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

The Placebo Effect in Exercise and Mental Health Research

This chapter describes the placebo effect in the context of physical activity and mental health. Following a brief historical overview, definitions for placebos, placebo effects, and related terminology are discussed. Next, three major methodological challenges posed from studying the placebo effect in the context of exercise are described. Additionally, the role of a primary psychological mechanism of placebo and nocebo effects - expectations - will be summarized through the lens of key terminology. Findings from relevant chronic and acute exercise studies that have measured or manipulated exercise-associated expectations will be presented. The chapter concludes with recommendations for controlling or quantifying the placebo effect in exercise and mental health research and its implications in clinical practice.

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.

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.

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.

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.

Associations Between Occupational and Leisure-Time Physical Activity With Employee Stress, Burnout and Well-Being Among Healthcare Industry Workers

PURPOSE

Examine the associations of occupational and leisure-time physical activity with job stress, burnout, and well-being among healthcare industry workers.

DESIGN

Quantitative; cross-sectional.

SETTING

Healthcare Industry.

SAMPLE

US Amazon Mechanical Turk participants (n = 550) employed in the healthcare industry, worked 35 hours or more per week, had ≥ 1 supervisor and ≥ 1 co-worker, and were ≥ 18 years old.

MEASURES

Self-reported measures of occupational physical activity (OPA) and leisure-time physical activity (LTPA), employee well-being, job stress, and burnout operationalized as exhaustion and disengagement.

ANALYSIS

Associations between OPA and LTPA with employee well-being, job stress, exhaustion and disengagement were assessed with separate multiple linear regression models.

RESULTS

OPA had positive significant associations with job stress (β = 0.10, P value = .003) and exhaustion (β = 0.21, P value < .0001). No significant associations were found between OPA with other psychological outcomes. A significant inverse association was found between LTPA and exhaustion (β = -0.04, P value = .007).

CONCLUSION

In a sample of U.S. health care workers, and consistent with prior epidemiological studies, greater LTPA was associated with lower feelings of exhaustion. In contrast, health care workers with greater OPA reported higher perceptions of job stress and exhaustion. The findings underscore the need for more research aimed at understanding relationships between OPA and psychological health among healthcare workers.

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.