Advancing the understanding of placebo effects in psychological outcomes of exercise: Lessons learned and future directions

Associations between expected and observed psychological responses to acute resistance exercise in analogue generalized anxiety disorder

The role of expectations in psychological responses to acute resistance exercise (RE) is largely unknown. This study quantified associations between expectations regarding psychological responses to exercise and observed state anxiety and mood responses after acute RE among adults with and without Analogue Generalized Anxiety Disorder (AGAD). Acute RE was nested into week one of an eight-week RCT of RE among 56 young adults with AGAD (n = 25) and non-AGAD (n = 31). 23 young adults were randomized to the intervention group and 33 to seated quiet rest. State anxiety and mood were measured pre and 10 min-post acute RE or seated quiet rest (QR). Expectations were measured pre acute RE or QR. Spearman's rho quantified associations between expectations and mood responses. There were no associations in the acute RE sample between expectations of psychological outcomes and experienced psychological outcomes (all rho: -0.05 to 0.16) and the QR sample (all rho: -0.07 to 0.22). The measurement of Expected Psychological Outcomes of Exercise (EPOE) was not specific to RE modality alone, possibly influencing participants' responses. These preliminary findings suggest that post-acute RE mood responses are independent from expectations of psychological outcomes, which is paramount when promoting RE as a potential treatment/therapeutic option to improve mood. Future research should focus on expectations of psychological responses specifically to acute and chronic RE.

Impact of different exercise types on depression and anxiety in individuals with cancer: A systematic review and network meta-analysis of randomized controlled trials

OBJECTIVE

Various exercise modalities have been demonstrated to be effective in alleviating anxiety and depression among individuals with cancer. However, it remains unclear which specific exercise intervention is the optimal choice. This study aimed to systematically evaluate the impact of different exercise intervention types on anxiety and depression in individuals with cancer.

METHODS

Eligible randomized controlled trials were identified through searches of PubMed, Web of Science, and EBSCOHost, with the search period up to December 2024. Two researchers independently conducted the literature screening, data extraction, and assessment. Statistical analyses and visualizations were performed using Stata 15.0 software and RevMan5.4 software.

RESULTS

A total of 26 randomized controlled trials (involving 2118 individuals with cancer) examining three types of exercise interventions were included. Compared to usual care, mind-body exercise (SMD = -0.58, 95 % CI (-0.99, -0.17)), followed by resistance training (SMD = -0.52, 95 % CI (-1.12, 0.09)), and aerobic exercise (SMD = -0.51, 95 % CI (-0.89, -0.13)) significantly decreased depression levels among individuals with cancer. Additionally, resistance training (SMD = -0.66, 95 % CI (-1.59, 0.27)), followed by aerobic exercise (SMD = -0.59, 95 % CI (-1.08, -0.10)), and mind-body exercise (SMD = -0.48, 95 % CI (-0.96, 0.00)) significantly decreased anxiety levels among individuals with cancer compared to usual care.

CONCLUSION

The findings of this network meta-analysis suggest that mind-body exercise, resistance training, and aerobic exercise are all effective interventions for reducing anxiety and depression among individuals with cancer.

Acute ergogenic effects of repetitive maximal breath-holding maneuvers on hematological and physiological responses: a graded exercise test investigation

PURPOSE

Repetitive maximal breath-holds (BHs or apneas) have been noted to induce advantageous hematological and blood buffering changes. Building on this, the hypothesis was formulated that the execution of repeated maximal BH efforts might lead to subsequent enhancements in performance during a time-to-exhaustion test.

METHODS

This study investigated the acute effects of five static maximal breath-holding maneuvers conducted with face immersion in cold water (10 °C) on subsequent graded exercise test (GET) performance. Seventeen well-trained participants completed a GET on a motorized treadmill under two randomized cross-over conditions: baseline measurement (CON) and after five repeated maximal breath-holding efforts (EXP).

RESULTS

The GET protocol consists of incremental increases in speed until exhaustion. After the fifth breath-hold, participants in the EXP condition exhibited significant (P < 0.05) increases in hematocrit, hemoglobin concentration, red blood cell count, and muscle deoxygenation, accompanied by a reduction in blood lactate concentration (4.09 ± 2.21%, 3.9 ± 1.76%, 3.96 ± 2.1%, 81.48 ± 23.83%, and 15.22 ± 17.64%, respectively), compared to CON. During GET, the EXP condition showed a significantly (P < 0.05) delayed onset time of the second ventilatory threshold (3.14 ± 5.85%) and (P < 0.05) increased time to exhaustion (0.75 ± 1.02%).

CONCLUSION

This evidence suggests that repeated maximal static breath-holding maneuvers enhance the oxygen delivery system by increasing the circulation of reserve red blood cells, heightened muscle oxygen deoxygenation, enhanced aerobic metabolism utilization, and postponing the transition from aerobic to anaerobic metabolism, implying a potential ergogenic effect. While pre-exercise breath-holding shows promise for improving time-to-exhaustion and optimizing subsequent distance running performance, further in-depth investigation is essential to fully elucidate the underlying mechanistic factors.

The effects of acute exercise on emotional pattern separation in adolescents and young adults

Acute exercise has been associated with cognitive improvements, particularly in memory processes linked to the hippocampus, such as the ability to discriminate between similar stimuli, called hippocampal pattern separation. This can be assessed behaviorally with a mnemonic discrimination task and neurally with functional magnetic resonance imaging (fMRI). Additionally, previous research has shown an emotional modulatory effect on pattern separation, involving the amygdala. In this randomized between-subject study, we investigated whether a 10-minute bout of moderate-intensity exercise, compared to rest, could enhance pattern separation of neutral and emotional images in a group of healthy adolescents and young adults (n=53). Our results showed no significant effects of exercise on either mnemonic discrimination performance or neural activity in the hippocampus and amygdala. Additionally, arterial spin labeling (ASL) confirmed that there were no significant differences in cerebral blood flow between exercise and rest. We did observe worse discrimination for images with a higher similarity level and worse discrimination for highly similar positive images compared to negative and neutral images. However, there were no significant correlations between behavioral outcomes and neural activity. Exploratory analysis revealed a neural signal consistent with pattern completion in the bilateral CA1 and left CA3, but no evidence of pattern separation. Future studies should optimize the exercise characteristics necessary to robustly enhance pattern separation.

"I am open to self-belief": A study examining the impact of open-label effects on postexercise affect and postintervention exercise behaviour

The contribution of placebo effects can be measured by manipulating psychological factors, such as positive expectations for exercise outcomes, without the need for traditional placebos (such as inert substances). While placebo effects are well known, research has revealed intriguing findings suggesting that placebos can have beneficial effects even when studies are performed without deception. Open-label placebo (OLP) interventions (prescribed honestly), which harness the power of belief, may represent another effective method for enhancing the benefits of exercise effects. This study compared the efficacy of a conventional placebo intervention, an OLP intervention, and a control group among 89 individuals. Participants' levels of affective response after exercise and exercise behaviour were assessed during the intervention period (4 weeks) and at follow-up (4 weeks). The results revealed similar levels of improvement in all outcomes across the three conditions. Both the conventional placebo and OLP intervention groups exhibited greater enhancements in postexercise enjoyment. OLP interventions demonstrated distinct advantages in terms of remembered affect and expectation fulfilment. Nonetheless, neither intervention directly stimulated postintervention exercise behaviour. Future studies should continue to explore the impact of OLP interventions on adherence to exercise behaviour.

A study on acute expectation effects on affective state and intention after a brief full-body workout in a student sample

Brief exercise bouts can have positive effects on the affective state, which in turn could affect the intention for future exercise. Such benefits may be enhanced by manipulating expectations. The aim of this study was to examine whether the affective state after physical activity or the intention for future exercise can be influenced by manipulating expectations. Furthermore, the relationship between affect and intention was investigated. In an online experiment, 121 persons completed either a 10-minute workout (PA), a workout after manipulation of expectations (PA + EM), or a control intervention (CG) after randomized group allocation. Data on affective state, expectations, and intention were collected before and after the intervention using questionnaires. After intervention, PA groups showed significantly more positive values than CG in several affective parameters, in other affective parameters, only PA + EM differed from CG. Affect was positively associated with intention alongside outcome expectations. No difference was found in intention. Although no significant effects of expectation manipulation on affective state or intention were found, latent effects cannot be ruled out. Further exploration of the importance of word choice in describing physical activity in the context of interventions to increase physical activity is necessary. Here, affect should be considered.

Best practice exercise for emerging depression in multiple sclerosis: A systematic review and meta-analysis

OBJECTIVE

To examine the effects of instructor-led exercise on depression symptoms in adults with multiple sclerosis, with a focus on moderating factors to treatment response.

DATA SOURCES

Cochrane Library, Embase, PEDro, PsycINFO and PubMed databases were searched until 21 April 2024.

REVIEW METHODS

The reporting quality of included studies assessed (PEDro and TESTEX scales). Hedges' g effect sizes were calculated and pooled using random and mixed-effects modelling.

RESULTS

Twenty-two independent studies (k), representing 785 participants with relapsing remitting or progressive MS, were included. Individual studies varied in their reporting quality (PEDro range: 3-8) and did not routinely detail exercise parameters (TESTEX range: 5-13). Nonetheless, exercise reduced core symptoms of depression (gw = .52, CI: .30-.73, P < .01). Treatment effects were, however, not maintained once training had ceased (gw = -.53, CI: -.80 to .24, P ≤ .01, k = 5). Both aerobic and non-aerobic exercise groups experienced a significant (P < .01) reduction in depression scores. Larger gains were noted by those with better ambulation at baseline (P = .03).

CONCLUSION

Regular exercise can help to stabilise mood for people living with multiple sclerosis, regardless of session frequency or duration. Treatment efficacy could be maximised by addressing potential barriers for those with limited mobility, including exercise type, delivery and intensity. Protocol registered on Open Science Framework [https://osf.io/zfymq/].

Differential performance on a motor task according to the preference for task-irrelevant elements that are chosen or assigned: A randomized controlled study

This study explored the impact of choice and preference for what is chosen or assigned on performance on a motor task. Using an experimental design with a dart-throwing task, 90 novice participants were randomized into four groups: Choice-Like condition, Choice-Dislike condition, Assigned-Like condition, and Assigned-Dislike condition, resulting of the manipulation of choice (vs. assignation) of a task-irrelevant element and preference (irrelevant element: darts color and design). The study found that participants who were given the opportunity to choose their own dart for a throwing task performed better than those who were not given the choice. Participants who threw a dart they preferred also had better scores than those who threw a dart they did not like. However, the interactive effects of choice and preference on performance were inconclusive, and whereas being assigned with a disliked element was the worst condition for performance, and being allowed to choose preferred elements the most facilitatory one, nothing else can be concluded on the impact of both conditions alone or in combination. These results suggest that both choice and preference can positively impact performance in closed motor learning tasks and have practical applications for training and execution in athletic performance. Further investigations are warranted to delve into the interplay of choice and preference in diverse contexts and populations.

Chronic fatigue syndrome post-COVID-19: triple-blind randomised clinical trial of Astragalus root extract

OBJECTIVE

This study aimed to evaluate the effect of Astragalus root extract on nurses suffering from post-COVID-19 chronic fatigue syndrome.

MATERIALS AND METHODS

The study was designed as a triple-blind, randomised, controlled trial in Iran in 2023. 64 chronic fatigue syndrome nurses were randomly assigned to one of two groups: an intervention group (n=32) that received Astragalus root extract (500 mg two times per day) or a control group (n=32) that received a placebo. Changes in chronic fatigue syndrome scores were measured before to, at the end of and 1 month after the intervention. Data were analysed using descriptive and analytical statistics (T-tests, χ2, analysis of variances, Cochran's Q tests, McNemar and generalised estimating equations).

RESULTS

In comparison to before, chronic fatigue prevalence decreased statistically significantly at the end of the intervention group (13.8%) and 1 month later (17.2%). Further, the frequency differed between before and after (p=0.0001) and 1 month later (p=0.0001). In the control group, chronic fatigue was statistically significantly different before and after the intervention (72.2%; p=0.003). Having an underlying disease (B=0.84, OR=2.33; p=0.04) and being in the control group (B=2.15, OR=12.36; p=0.01) increased the risk of chronic fatigue, whereas increasing the length of time decreased it (B=-0.67, OR=0.50; p=0.0001).

CONCLUSION

Astragalus root extract has been shown to reduce chronic fatigue in nurses. Therefore, this herbal extract can be used to reduce the incidence and treatment of chronic fatigue in nurses.

Improving movement behavior in office workers: effects of two multi-level cluster-RCT interventions on mental health

BACKGROUND

We have previously reported on the design and efficacy of two cluster-randomized multi-level workplace interventions, attempting to decrease sedentary behavior (SED) or increase moderate to vigorous physical activity (MVPA) among office workers to improve mental health outcomes. The aim of this study was to investigate intervention effects on mental health outcomes, i.e., mental wellbeing, depression or anxiety symptoms, and stress immediately after the 6-month intervention period.

METHODS

Teams of 263 office workers were cluster-randomized to one of two interventions or a waitlist control group. The PA intervention (iPA) focused on increasing MVPA and the SED intervention (iSED) on reducing SED. Both multi-level interventions targeted individual office workers and their social, physical, and organizational work environment, incorporating counseling based on cognitive behavioral therapy and motivational interviewing. Mental health outcomes were assessed using validated questionnaires before and immediately after the intervention. Intervention effects were analyzed using linear mixed effects models.

RESULTS

Participants were mostly female and highly educated, with a mean age of 42 years and had favorable levels of mental health at baseline. Mental wellbeing improved for the iSED group (β = 8, 95% CI 1 to 15, p = 0.030) but not for the iPA group (β = 6, 95% CI -1 to 12, p = 0.072) compared to the control group. No effects were found for depression or anxiety symptoms or stress.

CONCLUSIONS

The multi-level interventions improved mental wellbeing among this population of office workers, reaching statistical significance in the iSED group. The size of the effect can be regarded meaningful, considering favorable mental health and high PA level at baseline. Thus, workplace interventions that provide support on multiple levels appear to have potential for improving mental wellbeing, but not reducing ill-health variables, among healthy office workers. More research is needed to understand the mechanisms through which such improvements can be achieved and to identify the most effective intervention components.

TRIAL REGISTRATION

ISRCTN92968402 (27 February 2018).

Exercise and Fear and Safety Learning

Fear conditioning paradigms have been studied for over 100 years and are of great interest to the behavioral and clinical sciences given that several safety learning processes (e.g., extinction learning and recall) are thought to be fundamental to the success of exposure-based therapies for anxiety and related disorders. This chapter provides an overview of preclinical and clinical investigations that examined the effects of exercise on initial fear acquisition, fear extinction learning and consolidation, and return of fear outcomes. This chapter highlights the collective body of evidence suggesting that exercise administered after extinction learning enhances the consolidation and subsequent recall of extinction memories to a greater extent than exercise administered prior to extinction learning. This suggests that the addition of exercise after exposure therapy sessions may improve treatment outcomes for people with anxiety and related disorders. Potential mechanisms are discussed in addition to suggestions for future research to improve our understanding of the effects of exercise on fear conditioning and extinction outcomes.

Exercise and Anxiety

Anxiety disorders are among the most commonly diagnosed mental health disorders in the United States - affecting over 40 million adults per year. Although anxiety disorders are commonly treated via psychotherapy and/or pharmacotherapy, there is also accumulating evidence to suggest that physical activity and exercise may play an important role in prevention and treatment. This chapter provides an extensive overview of literature examining the effects of physical activity, acute bouts of exercise, and chronic exercise training on several anxiety outcomes, primarily in adults. The collective evidence to date suggests that: (1) an acute bout of aerobic or resistance exercise generally results in reductions in state anxiety among adults with and without clinical anxiety disorders, (2) greater levels of physical activity are associated with fewer anxiety symptoms and a reduced likelihood of developing an anxiety disorder, (3) exercise training (aerobic and resistance) appears to reduce general anxiety symptoms in adults without a clinical anxiety disorder and adults with a chronic illness (e.g., cardiovascular disease) and may reduce disorder-specific symptoms of anxiety in adults with a clinical anxiety disorder. Although the collective body of evidence is promising, there is a need for additional well-designed and adequately powered randomized controlled trials, especially among adults with clinical anxiety disorders.

Endocannabinoid and psychological responses to acute resistance exercise in trained and untrained adults

INTRODUCTION

This study examined the effects of acute resistance exercise on circulating endocannabinoid (eCB) and mood responses in trained and untrained healthy adults.

METHODS

Thirty-two healthy adults (22.1 ± 2.9 years) were recruited from trained (reporting resistance exercise at least twice per week for ≥ previous three months) and untrained (performing no resistance exercise for ≥ previous three months) groups. Participants (13 male, 19 female) completed three sets of resistance exercise (16 repetitions at 50% 1-repetition max, 12 repetitions at 70% 1-repetition max, 8 repetitions at 80% 1-repetition max). Resistance machines targeted the legs, chest, back, and abdominal muscles. Mood states, affect, and circulating eCB concentrations were evaluated before and after resistance exercise.

RESULTS

There were significant decreases in AEA, PEA, and OEA levels following acute resistance exercise (p <0.05; ds = -0.39, -0.48, -0.65, respectively), with no significant group differences or group by time interactions. 2-AG did not change significantly. Positive affect increased significantly following resistance exercise (p = 0.009), while negative affect decreased (p <0.001). Depressive symptoms, anger, confusion, and total mood disturbance decreased significantly (p <0.05), while vigor increased significantly following resistance exercise (p = 0.005). There were no significant group differences or group by time interactions for any psychological outcomes.

CONCLUSION

These results indicate that acute resistance exercise may reduce eCB and related lipid concentrations, which is opposite to the increase in lipids typically observed with acute aerobic exercise. Furthermore, psychological improvements occur after resistance exercise regardless of decreases in eCBs, supporting the notion that psychological changes with exercise likely occur through a wide variety of biological and environmental mechanisms.

Expectations Come True: The Placebo Effect of Exercise on Affective Responses

Objective: This study investigated the placebo and nocebo effects of habitual and induced expectations. Methods: In Study 1, 95 participants (Mage = 19.65 ± 2.21 years, MBMI = 21.94 ± 2.55) were grouped according to habitual expectations (positive, neutral, or negative) and completed a 30-min moderate-intensity aerobic exercise, and their affective response, rating of perceived exertion (RPE), and heart rate variability (HRV) were measured before, during, and after the exercise. In Study 2, the participants from Study 1 were grouped according to induced expectations (control, positive, or negative) and completed a 30-min moderate-intensity aerobic exercise. Affective response, RPE, and HRV were measured before, during, and after exercise. Results: In Study 1, positive habitual expectations increased affective response during and after exercise [F(2, 92) = 2.959, p = .057, ηp2 = .060], and negative habitual expectations increased RPE during exercise [F(2, 92) = 5.174, p = .007, ηp2 = .101]. In Study 2, positive induced expectation increased affective response during [F(2, 86) = 5.492, p = .006, ηp2 = .113] and after exercise [F(2, 86) = 6.096, p = .003, ηp2 = .124] and was not affected by habitual expectation. Conclusion: The affective response during and after exercise is influenced by habitual and induced expectations. Positive expectations enhance affective benefits, while negative expectations reduce affective benefits.

Sodium Bicarbonate and Time-to-Exhaustion Cycling Performance: A Retrospective Analysis Exploring the Mediating Role of Expectation

BACKGROUND

Research has shown that ingesting 0.3 g·kg^-1 body mass sodium bicarbonate (NaHCO₃) can improve time-to-exhaustion (TTE) cycling performance, but the influence of psychophysiological mechanisms on ergogenic effects is not yet understood.

OBJECTIVE

This study retrospectively examined whether changes in TTE cycling performance are mediated by positive expectations of receiving NaHCO₃ and/or the decline in blood bicarbonate during exercise.

METHODS

In a randomised, crossover, counterbalanced, double-blind, placebo-controlled design, 12 recreationally trained cyclists (maximal oxygen consumption, 54.4 ± 5.7 mL·kg·min^-1) performed four TTE cycling tests 90 min after consuming: (1) 0.3 g·kg^-1 body mass NaHCO₃ in 5 mL·kg^-1 body mass solution, (2) 0.03 g·kg^-1 body mass sodium chloride in solution (placebo), (3) 0.3 g·kg^-1 body mass NaHCO₃ in capsules and (4) cornflour in capsules (placebo). Prior to exercise, participants rated on 1-5 Likert type scales how much they expected the treatment they believe had been given would improve performance. Capillary blood samples were measured for acid-base balance at baseline, pre-exercise and post-exercise.

RESULTS

Administering NaHCO₃ in solution and capsules improved TTE compared with their respective placebos (solution: 27.0 ± 21.9 s, p = 0.001; capsules: 23.0 ± 28.1 s, p = 0.016). Compared to capsules, NaHCO₃ administered via solution resulted in a higher expectancy about the benefits on TTE cycling performance (Median: 3.5 vs. 2.5, Z = 2.135, p = 0.033). Decline in blood bicarbonate during exercise was higher for NaHCO₃ given in solution compared to capsules (2.7 ± 2.1 mmol·L^-1, p = 0.001). Mediation analyses showed that improvements in TTE cycling were indirectly related to expectancy and decline in blood bicarbonate when NaHCO₃ was administered in solution but not capsules.

CONCLUSIONS

Participants' higher expectations when NaHCO₃ is administered in solution could result in them exerting themselves harder during TTE cycling, which subsequently leads to a greater decline in blood bicarbonate and larger improvements in performance.

KEY POINTS

Ingesting 0.3 g·kg^-1 body mass sodium bicarbonate in solution and capsules improved time-to-exhaustion cycling performance Positive expectancy about the benefits of sodium bicarbonate and decline in blood bicarbonate were higher when sodium bicarbonate was administered in solution compared with capsules Improvements in time-to-exhaustion cycling performance for sodium bicarbonate administered in solution were related to expectancy and the enhanced extracellular buffering response.

The Interplay Between Expected Psychological Responses to Exercise and Physical Activity in Analogue Generalized Anxiety Disorder: a Cross-sectional Study

BACKGROUND

Expectations for psychological responses to exercise are not well characterized, particularly in people at risk for anxiety-related illnesses. Given the substantial evidence for salutary effects of exercise on anxiety symptoms and emerging recognition for expectations as a critical mechanism of placebo/nocebo effects, this study explored the interplay between expectations and physical activity in young adults with and without analogue generalized anxiety disorder.

METHODS

Participants (N=470, 23.2±4.8 years, 63% female) completed a physical activity and mood survey, including a 7-day physical activity recall questionnaire, and a 20-item questionnaire designed to measure positive and negative expectations for psychological and perceptual responses to exercise, particularly expectations for symptoms in the generalized anxiety disorder symptom profile. Analogue generalized anxiety disorder status was determined using the Generalized Anxiety Disorder subscale of the Psychiatric Diagnostic Screening Questionnaire.

RESULTS

For select outcomes, expected exercise-induced changes significantly differed according to analogue generalized anxiety disorder (whole-body pain, sleep quality, psychological well-being, stress, relaxation) and active versus inactive (anxious mood, depressed mood, concentration, physical function, psychological well-being, relaxation) status. However, these findings did not survive corrections for multiple comparisons and the magnitude of these differences was small, approximating 0.25 standard deviations. Expectations for anxious (Spearman's ρ=-0.14, p≤0.002) and depressed mood (ρ=-0.15, p≤0.002), and psychological well-being (ρ=0.15, p≤0.001) were significantly associated with higher physical activity levels. Exercise expectations for anxious mood explained a significant, but small (+1.5%, p≤0.03), amount of variance in physical activity.

CONCLUSIONS

Expectations for exercise-induced improvements did not significantly differ between young adults based on analogue generalized anxiety disorder or physical activity status.

Aerobic exercise in the treatment of PTSD: An examination of preclinical and clinical laboratory findings, potential mechanisms, clinical implications, and future directions

Posttraumatic stress disorder (PTSD) is associated with heightened emotional responding, avoidance of trauma related stimuli, and physical health concerns (e.g., metabolic syndrome, type 2 diabetes, cardiovascular disease). Existing treatments such as exposure-based therapies (e.g., prolonged exposure) aim to reduce anxiety symptoms triggered by trauma reminders, and are hypothesized to work via mechanisms of extinction learning. However, these conventional gold standard psychotherapies do not address physical health concerns frequently presented in PTSD. In addition to widely documented physical and mental health benefits of exercise, emerging preclinical and clinical evidence supports the hypothesis that precisely timed administration of aerobic exercise can enhance the consolidation and subsequent recall of fear extinction learning. These findings suggest that aerobic exercise may be a promising adjunctive strategy for simultaneously improving physical health while enhancing the effects of exposure therapies, which is desirable given the suboptimal efficacy and remission rates. Accordingly, this review 1) encompasses an overview of preclinical and clinical exercise and fear conditioning studies which form the basis for this claim; 2) discusses several plausible mechanisms for enhanced consolidation of fear extinction memories following exercise, and 3) provides suggestions for future research that could advance the understanding of the potential importance of incorporating exercise into the treatment of PTSD.

Comparative Effectiveness of Multiple Exercise Interventions in the Treatment of Mental Health Disorders: A Systematic Review and Network Meta-Analysis

BACKGROUND

The efficacy of exercise interventions in the treatment of mental health disorders is well known, but research is lacking on the most efficient exercise type for specific mental health disorders.

OBJECTIVE

The present study aimed to compare and rank the effectiveness of various exercise types in the treatment of mental health disorders.

METHODS

The PubMed, Web of Science, PsycINFO, SPORTDiscus, CINAHL databases, and the Cochrane Central Register of Controlled Trials as well as Google Scholar were searched up to December 2021. We performed pairwise and network meta-analyses as well as meta-regression analyses for mental health disorders in general and each type of mental health disorder, with alterations in symptom severity as the primary outcome.

RESULTS

A total of 6456 participants from 117 randomized controlled trials were surveyed. The multimodal exercise (71%) had the highest probability of being the most efficient exercise for relieving depressive symptoms. While resistance exercise (60%) was more likely to be the most effective treatment for anxiety disorder, patients with post-traumatic stress disorder (PTSD) benefited more from mind-body exercise (52%). Furthermore, resistance exercise (31%) and multimodal exercise (37%) had more beneficial effects in the treatment of the positive and negative symptoms of schizophrenia, respectively. The length of intervention and exercise frequency independently moderated the effects of mind-body exercise on depressive (coefficient = 0.14, p = .03) and negative schizophrenia (coefficient = 0.96, p = .04) symptoms.

CONCLUSION

Multimodal exercise ranked best for treating depressive and negative schizophrenic symptoms, while resistance exercise seemed to be more beneficial for those with anxiety-related and positive schizophrenic symptoms. Mind-body exercise was recommended as the most promising exercise type in the treatment of PTSD. However, the findings should be treated with caution due to potential risk of bias in at least one dimension of assessment and low-to-moderate certainty of evidence. Trial Registration This systematic review was registered in the PROSPERO international prospective register of systematic reviews (CRD42022310237).

Influence of motivational placebo-related factors on the effects of exercise treatment in depressive adolescents

Recent meta-analyses reveal a moderate effect of physical activity (PA) in the treatment of adolescent depression. However, not only the underlying neurobiological mechanisms, also the influences of placebo-related motivational factors (beliefs and expectancies in sporting, enjoyment and prior sports experiences), are still unclear. Based on the data of our prior study "Mood Vibes", we hypothesized that placebo-inherent factors like positive prior sports experiences and motivational factors, (positive beliefs, expectancies, and enjoyment related to PA), would increase the effects of an add-on exercise-therapy in juvenile depression. From 64 included depressed adolescents, 41 underwent an intensive add-on PA-therapy. Motivational factors were assessed using sport-specific scales. The changes in depression scores under treatment were rated by self-rating scale (German "Childhood Depression Inventory", (DIKJ)). A mixed model for repeated measures (MMRM) was used to analyze the effects of the different motivational variates on DIKJ. While prior sports experiences had no impact, motivational factors showed a significant effect on PA-induced changes in DIKJ scores (p = 0.002). The demotivated participants improved less, whereas it was sufficient to be neutral towards sporting to benefit significantly more. Motivational placebo-related factors (beliefs, expectancies and enjoyment regarding PA) affected the outcomes of an exercise treatment in depressed adolescents. Yet, a neutral mindset was sufficient to profit more from PA. Prior sporting in the sense of positive conditioning and as a protective factor did not play a role. Knowledge about these influences could in a second step help to develop tailored therapies.

Chronic, acute and protocol-dependent effects of exercise on psycho-physiological health during long-term isolation and confinement

Exercise could prevent physical and psychological deteriorations, especially during pandemic times of lock-down scenarios and social isolation. But to meet both, the common exercise protocols require optimization based on holistic investigations and with respect to underlying processes. This study aimed to explore individual chronic and acute effects of continuous and interval running exercise on physical and cognitive performance, mood, and affect and underlying neurophysiological factors during a terrestrial simulated space mission. Six volunteers (three females) were isolated for 120 days. Accompanying exercise training consisted of a continuous and interval running protocol in a cross-over design. Incremental stage tests on a treadmill were done frequently to test physical performance. Actigraphy was used to monitor physical activity level. Cognitive performance, mood (MoodMeter®), affect (PANAS), brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1), vascular-endothelial growth factor (VEGF), and saliva cortisol were investigated prior to, four times during, and after isolation, pre- and post-exercise on two separate days, respectively. As a chronic effect, physical performance increased (and IGF-1 tended) in the course of isolation and training until the end of isolation. Subjective mood and affect state, as well as cognitive performance, basal BDNF and VEGF levels, were well-preserved across the intervention. No acute effects of exercise were detected, besides slower reaction time after exercise in two out of nine cognitive tests, testing sensorimotor speed and memory of complex figures. Consistently higher basal IGF-1 concentrations and faster reaction time in the psychomotor vigilance test were found for the continuous compared to the interval running protocol. The results suggest that 120 days of isolation and confinement can be undergone without cognitive and mental deteriorations. Regular, individual aerobic running training supporting physical fitness is hypothesized to play an important role in this regard. Continuous running exercise seems to trigger higher IGF-1 levels and vigilance compared to interval running. Systematic and prolonged investigations and larger sample size are required to follow up on exercise-protocol specific differences in order to optimize the exercise intervention for long-term psycho-physiological health and well-being.

Pain-Related Post-Exertional Malaise in Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS) and Fibromyalgia: A Systematic Review and Three-Level Meta-Analysis

OBJECTIVE

Myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) and fibromyalgia (FM) are two debilitating, moderately comorbid illnesses in which chronic musculoskeletal pain symptoms are prevalent. These individuals can experience post-exertional malaise (PEM), a phenomenon in which symptom severity is worsened for 24 hours or longer after physical stress, but the pain-related component of PEM is not well characterized.

DESIGN

Systematic review and meta-analysis.

METHODS

Case-control studies involving adults with ME/CFS or FM and measuring pain symptoms before and after exposure to a standardized aerobic exercise test were included. Hedges' d effect sizes were aggregated with random-effects models, and potential moderators were explored with meta-regression analysis. Results were adjusted for nesting effects with three-level modeling.

RESULTS

Forty-five effects were extracted from 15 studies involving 306 patients and 292 healthy controls. After adjusting for nesting effects, we observed a small to moderate effect indicating higher post-exercise pain in patients than in controls (Hedges' d = 0.42; 95% confidence interval [CI]: 0.16-0.67). The mean effect was significantly moderated by pain measurement time point (b = -0.19, z = -2.57, P = 0.01), such that studies measuring pain 8-72 hours after exercise showed larger effects (d = 0.71, 95% CI = 0.28-1.14) than did those measuring pain 0-2 hours after exercise (d = 0.32, 95% CI = 0.10-0.53).

CONCLUSIONS

People with ME/CFS and FM experience small to moderate increases in pain severity after exercise, which confirms pain as a component of PEM and emphasizes its debilitating impact in ME/CFS and FM. Future directions include determining mechanisms of pain-related PEM and developing exercise prescriptions that minimize symptom exacerbation in these illnesses.

Exoskeletons for workers: A case series study in an enclosures production line

This case-series study aims to investigate the effects of a passive shoulder support exoskeleton on experienced workers during their regular work shifts in an enclosures production site. Experimental activities included three sessions, two of which were conducted in-field (namely, at two workstations of the painting line, where panels were mounted and dismounted from the line; each session involved three participants), and one session was carried out in a realistic simulated environment (namely, the workstations were recreated in a laboratory; this session involved four participants). The effect of the exoskeleton was evaluated through electromyographic activity and perceived effort. After in-field sessions, device usability and user acceptance were also assessed. Data were reported individually for each participant. Results showed that the use of the exoskeleton reduced the total shoulder muscular activity compared to normal working conditions, in all subjects and experimental sessions. Similarly, the use of the exoskeleton resulted in reductions of the perceived effort in the shoulder, arm, and lower back. Overall, participants indicated high usability and acceptance of the device. This case series invites larger validation studies, also in diverse operational contexts.

Six weeks of resistance training (plus advice) vs advice only in hand osteoarthritis: A single-blind, randomised, controlled feasibility trial

BACKGROUND

People with hand osteoarthritis (OA) may benefit from resistance training interventions. To date the feasibility of a such interventions for symptomatic hand OA, as per international guidelines, is unknown.

OBJECTIVE

Determine the feasibility of a clinical trial comparing resistance training to an advice only control group in people with symptomatic hand OA.

DESIGN

Single-blind, randomised, controlled feasibility study.

METHODS

The American College of Rheumatology criteria for hand OA were utilised for inclusion. Participants were randomly allocated (1:1:1) to advice and blood flow restriction training (BFRT), advice and traditional high intensity training (HIT), or advice only (control). Participants receiving BFRT and HIT underwent supervised hand exercises three times a week for six weeks. Feasibility measures included recruitment rate, adherence, exercise induced pain, training acceptability, pain flares, and adverse events. Number of treatment responders, pain, grip strength, and hand function were also recorded.

RESULTS

In total, 191 participants were screened, 59 (31%) were included. Retention rate was 89% for BFRT and 79% for HIT. Exercise did not worsen pain following training sessions, and training acceptability was equal between groups. Pain flares occurred in 1.6% (BFRT) and 4% (HIT) out of all the training sessions. There was one adverse event in the HIT group, with the participants withdrawing from the study due to pain. The number of treatment responders, and improvements in pain, were greater with BFRT and HIT. Grip and function did not improve.

CONCLUSION

A clinical trial comparing resistance training to advice for people with symptomatic hand OA is feasible.

Can the add-on placebo effect augment the physical and mental health outcomes of exercise? A meta-analysis

This study aimed to clarify whether the add-on placebo effect can augment the psychological and physiological benefits of exercise. The inclusion criteria were met by 18 studies with 1,221 participants. The add-on placebo effects promoted a more positive affect (g = 0.430), greater self-esteem (g = 0.454), improved cardiorespiratory fitness (g = 0.273), and decreased perceived exertion (g = 0.476) and blood pressure (g = 0.268). Improved affect benefits were moderated by placebo type (elaboration > external medium), self-selected exercise intensity (no > yes), and exercise type (running > nonspecific). The results support the proposal that the add-on placebo effect can provide significant positive benefits for exercisers, particularly in terms of psychological responses.

Attempting to Separate Placebo Effects from Exercise in Chronic Pain: A Systematic Review and Meta-analysis

BACKGROUND

Pain is the most disabling characteristic of musculoskeletal disorders, and while exercise is promoted as an important treatment modality for chronic musculoskeletal conditions, the relative contribution of the specific effects of exercise training, placebo effects and non-specific effects such as natural history are not clear. The aim of this systematic review and meta-analysis was to determine the relative contribution of these factors to better understand the true effect of exercise training for reducing pain in chronic primary musculoskeletal pain conditions.

DESIGN

Systematic review with meta-analysis DATA SOURCES: MEDLINE, CINAHL, SPORTDiscus, EMBASE and CENTRAL from inception to February 2021. Reference lists of prior systematic reviews.

ELIGIBILITY CRITERIA

Randomised controlled trials of interventions that used exercise training compared to placebo, true control or usual care in adults with chronic primary musculoskeletal pain. The review was registered prospectively with PROSPERO (CRD42019141096).

RESULTS

We identified 79 eligible trials for quantitative analysis. Pairwise meta-analysis showed very low-quality evidence (GRADE criteria) that exercise training was not more effective than placebo (g [95% CI]: 0.94 [- 0.17, 2.06], P = 0.098, I² = 92.46%, studies: n = 4). Exercise training was more effective than true, no intervention controls (g [95% CI]: 0.99 [0.66, 1.32], P < 0.001, I² = 92.43%, studies: n = 42), usual care controls (g [95% CI]: 0.64 [0.44, 0.83], P < 0.001, I² = 76.52%, studies: n = 33), and when all controls combined (g [95% CI]: 0.84 [0.64, 1.04], P < 0.001, I² = 90.02%, studies: n = 79).

CONCLUSIONS

There is very low-quality evidence that exercise training is not more effective than non-exercise placebo treatments in chronic pain. Exercise training and the associated clinical encounter are more effective than true control or standard medical care for reductions in pain for adults with chronic musculoskeletal pain, with very low quality of evidence based on GRADE criteria.

A mixed-methods study to evaluate the effectiveness and cost-effectiveness of aerobic exercise for primary dysmenorrhea: A study protocol

BACKGROUND AND PURPOSE

Several studies have evaluated the effects of high-intensity aerobic training (HIAT) on pain severity and quality of life (QoL) among women with primary dysmenorrhea. However, to date, no studies have evaluated the effectiveness of HIAT on academic performance or absenteeism or examined the cost-effectiveness of HIAT relative to other treatments in women with primary dysmenorrhea. Furthermore, the mechanisms underlying aerobic exercise-induced analgesia in primary dysmenorrhea remain unclear. The objectives of this study are to: (1) evaluate the effects of HIAT on absenteeism and academic performance among university students, (2) identify the underlying mechanisms associated with aerobic exercise-induced analgesia in primary dysmenorrhea, and (3) determine the cost-effectiveness of HIAT compared with a wait-list control (WLC) group receiving usual care.

METHODS

A sequential, embedded, mixed-methods study design, including a crossover, randomised controlled trial (RCT) and semi-structured focus groups, will be conducted alongside an economic evaluation. A total of 130 women aged 18-24 years will be randomised into either HIAT (n = 65) or wait-list control (n = 65) groups. Primary outcomes will include average pain intensity, absenteeism from university, and academic performance. Primary mediators will include salivary progesterone and prostaglandin F2α levels. Outcome and meditator variables will be assessed at baseline and post-treatment, at 12 and 28 weeks. An economic analysis will be conducted from the societal and healthcare perspective of Hong Kong. Semi-structured focus groups will be conducted at 32 weeks. Of the 130 participants included in the RCT, 70 will be included in the focus groups.

STATISTICAL ANALYSIS

All statistical analyses will be performed on an intention-to-treat basis, using SPSS (version 24). Preliminary analysis using an independent samples t-test and a two-sided, unpaired Student's t-test will be performed to exclude carryover effects and identify within-participant differences in outcome variables between the study periods, respectively. Treatment effects will be evaluated using analysis of variance via a mixed-effects model with fixed effects for intervention, period, and sequence. In all models, random effects will include the participants nested within the sequence as a sampling cluster. The mediation effects will be assessed using the Sobel test. The EQ-5D responses will be converted into utility scores to estimate the gain or loss of quality-adjusted life-years. Seemingly unrelated regression analyses will be used to estimate the total cost differences and effect differences. Qualitative data will be analysed using the process of thematic analysis.

Causes and Consequences of Interindividual Response Variability: A Call to Apply a More Rigorous Research Design in Acute Exercise-Cognition Studies

The different responses of humans to an apparently equivalent stimulus are called interindividual response variability. This phenomenon has gained more and more attention in research in recent years. The research field of exercise-cognition has also taken up this topic, as shown by a growing number of studies published in the past decade. In this perspective article, we aim to prompt the progress of this research field by (i) discussing the causes and consequences of interindividual variability, (ii) critically examining published studies that have investigated interindividual variability of neurocognitive outcome parameters in response to acute physical exercises, and (iii) providing recommendations for future studies, based on our critical examination. The provided recommendations, which advocate for a more rigorous study design, are intended to help researchers in the field to design studies allowing them to draw robust conclusions. This, in turn, is very likely to foster the development of this research field and the practical application of the findings.

Five repeated maximal efforts of apneas increase the time to exhaustion in subsequent high-intensity exercise

Ten subjects were tested on a cycle ergometer to exhaustion with intensity corresponding to 150 % of their peak power output (TF150) under three conditions [C: base line measurement; PRE: after five repeated breath hold maneuvers (BH); and POST: after 5BH, preceded by two weeks of BH training]. Respiratory and blood measurements were carried out. Upon cessation of 5BH, subjects compared to C condition started TF150 with reduced arterialized blood pH (C:7.428±0.023, PRE:7.419±0.016, POST:7.398±0.021) and elevated bicarbonate concentration (mmol/l), ventilation (l/min) and oxygen uptake (ml/min) (C:28.4±1.5, PRE:29.9±1.2, POST:30.0±1.8; C:10.4±2.5, PRE:13.3±3.3, POST:15.6±5.6; C:333.0±113.8, PRE:550.1±131.1, POST:585.1±192.8, respectively). After TF150, subjects had significantly reduced pH and elevated ventilation, and oxygen uptake in PRE and POST, in comparison to the C condition. TF150 (sec) significantly improved after 5BH without being further affected by BH training (C:44.8±8.1, PRE:49.2±4.8, POST:49.3±8.2). Priming breath holds prior to middle-distance racing may improve performance.

Brain Structure, Cardiorespiratory Fitness, and Executive Control Changes after a 9-Week Exercise Intervention in Young Adults: A Randomized Controlled Trial

Cardiorespiratory fitness (CRF) is assumed to exert beneficial effects on brain structure and executive control (EC) performance. However, empirical evidence of exercise-induced cognitive enhancement is not conclusive, and the role of CRF in younger adults is not fully understood. Here, we conducted a study in which healthy young adults took part in a moderate aerobic exercise intervention program for 9 weeks (exercise group; n = 48), or control condition of non-aerobic exercise intervention (waitlist control group; n = 72). Before and after the intervention period maximal oxygen uptake (VO2max) as an indicator of CRF, the Flanker task as a measure of EC performance and grey matter volume (GMV), as well as cortical thickness via structural magnetic resonance imaging (MRI), were assessed. Compared to the control group, the CRF (heart rate, p < 0.001; VO2max, p < 0.001) and EC performance (congruent and incongruent reaction time, p = 0.011, p < 0.001) of the exercise group were significantly improved after the 9-week aerobic exercise intervention. Furthermore, GMV changes in the left medial frontal gyrus increased in the exercise group, whereas they were significantly reduced in the control group. Likewise, analysis of cortical morphology revealed that the left lateral occipital cortex (LOC.L) and the left precuneus (PCUN.L) thickness were considerably increased in the exercise group, which was not observed in the control group. The exploration analysis confirmed that CRF improvements are linked to EC improvement and frontal grey matter changes. In summary, our results support the idea that regular endurance exercises are an important determinant for brain health and cognitive performance even in a cohort of younger adults.

Perceived exertion and performance modulation: effects of caffeine ingestion and subject expectation

BACKGROUND

It is well established that caffeine has ergogenic effects on endurance performance. This evidence often comes from studies in which subjects receive either caffeine or placebo in double-blind, randomized and counterbalanced order. Here, we propose a new methodology which aims to estimate the effects of participant expectancy of ergogenic or anti-ergogenic effects on performance.

METHODS

Sixteen physically active participants (non-athletes engaged in systematic physical training >3 months, at least three times a week) performed three 30-minute running tests after being told they would be provided with either a harmful treatment (lactic acid), a beneficial treatment (caffeine) or a placebo. In each blinded case, subjects were given caffeine. The velocity and Rating of Perceived Exertion (RPE) during the time trial were examined in light of the participant's expectancy before and after the endurance event using Bayesian multilevel models.

RESULTS

For pre-exercise expectancy, there is a 92% probability that caffeine expectation decreases RPE (posterior median±SD -0.65±0.36) and a 79% probability that lactic acid expectation increases RPE (posterior median±SD 0.58±0.47) with expectations for placebo and 'not sure' falling in between (posterior median±SD: -0.37±0.32 and -0.22±0.37, respectively). In general, our interventions suggest an 81% probability that caffeine lowers RPE. However, there was no effect of caffeine supplementation on running velocity (median±SD 0.04±0.08 km.h^-1).

CONCLUSIONS

When a participant believed they are under a potentially positive treatment, their RPE decreased but if they believed themselves to be under a harmful treatment, their RPE increased, regardless of the actual positive intervention; neither caffeine nor the expectancy of a particular intervention improved actual performance as measured by running velocity in a 30-minute period.

Resistance exercise training for anxiety and worry symptoms among young adults: a randomized controlled trial

This trial quantified the effects of ecologically-valid resistance exercise training (RET) on anxiety and worry symptoms among young adults. Young adults not meeting criteria for subclinical, or analogue Generalized Anxiety Disorder (AGAD) were randomized to an eight-week RET intervention, or eight-week wait-list. AGAD status was determined using validated cut-scores for both the Psychiatric Diagnostic Screening Questionnaire-Generalized Anxiety Disorder subscale (≥ 6) and Penn State Worry Questionnaire (≥ 45). The primary outcome was anxiety symptoms measured with the Trait Anxiety subscale of the State-Trait Anxiety Inventory. The RET was designed according to World Health Organization and American College of Sports Medicine guidelines. RM-ANCOVA examined differences between RET and wait-list over time. Significant interactions were decomposed with simple effects analysis. Hedges' d effect sizes quantified magnitude of differences in change between RET and wait-list. Twenty-eight participants (64% female) fully engaged in the trial (mean age: 26.0 ± 6.2y, RET: n = 14; Wait-list: n = 14). A significant group X time interaction was found for anxiety symptoms (F_(3,66) = 3.60, p ≤ 0.019; d = 0.85, 95%CI: 0.06 to 1.63). RET significantly reduced anxiety symptoms from baseline to post-intervention (mean difference =  - 7.89, p ≤ 0.001). No significant interaction was found for worry (F_(3,69) = 0.79, p ≥ 0.50; d =  - 0.22, 95%CI: - 0.96 to 0.53). Ecologically-valid RET significantly improves anxiety symptoms among young adults.Trial Registration: Clinicaltrials.gov Identifier: NCT04116944, 07/10/2019.

Intrinsic Connectivity Changes Mediate the Beneficial Effect of Cardiovascular Exercise on Sustained Visual Attention

Cardiovascular exercise (CE) is an evidence-based healthy lifestyle strategy. Yet, little is known about its effects on brain and cognition in young adults. Furthermore, evidence supporting a causal path linking CE to human cognitive performance via neuroplasticity is currently lacking. To understand the brain networks that mediate the CE-cognition relationship, we conducted a longitudinal, controlled trial with healthy human participants to compare the effects of a 2-week CE intervention against a non-CE control group on cognitive performance. Concomitantly, we used structural and functional magnetic resonance imaging to investigate the neural mechanisms mediating between CE and cognition. On the behavioral level, we found that CE improved sustained attention, but not processing speed or short-term memory. Using graph theoretical measures and statistical mediation analysis, we found that a localized increase in eigenvector centrality in the left middle frontal gyrus, probably reflecting changes within an attention-related network, conveyed the effect of CE on cognition. Finally, we found CE-induced changes in white matter microstructure that correlated with intrinsic connectivity changes (intermodal correlation). These results suggest that CE is a promising intervention strategy to improve sustained attention via brain plasticity in young, healthy adults.

Influence of Music on Closed Motor Skills: A Controlled Study with Novice Female Dart-Throwers

The influence of music heard at different tempos is analyzed during the execution of a dart-throwing task. The sample consisted of 56 female university students (Mean age = 23.38, SD = 6.773). The participants were randomly assigned to GC (group control without music; n = 18), GS (group with slow-paced music at a tempo of 60 BPM; n = 19) and GF (group with fast-paced music at a tempo of 105 BPM; n = 19). All participants performed a dart-throwing task in two phases. Analysis of the scores obtained during Phase 1 and Phase 2 of dart throwing (examining both between-group differences and within-group differences, i.e., changes in scores from Phase 1 to Phase 2 using a mixed factorial ANOVA) revealed no differences in dart-throwing scores. There were, however, differences in execution time, where the participants in GS needed more time to complete the task than those in GF (F_(2,55) = 4.426, p = 0.017) with a large effect size (ŋ²_p = 0.143), although neither of these groups differed from GC. The results are discussed in terms of the role of music in precision tasks and the synchronization of the task with the pace of the music.

Incorporating methods and findings from neuroscience to better understand placebo and nocebo effects in sport

Placebo and nocebo effects are a factor in sports performance. However, the majority of published studies in sport science are descriptive and speculative regarding mechanisms. It is therefore not unreasonable for the sceptic to argue that placebo and nocebo effects in sport are illusory, and might be better explained by variations in phenomena such as motivation. It is likely that, in sport at least, placebo and nocebo effects will remain in this empirical grey area until researchers provide stronger mechanistic evidence. Recent research in neuroscience has identified a number of consistent, discrete and interacting neurobiological and physiological pathways associated with placebo and nocebo effects, with many studies reporting data of potential interest to sport scientists, for example relating to pain, fatigue and motor control. Findings suggest that placebos and nocebos result in activity of the opioid, endocannabinoid and dopamine neurotransmitter systems, brain regions including the motor cortex and striatum, and measureable effects on the autonomic nervous system. Many studies have demonstrated that placebo and nocebo effects associated with a treatment, for example an inert treatment presented as an analgesic or stimulant, exhibit mechanisms similar or identical to the verum or true treatment. Such findings suggest the possibility of a wide range of distinct placebo and nocebo mechanisms that might influence sports performance. In the present paper, we present some of the findings from neuroscience. Focussing on fatigue as an outcome and caffeine as vehicle, we propose three approaches that researchers in sport might incorporate in their studies in order to better elucidate mechanisms of placebo/nocebo effects on performance.

The Contribution of Functional Magnetic Resonance Imaging to the Understanding of the Effects of Acute Physical Exercise on Cognition

The fact that a single bout of acute physical exercise has a positive impact on cognition is well-established in the literature, but the neural correlates that underlie these cognitive improvements are not well understood. Here, the use of neuroimaging techniques, such as functional magnetic resonance imaging (fMRI), offers great potential, which is just starting to be recognized. This review aims at providing an overview of those studies that used fMRI to investigate the effects of acute physical exercises on cerebral hemodynamics and cognition. To this end, a systematic literature survey was conducted by two independent reviewers across five electronic databases. The search returned 668 studies, of which 14 studies met the inclusion criteria and were analyzed in this systematic review. Although the findings of the reviewed studies suggest that acute physical exercise (e.g., cycling) leads to profound changes in functional brain activation, the small number of available studies and the great variability in the study protocols limits the conclusions that can be drawn with certainty. In order to overcome these limitations, new, more well-designed trials are needed that (i) use a more rigorous study design, (ii) apply more sophisticated filter methods in fMRI data analysis, (iii) describe the applied processing steps of fMRI data analysis in more detail, and (iv) provide a more precise exercise prescription.

Understanding placebo and nocebo effects in the context of sport: A psychological perspective

Research over the past 15 years on the placebo effect has substantiated its contribution to the efficacy of established treatments for a range of clinical conditions and identified its underlying mechanisms. There is also evidence that placebo effects contribute to the performance benefits of many ergogenic aids, and that performance can worsen when dummy treatments are associated with expectations of a harmful outcome (i.e. nocebo effect). Unfortunately, the bulk of sport research involving placebos and nocebos continues to be hampered by outdated definitions and conceptualizations of placebo effects and their mechanisms. This has implications not only for research but also application, as nearly 50% of athletes report experiencing a beneficial placebo effect, and a similar proportion of coaches report providing placebos to their athletes. The objective of this paper is to attempt to stimulate research by presenting updated definitions of placebo and nocebo effects in the context of sport, describing their major mechanisms and, highlighting the importance of the psychosocial context on placebo effects in the sport setting.

Dose-Response Matters! - A Perspective on the Exercise Prescription in Exercise-Cognition Research

In general, it is well recognized that both acute physical exercises and regular physical training influence brain plasticity and cognitive functions positively. However, growing evidence shows that the same physical exercises induce very heterogeneous outcomes across individuals. In an attempt to better understand this interindividual heterogeneity in response to acute and regular physical exercising, most research, so far, has focused on non-modifiable factors such as sex and different genotypes, while relatively little attention has been paid to exercise prescription as a modifiable factor. With an adapted exercise prescription, dosage can be made comparable across individuals, a procedure that is necessary to better understand the dose-response relationship in exercise-cognition research. This improved understanding of dose-response relationships could help to design more efficient physical training approaches against, for instance, cognitive decline.

Reconceptualizing the measurement of expectations to better understand placebo and nocebo effects in psychological responses to exercise

The understanding of placebo and nocebo effects in psychological responses to exercise may be improved by measuring expectations. Despite availability of several validated expectation measures, we argue for using scales that take both positive and negative expectations for exercise-induced changes into account. A cross-sectional survey was used to collect information on positive and negative expectations pertaining to how exercise would affect 14 different outcomes related to psychological health (n = 966). Outcomes for which a majority of the sample (>50%) reported positive expectations for exercise-induced changes included: psychological well-being (75.3%), depression (74.3%), relaxation (74.2%), sleep quality (73.3%), stress (72.2%), anxiety (69.8%), energy (67.1%), and attention (60.2%). Outcomes for which a majority of the sample (>50%) reported a negative expectation for exercise-induced changes were muscle pain (66.3%), fatigue (57.3%), and joint pain (50.7%). Across all 14 outcomes, the percentage of participants with negative expectations for exercise-induced changes ranged from 5.9 to 66.3%. Elucidating the potential presence of placebo and nocebo effects through measurement of expectations may improve the understanding of variability in the direction and magnitude of exercise-related effects on psychological health. Although there were only 3 outcomes for which the majority of participants reported negative expectations, we found that negative expectations were present to some degree for all 14 outcomes. Thus, for researchers who wish to characterize expectations in studies of psychological responses to exercise, we recommend using measures that give equal consideration to positive and negative expectations.