Psychological stress during exercise: cardiorespiratory and hormonal responses

A Ketone Monoester with Carbohydrate Improves Cognitive Measures Postexercise, but Not Performance in Trained Females

PURPOSE

The acute ingestion of a ketone monoester with the coingestion of a carbohydrate (KME + CHO) compared with carbohydrate (CHO) was investigated on cycling performance and cognitive performance in trained females.

METHODS

Using a two condition, placebo-controlled, double-blinded and crossover design, 12 trained females (mean ± SD: age, 23 ± 3 yr; height, 1.64 ± 0.08 m; mass, 65.2 ± 12.7 kg) completed a baseline assessment of cognitive performance (psychomotor vigilance testing (PVT), task switching, and incongruent flanker), followed by 6 × 5-min intervals at 40%, 45%, 50%, 55%, 60%, and 65% of their maximal power output (W max ) and then a 10-km time trial, concluding with the same assessments of cognitive performance. Participants consumed either 375 mg·kg -1 body mass of KME with a 6% CHO solution (1 g·min -1 of exercise) or CHO alone, across three boluses (50:25:25).

RESULTS

Blood β-hydroxybutyrate concentrations averaged 1.80 ± 0.07 and 0.13 ± 0.01 mM during exercise in KME + CHO and CHO, respectively. Blood glucose decreased after drink 1 of KME + CHO (~15%; P = 0.01) but not CHO, and lactate concentrations were lower in KME + CHO at 50%, 55%, 60%, and 65% W max (all P < 0.05) compared with CHO. Despite these changes, no differences were found between conditions for time trial finishing times (KME + CHO, 29.7 ± 5.7 min; CHO, 29.6 ± 5.7 min; P = 0.92). However, only KME + CHO resulted in increases in psychomotor vigilance testing speed (~4%; P = 0.01) and faster reaction times (~14%; P < 0.01), speed (~15%; P < 0.01), and correct responses (~13%; P = 0.03) in the incongruent flanker during posttesting compared with CHO.

CONCLUSIONS

The acute ingestion of a KME + CHO elevated blood β-hydroxybutyrate and lowered glucose and lactate across multiple time points during exercise compared with CHO. Although these changes did not affect physical performance, several markers of cognitive performance were improved by the addition of a KME in trained females.

The Acute and Chronic Effects of Lion's Mane Mushroom Supplementation on Cognitive Function, Stress and Mood in Young Adults: A Double-Blind, Parallel Groups, Pilot Study

BACKGROUND

Given the bioactive properties and limited work to date, Hericium erinaceus (Lion's mane) shows promise in improving cognitive function and mood. However, much of the human research has concentrated on chronic supplementation in cognitively compromised cohorts.

OBJECTIVE

The current pilot study investigated the acute and chronic (28-day) cognitive and mood-enhancing effects of Hericium erinaceus in a healthy, young adult cohort.

DESIGN

This randomized, double-blind, placebo-controlled, parallel-groups design investigated the acute (60 min post dose) and chronic (28-day intervention) effects of 1.8 g Hericium erinaceus in 41 healthy adults aged 18-45 years.

RESULTS

Analysis revealed that following a single dose of Hericium erinaceus, participants performed quicker on the Stroop task (p = 0.005) at 60 min post dose. A trend towards reduced subjective stress was observed following 28-day supplementation (p = 0.051).

CONCLUSIONS

The findings tentatively suggest that Hericium erinaceus may improve speed of performance and reduce subjective stress in healthy, young adults. However, null and limited negative findings were also observed. Given the small sample size, these findings should be interpreted with caution. Further investigation in larger sample sizes is crucial, however the findings of this trial offer a promising avenue of interest.

Hot spring bathing is associated with a lower prevalence of hypertension among Japanese older adults: a cross-sectional study in Beppu

Hot spring bathing is practiced to help manage various diseases, including hypertension. We investigated the preventive effects on hypertension of hot spring bathing among older adults in a data analysis using responses to a previous questionnaire with the aim to identify a novel approach in the prevention and management of hypertension. Among 10,428 adults aged ≥ 65 years, we assessed the hot spring bathing habits of 4001 individuals with a history of hypertension. We calculated odds ratios (OR) with 95% confidence intervals using a multivariable logistic regression model for history of hypertension. In multivariable logistic regression, age (≥ 85 years: OR, 1.410); history of arrythmia (OR, 1.580), stroke (OR, 1.590), gout (OR, 1.880), diabetes mellitus (OR, 1.470), hyperlipidemia (OR, 1.680), renal disease (OR, 1.520), chronic hepatitis (OR, 0.648); and hot spring bathing at 19:00 or later (OR, 0.850) were independently and significantly associated with hypertension during the lifetime. We found an inverse relationship between habitual nighttime hot spring bathing and a history of depression. Prospective randomized controlled trials on nighttime hot spring bathing as a treatment for hypertension are warranted to investigate whether nighttime hot spring bathing can help in preventing hypertension among adults aged ≥ 65 years.

International society of sports nutrition position stand: tactical athlete nutrition

This position stand aims to provide an evidence-based summary of the energy and nutritional demands of tactical athletes to promote optimal health and performance while keeping in mind the unique challenges faced due to work schedules, job demands, and austere environments. After a critical analysis of the literature, the following nutritional guidelines represent the position of the International Society of Sports Nutrition (ISSN).

General Recommendations

Nutritional considerations should include the provision and timing of adequate calories, macronutrients, and fluid to meet daily needs as well as strategic nutritional supplementation to improve physical, cognitive, and occupational performance outcomes; reduce risk of injury, obesity, and cardiometabolic disease; reduce the potential for a fatal mistake; and promote occupational readiness.

Military Recommendations

Energy demands should be met by utilizing the Military Dietary Reference Intakes (MDRIs) established and codified in Army Regulation 40-25. Although research is somewhat limited, military personnel may also benefit from caffeine, creatine monohydrate, essential amino acids, protein, omega-3-fatty acids, beta-alanine, and L-tyrosine supplementation, especially during high-stress conditions.

First Responder Recommendations

Specific energy needs are unknown and may vary depending on occupation-specific tasks. It is likely the general caloric intake and macronutrient guidelines for recreational athletes or the Acceptable Macronutrient Distribution Ranges for the general healthy adult population may benefit first responders. Strategies such as implementing wellness policies, setting up supportive food environments, encouraging healthier food systems, and using community resources to offer evidence-based nutrition classes are inexpensive and potentially meaningful ways to improve physical activity and diet habits. The following provides a more detailed overview of the literature and recommendations for these populations.

An Exploratory Study on the Physical Activity Health Paradox-Musculoskeletal Pain and Cardiovascular Load during Work and Leisure in Construction and Healthcare Workers

Using a novel approach, this exploratory study investigated whether the physical activity (PA) paradox extends to cardiovascular load and musculoskeletal pain. At baseline, 1–2 days of 24 h heart rate was assessed in 72 workers from construction and healthcare. Workers then reported pain intensity in 9 body regions (scale 0–3) every 6 months for two years. The 2 year average of musculoskeletal pain (sum of 9 pain scores; scale 0–27) was regressed on time spent during work and leisure above three thresholds of percentage heart rate reserve (%HRR), i.e., ≥20 %HRR, ≥30 %HRR, and ≥40 %HRR, using a novel ilr structure in compositional data analysis. Analyses were stratified for several important variables. Workers spending more time in physical activity at work had higher pain, while workers with more time in physical activity during leisure had less pain (i.e., the PA paradox), but none of the associations were statistically significant. Higher aerobic capacity and lower body mass index lowered the pain score among those with higher physical activity at work. This exploratory study suggests that the PA paradox may apply to musculoskeletal pain and future studies with larger sample sizes and additional exposure analyses are needed to explain why this occurs.

The Cardiometabolic Health Benefits of Sauna Exposure in Individuals with High-Stress Occupations. A Mechanistic Review

Components of the metabolic syndrome (i.e., hypertension, insulin resistance, obesity, atherosclerosis) are a leading cause of death in the United States and result in low-grade chronic inflammation, excessive oxidative stress, and the eventual development of cardiometabolic diseases (CMD). High-stress occupations (HSO: firefighters, police, military personnel, first responders, etc.) increase the risk of developing CMD because they expose individuals to chronic and multiple stressors (i.e., sleep deprivation, poor nutrition habits, lack of physical activity, psychological stress). Interestingly, heat exposure and, more specifically, sauna bathing have been shown to improve multiple markers of CMD, potentially acting as hormetic stressors, at the cellular level and in the whole organism. Therefore, sauna bathing might be a practical and alternative intervention for disease prevention for individuals with HSO. The purpose of this review is to detail the mechanisms and pathways involved in the response to both acute and chronic sauna bathing and collectively present sauna bathing as a potential treatment, in addition to current standard of care, for mitigating CMD to both clinicians and individuals serving in HSO.

Exogenous Ketones as Therapeutic Signaling Molecules in High-Stress Occupations: Implications for Mitigating Oxidative Stress and Mitochondrial Dysfunction in Future Research

High-stress occupations (ie, firefighters, military personnel, police officers, etc.) are often plagued by cardiometabolic diseases induced by exposure to chronic stressors. Interrupted sleep cycles, poor dietary patterns, lack of physical activity, and smoke exposure along with simultaneous psychological stressors promote chronic low-grade inflammation and excessive oxidative stress. Collectively, these data suggest that practical interventions which might mitigate the underlying pathologies of these cardiometabolic diseases are warranted. Ketones, specifically R-βHB, modulates intracellular signaling cascades such as the cellular redox ratios of NAD+/NADH, the activity of NAD dependent deacetylases SIRT1 and SIRT3, and promotes a robust mitochondrial environment which favors reductions in oxidative stress and inflammation. To date, the literature examining R-βHB as a signaling metabolite has mostly been performed from endogenous R-βHB production achieved through nutritional ketosis or cell culture and mouse models using exogenous R-βHB. To the authors knowledge, only 1 study has attempted to report on the effects of exogenous ketones and the mitigation of oxidative stress/inflammation. Therefore, the scope of this review is to detail the mechanisms of R-βHB as a signaling metabolite and the role that exogenous ketones might play in mitigating diseases in individuals serving in high-stress occupations.

The Importance of Respiratory Rate Monitoring: From Healthcare to Sport and Exercise

Respiratory rate is a fundamental vital sign that is sensitive to different pathological conditions (e.g., adverse cardiac events, pneumonia, and clinical deterioration) and stressors, including emotional stress, cognitive load, heat, cold, physical effort, and exercise-induced fatigue. The sensitivity of respiratory rate to these conditions is superior compared to that of most of the other vital signs, and the abundance of suitable technological solutions measuring respiratory rate has important implications for healthcare, occupational settings, and sport. However, respiratory rate is still too often not routinely monitored in these fields of use. This review presents a multidisciplinary approach to respiratory monitoring, with the aim to improve the development and efficacy of respiratory monitoring services. We have identified thirteen monitoring goals where the use of the respiratory rate is invaluable, and for each of them we have described suitable sensors and techniques to monitor respiratory rate in specific measurement scenarios. We have also provided a physiological rationale corroborating the importance of respiratory rate monitoring and an original multidisciplinary framework for the development of respiratory monitoring services. This review is expected to advance the field of respiratory monitoring and favor synergies between different disciplines to accomplish this goal.

Active Shooter Training Drill Increases Blood and Salivary Markers of Stress

Police officers are frequently engaged in a variety of high-stress scenarios, such as high-speed chases and other suspect conflicts, that cause significant increases in a variety of physiological and psychological stress markers. The purpose of this study was to investigate salivary and blood markers of stress in response to an active shooter training drill (ASD). Thirty-one participants (n = 31; males = 15, females = 16; Age: 21 ± 3.5 years) participated in an ASD involving professional actors playing the role of one active gunman, as well as four victims. The ASD lasted approximately 50 s. Blood samples were collected 15 min prior as well as after the ASD and analyzed for epinephrine (EPI) and norepinephrine (NE) levels. Saliva samples were collected 30 and 5 min prior to the ASD and 5 and 30 min after the ASD, were analyzed for cortisol, α-amylase, and secretory immunoglobulin-A (SigA). The ASD resulted in significant (p < 0.05) increases in EPI, α-amylase, and SigA levels. The increase in NE from pre to post ASD approached significance (p = 0.06). These results demonstrate that a short duration (~50 s) ASD results in significant increases in both blood and salivary markers of stress. These data may provide meaningful implications for those engaged in high-stress tactical occupations, especially law enforcement and military personnel, as chronic exposure to such occupational stressors can contribute to cardiometabolic disease.

The Psychophysiological Determinants of Pacing Behaviour and Performance During Prolonged Endurance Exercise: A Performance Level and Competition Outcome Comparison

INTRODUCTION

A three-dimensional framework of centrally regulated and goal-directed exercise behaviour emphasised the integration of distinct sensory-discriminatory, affective-motivational and cognitive-evaluative dimensions that underpin perceived fatigability. This study aimed to capture the complex interdependencies and temporal dynamics in these processes, their interrelations with observed pacing behaviour, performance and biochemical variables as well as their performance level- and competition outcome-dependent variances.

METHODS

Twenty-three cyclists of distinct performance level categories engaged in individual and head-to-head competition time trials against a performance-matched opponent. Sensory, affective and cognitive processes were respectively assessed with the constructs perceived physical strain and perceived mental strain, valence and felt arousal underpinning core affect and action crisis characterised by a shift from an implemental to a deliberative mindset.

RESULTS

Performance level- and competition outcome-dependent variances and differential temporal dynamics in constructs were associated with alterations in pacing behaviour, performance and physiological disturbance. Perceived physical and mental strain were primarily associated with observed pacing behaviour as necessary to align planned behaviour with current physiological state. Valence and arousal were primarily associated with differential responses in performance regulation. The mindset shift associated with an action crisis was primarily associated with non-adaptive, psycho-neuro-endocrinological distress response.

CONCLUSION

The proposed constructs are interdependent in a nonlinear dynamic fashion, context dependent, constraint based, distinguishable by well-trained cyclists and interrelated with observed pacing behaviour, performance and physiological disturbance. The proposed framework provides a more comprehensive alternative to the Gestalt concept of perceived exertion and more completely accounts for centrally regulated and goal-directed exercise behaviour.

Effects of psychological stress during exercise on markers of oxidative stress in young healthy, trained men

PURPOSE

Those engaged in high stress occupations such as firefighters and military personnel are exposed to a variety of psychological and physiological stressors. The combination of mental and physical stress [i.e., dual stress challenges (DSC)] results in significant increases in stress hormones, which causes oxidative stress (OS) and contributes to elevated risk for cardiovascular disease. However, data are needed to determine the impact of DSC on markers of OS in exercise-trained individuals.

METHOD

Fourteen healthy trained men aged 21-30 yrs. participated in a randomized, cross-over design to investigate the impact of DSC on blood markers of OS. The exercise alone condition (EA) consisted of 35 min of cycling at 60% V̇O_{2 peak}. The DSC involved 20 min of mental stress challenges during exercise. Blood was sampled before exercise, as well as immediately, and 30 and 60 min after exercise and analyzed for glutathione (GSH), superoxide dismutase (SOD), hydrogen peroxide (H₂O₂) and advanced oxidation protein products (AOPP).

RESULT

No significant treatment × time interactions were found. No time effects were noted for SOD, or H₂O₂; however, AOPP were reduced at 30 (p = .034) and 60 min post exercise (p = .006). GSH was reduced at 30 (p = .009) and 60 min post exercise (p = .031).

CONCLUSION

These results indicate the OS response from DSC is not greater than that produced from EA in exercise trained men. Future work should investigate the impact of chronic resistance and endurance exercise training on OS resulting from DSC.

Ventilatory Responses During Submaximal Exercise in Children With Prader-Willi Syndrome

PURPOSE

Prader-Willi syndrome (PWS) is a genetic neurobehavioral disorder presenting hypothalamic dysfunction and adiposity. At rest, PWS exhibits hypoventilation with hypercapnia. We characterized ventilatory responses in children with PWS during exercise.

METHODS

Participants were children aged 7-12 years with PWS (n = 8) and without PWS with normal weight (NW; n = 9, body mass index ≤ 85th percentile) or obesity (n = 9, body mass index ≥ 95th percentile). Participants completed three 5-minute ambulatory bouts at 3.2, 4.0, and 4.8 km/h. Oxygen uptake, carbon dioxide output, ventilation, breathing frequency, and tidal volume were recorded.

RESULTS

PWS had slightly higher oxygen uptake (L/min) at 3.2 km/h [0.65 (0.46-1.01) vs 0.49 (0.34-0.83)] and at 4.8 km/h [0.89 (0.62-1.20) vs 0.63 (0.45-0.97)] than NW. PWS had higher ventilation (L/min) at 3.2 km/h [16.2 (13.0-26.5) vs 11.5 (8.4-17.5)], at 4.0 km/h [16.4 (13.9-27.9) vs 12.7 (10.3-19.5)], and at 4.8 km/h [19.7 (17.4-31.8) vs 15.2 (9.5-21.6)] than NW. PWS had greater breathing frequency (breaths/min) at 3.2 km/h [38 (29-53) vs 29 (22-35)], at 4.0 km/h [39 (29-58) vs 29 (23-39)], and at 4.8 km/h [39 (33-58) vs 32 (23-42)], but similar tidal volume and ventilation/carbon dioxide output to NW.

CONCLUSION

PWS did not show impaired ventilatory responses to exercise. Hyperventilation in PWS may relate to excessive neural stimulation and metabolic cost.

Modelling the process of falling behind and its psychophysiological consequences

INTRODUCTION

A preceding article investigated the psychophysiological responses to falling behind a performance matched opponent. The following temporally linked cause-effect relationships were hypothesised: falling behind precedes deterioration in valence, deterioration in valence precedes development of an action crisis, experience of an action crisis precedes psychoneuroendocrinological distress response and non-adaptive distress response reduces conduciveness to high performance, thereby preceding performance decrement.

METHODS

In this article, we applied structural equation modelling to test the extent to which the observed data fit the hypothesised cause-effect relationships. A five-step procedure was applied to model the interrelationships between the major study variables in the hypothesised temporal order.

RESULTS

Significant linear relationships were found between all hypothesised predictor and outcome variable pairs (p<0.024). The dynamic change in valence was a significant mediator (p=0.011) as it explained 35% of the relationship between falling behind and action crisis. All hypothesised cause-effect relationships continued to be significant after controlling for performance, descriptor, training and perceived strain variables. The observed data fitted the hypothesised structural model well with excellent model fit indices throughout.

CONCLUSION

We applied, tested and confirmed the hypothesised debilitative psychophysiological processes that unfold in response to falling behind a performance matched opponent. The main findings were: deterioration in valence mediated the relationship between falling behind and action crisis, the mindset shift associated with an action crisis predicted increased blood cortisol concentrations and non-adaptive blood cortisol concentrations predicted performance decrement. The findings point towards the crucial role of affective and cognitive modifiers in centrally regulated and goal-directed exercise behaviour.

Prior Acute Mental Exertion in Exercise and Sport

Introduction:

Mental exertion is a psychophysiological state caused by sustained and prolonged cognitive activity. The understanding of the possible effects of acute mental exertion on physical performance, and their physiological and psychological responses are of great importance for the performance of different occupations, such as military, construction workers, athletes (professional or recreational) or simply practicing regular exercise, since these occupations often combine physical and mental tasks while performing their activities. However, the effects of implementation of a cognitive task on responses to aerobic exercise and sports are poorly understood. Our narrative review aims to provide information on the current research related to the effects of prior acute mental fatigue on physical performance and their physiological and psychological responses associated with exercise and sports.

Methods:

The literature search was conducted using the databases PubMed, ISI Web of Knowledge and PsycInfo using the following terms and their combinations: “mental exertion”, “mental fatigue”, “mental fatigue and performance”, “mental exertion and sports” “mental exertion and exercise”.

Results:

We concluded that prior acute mental exertion affects effectively the physiological and psychophysiological responses during the cognitive task, and performance in exercise.

Conclusion:

Additional studies involving prior acute mental exertion, exercise/sports and physical performance still need to be carried out in order to analyze the physiological, psychophysiological and neurophysiological responses subsequently to acute mental exertion in order to identify cardiovascular factors, psychological, neuropsychological associates.

Stress Markers During a Rally Car Competition

The aim of the study was to assess the stress responses in drivers during an official rally car race and the influence of fitness and body composition on stress hormones. Fitness and body composition were assessed in 9 rally car drivers with an incremental exercise test for determination of maximum aerobic speed (MAS) and 6-site skinfold method, respectively. Before (pre) and after (post) the first stage of an official rally car race, data were collected for heart rate (HR), blood samples were collected for analysis of hormones (i.e., epinephrine [EPI], norepinephrine [NE], cortisol, and aldosterone) and metabolites (i.e., lactate [LA], glucose, and ammonia). There were significant (p ≤ 0.05) increases in all assessed variables except glucose at postrace. Heart rate increased 93% (p ≤ 0.05) at the end of the race stage, reaching 88.77 ± 4.96% of HRpeak. Also, EPI and NE significantly (p = 0.001) increased by 45 and 65%, respectively, and LA increased by 395% (p < 0.001). Significant correlations between percent body fat (%BF) and postrace EPI (r = 0.95; p < 0.001), and percentage change of EPI (r = 0.83; p = 0.012) were observed. The MAS was not associated to any metabolic or hormonal variable. These results suggest that psycho-physiological stress induced by the race elicited important changes in hormonal and metabolic variables and that %BF could be an important mediator of psycho-physiological stress in rally car drivers. Specific programs, including both strength and aerobic training, and nutritional plans should be implemented for appropriate conditioning of rally car drivers.

Lymphocyte glucose and glutamine metabolism as targets of the anti-inflammatory and immunomodulatory effects of exercise

Glucose and glutamine are important energetic and biosynthetic nutrients for T and B lymphocytes. These cells consume both nutrients at high rates in a function-dependent manner. In other words, the pathways that control lymphocyte function and survival directly control the glucose and glutamine metabolic pathways. Therefore, lymphocytes in different functional states reprogram their glucose and glutamine metabolism to balance their requirement for ATP and macromolecule production. The tight association between metabolism and function in these cells was suggested to introduce the possibility of several pathologies resulting from the inability of lymphocytes to meet their nutrient demands under a given condition. In fact, disruptions in lymphocyte metabolism and function have been observed in different inflammatory, metabolic, and autoimmune pathologies. Regular physical exercise and physical activity offer protection against several chronic pathologies, and this benefit has been associated with the anti-inflammatory and immunomodulatory effects of exercise/physical activity. Chronic exercise induces changes in lymphocyte functionality and substrate metabolism. In the present review, we discuss whether the beneficial effects of exercise on lymphocyte function in health and disease are associated with modulation of the glucose and glutamine metabolic pathways.

Cardiorespiratory fitness does not alter plasma pentraxin 3 and cortisol reactivity to acute psychological stress and exercise

Pentraxin 3 (PTX3) has been recently identified as a biomarker of vascular inflammation in predicting cardiovascular events. The purpose of this study was to examine the effect of cardiorespiratory fitness on plasma PTX3 and cortisol responses to stress, utilizing a dual-stress model. Fourteen male subjects were classified into high-fit (HF) and low-fit (LF) groups and completed 2 counterbalanced experimental conditions. The exercise-alone condition (EAC) consisted of cycling at 60% maximal oxygen uptake for 37 min, while the dual-stress condition (DSC) included 20 min of a mental stress while cycling for 37 min. Plasma PTX3 revealed significant increases over time with a significant elevation at 37 min in both HF and LF groups in response to EAC and DSC. No difference in plasma PTX3 levels was observed between EAC and DSC. In addition, plasma cortisol revealed a significant condition by time interaction with greater levels during DSC at 37 min, whereas cardiorespiratory fitness level did not reveal different plasma cortisol responses in either the EAC or DSC. Aerobic exercise induces plasma PTX3 release, while additional acute mental stress, in a dual-stress condition, does not exacerbate or further modulate the PTX3 response. Furthermore, cardiorespiratory fitness may not affect the stress reactivity of plasma PTX3 to physical and combined physical and psychological stressors. Finally, the exacerbated cortisol responses to combined stress may provide the potential link to biological pathways that explain changes in physiological homeostasis that may be associated with an increase in the risk of cardiovascular disease.

The effects of stress on physical activity and exercise

BACKGROUND

Psychological stress and physical activity (PA) are believed to be reciprocally related; however, most research examining the relationship between these constructs is devoted to the study of exercise and/or PA as an instrument to mitigate distress.

OBJECTIVE

The aim of this paper was to review the literature investigating the influence of stress on indicators of PA and exercise.

METHODS

A systematic search of Web of Science, PubMed, and SPORTDiscus was employed to find all relevant studies focusing on human participants. Search terms included "stress", "exercise", and "physical activity". A rating scale (0-9) modified for this study was utilized to assess the quality of all studies with multiple time points.

RESULTS

The literature search found 168 studies that examined the influence of stress on PA. Studies varied widely in their theoretical orientation and included perceived stress, distress, life events, job strain, role strain, and work-family conflict but not lifetime cumulative adversity. To more clearly address the question, prospective studies (n = 55) were considered for further review, the majority of which indicated that psychological stress predicts less PA (behavioral inhibition) and/or exercise or more sedentary behavior (76.4 %). Both objective (i.e., life events) and subjective (i.e., distress) measures of stress related to reduced PA. Prospective studies investigating the effects of objective markers of stress nearly all agreed (six of seven studies) that stress has a negative effect on PA. This was true for research examining (a) PA at periods of objectively varying levels of stress (i.e., final examinations vs. a control time point) and (b) chronically stressed populations (e.g., caregivers, parents of children with a cancer diagnosis) that were less likely to be active than controls over time. Studies examining older adults (>50 years), cohorts with both men and women, and larger sample sizes (n > 100) were more likely to show an inverse association. 85.7 % of higher-quality prospective research (≥ 7 on a 9-point scale) showed the same trend. Interestingly, some prospective studies (18.2 %) report evidence that PA was positively impacted by stress (behavioral activation). This should not be surprising as some individuals utilize exercise to cope with stress. Several other factors may moderate stress and PA relationships, such as stages of change for exercise. Habitually active individuals exercise more in the face of stress, and those in beginning stages exercise less. Consequently, stress may have a differential impact on exercise adoption, maintenance, and relapse. Preliminary evidence suggests that combining stress management programming with exercise interventions may allay stress-related reductions in PA, though rigorous testing of these techniques has yet to be produced.

CONCLUSIONS

Overall, the majority of the literature finds that the experience of stress impairs efforts to be physically active. Future work should center on the development of a theory explaining the mechanisms underlying the multifarious influences of stress on PA behaviors.

Cardiovascular reactivity, stress, and physical activity

Psychological stress has been proposed as a major contributor to the progression of cardiovascular disease (CVD). Acute mental stress can activate the sympathetic-adrenal-medullary (SAM) axis, eliciting the release of catecholamines (NE and EPI) resulting in the elevation of heart rate (HR) and blood pressure (BP). Combined stress (psychological and physical) can exacerbate these cardiovascular responses, which may partially contribute to the elevated risk of CVD and increased proportionate mortality risks experienced by some occupations (e.g., firefighting and law enforcement). Studies have supported the benefits of physical activity on physiological and psychological health, including the cardiovascular response to acute stress. Aerobically trained individuals exhibit lower sympathetic nervous system (e.g., HR) reactivity and enhanced cardiovascular efficiency (e.g., lower vascular reactivity and decreased recovery time) in response to physical and/or psychological stress. In addition, resistance training has been demonstrated to attenuate cardiovascular responses and improve mental health. This review will examine stress-induced cardiovascular reactivity and plausible explanations for how exercise training and physical fitness (aerobic and resistance exercise) can attenuate cardiovascular responses to stress. This enhanced functionality may facilitate a reduction in the incidence of stroke and myocardial infarction. Finally, this review will also address the interaction of obesity and physical activity on cardiovascular reactivity and CVD.

Aerobic fitness affects cortisol responses to concurrent challenges

PURPOSE

Studies have demonstrated that a combination of mental and physical challenge can elicit exacerbated state anxiety, effort sense, and cortisol responses above that of a single stimulus. However, an analysis of the effects of aerobic fitness on the responses of cortisol to concurrent mental and physical stress between below average and above average fitness individuals has not been conducted. This study examined the effects of a combination of acute mental challenges and physical stress on psychological and cortisol responses between eight individuals of below average fitness (low fit (LF), VO2max = 36.58 ± 3.36 mL·kg(-1)·min(-1)) and eight individuals of above average fitness (high fit (HF), VO2max = 51.18 ± 2.09 mL·kg(-1)·min).

METHODS

All participants completed two experimental conditions. An exercise-alone condition (EAC) consisted of cycling at 60% VO2max for 37 min, and a dual-challenge condition (DCC) included concurrent participation in a mental challenge for 20 min while cycling.

RESULTS

The DCC resulted in increases in state anxiety (P = 0.018), perceived overall workload (P = 0.001), and exacerbated cortisol responses (P = 0.04). Furthermore, LF participants had a greater overall cortisol response in the DCC compared with the EAC (DCC = 346.83 ± 226.92; EAC = -267.46 ± 132.32; t7 = 2.49, P = 0.04), whereas HF participants demonstrated no difference between conditions (DCC = 38.91 ± 147.01; EAC = -324.60 ± 182.78; t7 = 1.68, P = 0.14).

DISCUSSION

LF individuals seem to demonstrate unnecessary and unfavorable responses to the DCC compared with HF individuals, particularly concerning cortisol. The exacerbated cortisol responses in LF individuals have implications for harmful consequences such as increased risk of cardiovascular disease.

Occupational Stress

Occupational stress can affect physiological and psychological homeostasis. In addition, the occupational challenges associated with firefighting and law enforcement have been linked to increased mortality ratios for ischemic heart disease when compared with other population cohorts. Laboratory studies have shown that the exacerbation of stress hormones (eg, catecholamines) following dual challenge (physical and psychological stress) may affect immune system responses, which may partially explain the link between cardiovascular disease and inflammation. Physical fitness has been shown to attenuate both cardiovascular and inflammatory cytokine responses following physical and/or psychological stress; however, criteria for safe and effective occupation-specific fitness levels have not been established. In addition, firefighters and police officers have high overweight and obesity rates, which also contribute significantly to the development of cardiovascular disease. Future investigation on the possible interaction (additive or synergistic) of obesity and psychological stress on the development of cardiovascular diseases in these professions is warranted, and a criterion for fitness level should be established for safe and effective participation in occupation-related activities.

Psychological stress during exercise: immunoendocrine and oxidative responses

The purpose of this study was to examine the changes in catecholamines (epinephrine [EPI] and norepinephrine [NE]), interleukin-2 (IL-2) and a biomarker of oxidative stress (8-isoprostane) in healthy individuals who were exposed to a dual challenge (physical and psychological stress). Furthermore, this study also examined the possible relationships between catecholamines (NE and EPI) and 8-isoprostane and between IL-2 and 8-isoprostane following a combined physical and psychological challenge. Seven healthy male subjects completed two experimental conditions. The exercise-alone condition (EAC) consisted of cycling at 60% VO(2max) for 37 min, while the dual-stress condition (DSC) included 20 min of a mental challenge while cycling. DSC showed greater EPI and 8-isoprostane levels (significant condition by time interaction). NE and IL-2 revealed significant change across time in both conditions. In addition, following dual stress, EPI area-under-the-curve (AUC) demonstrated a positive correlation with NE AUC and IL-2 AUC. NE AUC was positively correlated with IL-2 AUC and peak 8-isoprostane, and peak IL-2 was positively correlated with peak 8-isoprostane in response to a dual stress. The potential explanation for elevated oxidative stress during dual stress may be through the effects of the release of catecholamines and IL-2. These findings may further provide the potential explanation that dual stress alters physiological homeostasis in many occupations including firefighting, military operations and law enforcement. A greater understanding of these responses to stress can assist in finding strategies (e.g. exercise training) to overcome the inherent psychobiological challenges associated with physically and mentally demanding professions.

Psychophysiological responses to different levels of cognitive and physical workload in haptic interaction

Psychophysiological measurements, which serve as objective indicators of psychological state, have recently been introduced into human–robot interaction. However, their usefulness in haptic interaction is uncertain, since they are influenced by physical workload. This study analyses psychophysiological responses to a haptic task with three different difficulty levels and two different levels of physical load. Four physiological responses were recorded: heart rate, skin conductance, respiratory rate and skin temperature. Results show that mean respiratory rate, respiratory rate variability and skin temperature show significant differences between difficulty levels regardless of physical load and can be used to estimate cognitive workload in haptic interaction.