
neuroprotective effects instead. These effects are illustrat-
ed by the finding that subjects who had undergone phys-
ical training had lower levels of cortisol both at rest and
in response to a stressor than sedentary subjects
[105] .
Some of the hypotheses presented in the literature that
address the correlation between the HPA axis and exer-
cise suggest that biological changes in the activity of the
HPA axis, such as those associated with an enhanced den-
sity and efficiency of mineralocorticoid receptors, lower
cortisol levels and the inhibition of cortisol synthesis,
could be an efficient negative feedback mechanism
[104] .
In addition, an increased vasopressin/CRH ratio might
have positive effects on this negative feedback for chron-
ic stress through a reduction in pituitary stimulation
[106] . Moreover, the effect of decreased CRH mRNA
transcription in the paraventricular nucleus of the hypo-
thalamus could result in diminished activity in the ante-
rior pituitary. These changes may be associated with an
improved immune response
[107] .
Interestingly, in addition to human studies, animal
studies have shown that hormonal alterations can influ-
ence both behavior and alimentary functions by interact-
ing with anorexigenic factors, such as glucose and leptin,
and orexigenic factors, such as neuropeptide Y and ghre-
lin. These factors may regulate the food circuitry in the
ventrolateral hypothalamus. This system could be acti-
vated during stressful situations, and a combination of
amino acid intake and the activation of the HPA axis
could cause the body to store energy for use when coping
with a stressful situation
[108] .
Antioxidant effects have also been observed in indi-
viduals who have participated in aerobic exercise for an
extended period of time
[109] . These effects could be ex-
plained by ROS-mediated signaling; the mitochondrial
production of ROS that results from a high metabolicde-
mand may induce signaling mediated by nuclear factor-
κB. Nuclear factor-κB then induces the expression of
genes that encode antioxidant enzymes that combat the
accumulation of free radicals, such as superoxide dis-
mutase, catalase and glutathione peroxidase
[110] . Fur-
thermore, the increase in the concentration of ROS pri-
marily modulates the activity of intracellular pathways
that are involved in the behavior of exercise muscle fibers.
Consistent with this hypothesis, animal studies have
shown that an elevated concentration of ROS might acti-
vate the CREB protein and the peroxisome proliferator-
activated receptor-γ coactivator (PGC-1α) in the nucleus,
thereby inducing mitochondrial biogenesis. Thus, chron-
ic aerobic exercise may have both antioxidant-mediated
and mitochondrial biogenic activity
[110] .
Chronic exercise can even result in changes in genetic
structures, such as those of the telomeres in leukocytes.
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Individuals who practice moderate physical activity
appear to have longer telomeres than sedentary individuals
and those who practice exercise that is either higher or
lower in intensity. The reported results regarding wheth-
er physical exercise enhances telomerase activity are still
inconclusive
[111] .
Chronic Diseases
For individuals with depression, several biochemical,
physiological and neurophysiological analyses of exer-
cise-related effects on the brain have shown positive ef-
fects with regard to the alleviation of depressive symp-
toms. Moreover, the exercise-induced release of neu-
rotransmitters and the elevation in neurotrophin activity
contribute to both neuroplasticity
[5] and normal (un-
suppressed) cortical activity
[24] and may play a role in
explaining exercise-related reductions in the depressive
symptoms of MDD subjects and overall improvements
inmental health
[5] . Furthermore, evidence from an ani-
mal study showed that a combination of regular exercise
and pharmacological treatment contributed to a greater
observed increase in the expression of BDNF mRNA in
the dentate gyrus than either intervention alone
[112] .
The production of BDNF, IGF-1 and VEGF is impor-
tant not only for neurogenesis but also for the mainte-
nance of neurons
[113] and the prevention of PD. These
neurotrophic factors and others can be induced by mus-
cle contraction and can cross the blood-brain barrier.
Therefore, BDNF, IGF-1 and VEGF act directly on brain
structures. Moreover, ROS produced by exercise requires
greater antioxidant activity, which improves signaling re-
lated to deoxyribonucleic acid (DNA) repair and induces
Angiogenesis
Neurogenesis
ATP
Adenyl cyclase
Neurotransmitters
Neurobiology of exercise-the cell
Ion channels Trophic factors
ȜcAMP
After few
weeks
Trophic
factors
Endoplasmic reticulum
Protein synthesis
Endocannab.
Opioids
Monoamines
(NE, Dopa, 5HT)
Monoamines
(NE, Dopa, 5HT)
GABA
Glutamate
Ca
+
Ca
+
GPi GPe
Na
+
K
+
BDNF
IGF1
VEGF
GDNF
CREB
PKA
PKC
NO
Ras/Raf
MEK/ERK
Caspases
AMPK
BAD
Apoptosis
Antioxidants
mTor
S6K1/2
Mitochondrial
biogenesis
Mitochondria
PI3K/Akt
CaMKII
DNA
PGC1į
CREB
Fig. 3. Neurobiology of exercise = Endocannab = endocannabi-
noids; NE = norepinephrine; Dopa = dopamine; 5HT = serotonin;
Ca
+
= calcium ion; Na
+
= sodium ion; K
+
= potassium ion; GPi =
G protein inhibitors; GPe= G protein excitors; Adenyl Cyclase =
adenylate cyclase; CaMKII = calcium calmodulin-dependent pro-
tein kinase II; ATP = adenosine triphosphate; cAMP = cyclic ad-
enosine monophosphate; PKC = protein kinase C; PKA = protein
kinase A; NO = nitric oxide; PI3K = phosphoinositide 3-kinase;
mTOR = mammalian target of rapamycin; S6K1/2 = S6 kinase 1;
MEK = methyl ethyl ketone; ERK = extracellular signal-regulated
kinases; BAD = Bcl-2-associated death promoter; AMPK = AMP-
activated protein kinase.
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the production of antioxidant enzymes [114] . Altogether,
aerobic exercise induces PGC-1α, a factor that stimulates
mitochondrial biogenesis
[115] .
In conclusion, there are many neurobiological hy-
potheses that account for the variety of observed respons-
es to exercise. In general, physical exercise appears to
stimulate the synthesis and release of neuromodulators
that areimportant for the maintenance of behavior and
cognition beyond coping with stress, and exercise stimu-
lates the formation of new neurons and blood vessels,
thereby promoting mental health ( fig.3 ).
C o n c l u s i o n
We conclude that regular physical training can re-
duce the severity of several symptoms that are related to
various mental disorders such as depression, AD and
PD. There are many neurobiological hypotheses that
may explain the wide variety of observed responses to
exercise. Acute exercise appears to improve mood by ac-
tivating specific cortical areas and by inducing the re-
lease of neurotransmitters and trophic factors that con-
tribute to adherence to a program of regular physical
activity. Chronic physical exercise appears to induce
both neurogenesis and angiogenesis, which are impor-
tant for improving behavioral and cognitive function
and for improving the health of patients with mental dis-
orders. Moreover, as the studies of athletes that were dis-
cussed in this article have shown, physical exercise can
modulate mental health in both constructive and de-
structive ways.
A c k n o w l e d g m e n t
This research was supported in part by the Conselho Nacional
de Desenvolvimento Científico e Tecnológico (CNPq).
Disclosure Statement
The authors have no conflicts of interest to disclose.
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Chronic stress, even stress of a moderate intensity related to daily life, is widely acknowledged to be a predisposing or precipitating factor in neuropsychiatric diseases. There is a clear relationship between disturbances induced by stressful stimuli, especially long-lasting stimuli, and cognitive deficits in rodent models of affective disorders. Regular physical activity has a positive effect on the central nervous system (CNS) functions, contributes to an improvement in mood and of cognitive abilities (including memory and learning), and is correlated with an increase in the expression of the neurotrophic factors and markers of synaptic plasticity as well as a reduction in the inflammatory factors. Studies published so far show that the energy challenge caused by physical exercise can affect the CNS by improving cellular bioenergetics, stimulating the processes responsible for the removal of damaged organelles and molecules, and attenuating inflammation processes. Regular physical activity brings another important benefit: increased stress robustness. The evidence from animal studies is that a sedentary lifestyle is associated with stress vulnerability, whereas a physically active lifestyle is associated with stress resilience. Here, we have performed a comprehensive PubMed Search Strategy for accomplishing an exhaustive literature review. In this review, we discuss the findings from experimental studies on the molecular and neurobiological mechanisms underlying the impact of exercise on brain resilience. A thorough understanding of the mechanisms underlying the neuroprotective potential of preconditioning exercise and of the role of exercise in stress resilience, among other things, may open further options for prevention and therapy in the treatment of CNS diseases.
... Research on the protective effects of physical training and active lifestyles in the prevention of metabolic and cardiovascular disease is nothing new [13]. The effects of exercise on the brain, cognitive function and behaviour have also received considerable attention [14][15][16]. Since the classic study, in which it was first shown that animals subjected to voluntary exercise had increased neurogenesis [17], exercise has been seen as a potential enhancement of cognitive and behavioural functions in humans as well. ...
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... The positive association between CRF and AP explained by the risk of depression may be related to both psychological and physiological mechanisms. On the one hand, prior research in the adolescent population has shown that higher CRF is positively associated with better mood, self-esteem, and social support among equals, which may provide a sense of psychological well-being [31][32][33], diminishing depressive symptomatology. In fact, adolescents without depressive symptoms have a higher interest in school Table 3 Total, direct, and indirect effects, a Content courtesy of Springer Nature, terms of use apply. ...
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Chapter
The purpose of this chapter is to provide an overview of how physical exercise and sleep can affect brain function in ways that are important for everyone, but especially after surviving trauma. The role of physical exercise on cognitive function, aging, and mental health is addressed in addition to physical activity for children and implications for future research and public policy on physical exercise. Links are described between exercise, brain-derived neurotrophic factor (BDNF), irisin, epigenetics, and aging and brain health. Links are addressed between physical activity and sleep, in addition to the impact of sleep on the brain, ideal nightly sleep duration at different ages throughout the life course, sleep in youths, the significant impact of school start time, epigenetics, and links between religion, spirituality, forgiveness, and sleep are discussed here. Sleep hygiene pragmatics are also described in addition to directions for future research.KeywordsPhysical exercisePhysical activityPhysical exercise and cognitive functionPhysical exercise and mental healthPhysical activity for childrenIrisinEpigeneticsTelomerePhysical activity and sleepSleep and the brainIdeal nightly sleep durationSleep in youthsSchool start times and sleepReligionSpiritualityForgiveness and sleepSleep hygiene
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The affective changes associated with acute exercise have been studied extensively in exercise and health psychology, but not in affective psychology. This paper presents a summary of the relevant findings and a tentative theoretical model. According to this model, affective responses to exercise are jointly influenced by cognitive factors, such as physical self-efficacy, and interoceptive (e.g., muscular or respiratory) cues that reach the affective centres of the brain via subcortical routes. Furthermore, the balance between these two determinants is hypothesised to shift as a function of exercise intensity, with cognitive factors being dominant at low intensities and interoceptive cues gaining salience as intensity approaches the individual's functional limits and the maintenance of a physiological steady-state becomes impossible.
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01-02-02 The goal was to forecast the global burden of Alzheimer’s disease and evaluate the potential impact of interventions that delay disease onset or progression.
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