Aerobic fitness affects cortisol responses to concurrent challenges

Physiological relationship between cardiorespiratory fitness and fitness for surgery: a narrative review

Epidemiological evidence has highlighted a strong relationship between cardiorespiratory fitness and surgical outcomes; specifically, fitter patients possess heightened resilience to withstand the surgical stress response. This narrative review draws on exercise and surgical physiology research to discuss and hypothesise the potential mechanisms by which higher fitness affords perioperative benefit. A higher fitness, as indicated by higher peak rate of oxygen consumption and ability to sustain metabolic homeostasis (i.e. higher anaerobic threshold) is beneficial postoperatively when metabolic demands are increased. However, the associated adaptations with higher fitness, and the related participation in regular exercise or physical activity, might also underpin the observed perioperative benefit through a process of hormesis, a protective adaptive response to the moderate and intermittent stress of exercise. Potential mediators discussed include greater antioxidant capacity, metabolic flexibility, glycaemic control, lean body mass, and improved mood.

Change in measures of moral function following acute bouts of Marine Corps Martial Arts Training

The Marine Corps Martial Arts Program (MCMAP) was developed to prepare Marines for complex battlefield situations that include hand-to-hand combat and ethical decision making. The objective of this study was to quantify changes in ethical decision-making following MCMAP training. Fifty-five, active duty, newly enlisted U.S. Marines (Males: n = 37; age = 19 ± 1 years; height = 176 ± 7 cm; mass = 74 ± 7 kg; Females: n = 18; age = 20 ± 2 years; height = 164 ± 6 cm; mass = 61 ± 6 kg) volunteered for this investigation and were assessed three times over 6 weeks, with 3 weeks between each visit, using serial blood samples for cortisol, norepinephrine, and epinephrine collected before training and during recovery [Immediate Post (IP), 15, 30, 45 and 60 min]. The Moral Functioning Continuum was used to quantify moral function before training, IP, 30, and 60 min post. Moral intention exhibited an acute response to training with significantly impaired decision making immediately post training. Moreover, both moral intention and moral judgement worsened over the visits suggesting a chronic impairment related to time in training suggesting a functional change in ethical decision-making following acute bouts of MCMAP.

Multimodal Benefits of Exercise in Patients With Multiple Sclerosis and COVID-19

Multiple sclerosis (MS) is a demyelinating disease characterized by plaque formation and neuroinflammation. The plaques can present in various locations, causing a variety of clinical symptoms in patients with MS. Coronavirus disease-2019 (COVID-19) is also associated with systemic inflammation and a cytokine storm which can cause plaque formation in several areas of the brain. These concurring events could exacerbate the disease burden of MS. We review the neuro-invasive properties of SARS-CoV-2 and the possible pathways for the entry of the virus into the central nervous system (CNS). Complications due to this viral infection are similar to those occurring in patients with MS. Conditions related to MS which make patients more susceptible to viral infection include inflammatory status, blood-brain barrier (BBB) permeability, function of CNS cells, and plaque formation. There are also psychoneurological and mood disorders associated with both MS and COVID-19 infections. Finally, we discuss the effects of exercise on peripheral and central inflammation, BBB integrity, glia and neural cells, and remyelination. We conclude that moderate exercise training prior or after infection with SARS-CoV-2 can produce health benefits in patients with MS patients, including reduced mortality and improved physical and mental health of patients with MS.

Association of Innate and Acquired Aerobic Capacity With Resilience in Healthy Adults: Protocol for a Randomized Controlled Trial of an 8-Week Web-Based Physical Exercise Intervention

BACKGROUND

Physical activity alleviates chronic stress. The latest research suggests a relationship between resilience and physical fitness. Beneficial adaptations of the hypothalamic-pituitary-adrenal axis, sympathetic nervous system, endocannabinoid system, and tryptophan pathway, which are induced by an active lifestyle, are considered to be conducive to resilience. However, detailed knowledge on the molecular link between the effects of acute and chronic physical exercise and improved resilience to stress in humans is missing. Moreover, the relationship between innate and acquired aerobic capacity and resilience is poorly understood.

OBJECTIVE

The aim of this study is to implement a human exercise intervention trial addressing the following main hypotheses: a high innate aerobic capacity is associated with high resilience to stress, and web-based physical exercise training improves aerobic capacity of physically inactive adults, which is accompanied by improved resilience. In this setting, we will analyze the relationship between resilience parameters and innate and acquired aerobic capacity as well as circulating signaling molecules.

METHODS

A total of 70 healthy, physically inactive (<150 minutes/week of physical activity) adults (aged 18-45 years) will be randomly assigned to an intervention or control group. Participants in the intervention group will receive weekly training using progressive endurance and interval running adapted individually to their remotely supervised home training performance via web-based coach support. A standardized incremental treadmill exercise test will be performed before and after the intervention period of 8 weeks to determine the innate and acquired aerobic capacity (peak oxygen uptake). Before and after the intervention, psychological tests and questionnaires that characterize parameters implicated in resilience will be applied. Blood and saliva will be sampled for the analysis of cortisol, lactate, endocannabinoids, catecholamines, kynurenic acid, and further circulating signal transducers. Statistical analysis will provide comprehensive knowledge on the relationship between aerobic capacity and resilience, as well as the capacity of peripheral factors to mediate the promoting effects of exercise on resilience.

RESULTS

The study was registered in October 2019, and enrollment began in September 2019. Of the 161 participants who were initially screened via a telephone survey, 43 (26.7%) fulfilled the inclusion criteria and were included in the study. Among the 55% (17/31) of participants in the intervention group and 45% (14/31) of participants in the control group who completed the study, no serious adverse incidents were reported. Of 43 participants, 4 (9%) withdrew during the program (for individual reasons) and 8 (19%) have not yet participated in the program; moreover, further study recruitment was paused for an indeterminate amount of time because of the COVID-19 pandemic.

CONCLUSIONS

Our study aims to further define the physiological characteristics of human resilience, and it may offer novel approaches for the prevention and therapy of mental disorders via an exercise prescription.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/29712.

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.

The Effects of Physical Exercise and Cognitive Training on Memory and Neurotrophic Factors

This study examined the combined effect of physical exercise and cognitive training on memory and neurotrophic factors in healthy, young adults. Ninety-five participants completed 6 weeks of exercise training, combined exercise and cognitive training, or no training (control). Both the exercise and combined training groups improved performance on a high-interference memory task, whereas the control group did not. In contrast, neither training group improved on general recognition performance, suggesting that exercise training selectively increases high-interference memory that may be linked to hippocampal function. Individuals who experienced greater fitness improvements from the exercise training (i.e., high responders to exercise) also had greater increases in the serum neurotrophic factors brain-derived neurotrophic factor and insulin-like growth factor-1. These high responders to exercise also had better high-interference memory performance as a result of the combined exercise and cognitive training compared with exercise alone, suggesting that potential synergistic effects might depend on the availability of neurotrophic factors. These findings are especially important, as memory benefits accrued from a relatively short intervention in high-functioning young adults.

Lifestyle Modulators of Neuroplasticity: How Physical Activity, Mental Engagement, and Diet Promote Cognitive Health during Aging

The number of the elderly across the globe will approximate 2.1 billion by 2050. Juxtaposed against this burgeoning segment of the population is evidence that nonpathological aging is associated with an increased risk for cognitive decline in a variety of domains, changes that can cause mild disability even before the onset of dementia. Given that pharmacological treatments that mitigate dementia are still outstanding, alternative therapeutic options are being investigated increasingly. The results from translational studies have shown that modifiable lifestyle factors-including physical activity, cognitive engagement, and diet-are a key strategy for maintaining brain health during aging. Indeed, a multiplicity of studies has demonstrated relationships between lifestyle factors, brain structure and function, and cognitive function in aging adults. For example, physical activity and diet modulate common neuroplasticity substrates (neurotrophic signaling, neurogenesis, inflammation, stress response, and antioxidant defense) in the brain whereas cognitive engagement enhances brain and cognitive reserve. The aims of this review are to evaluate the relationship between modifiable lifestyle factors, neuroplasticity, and optimal brain health during aging; to identify putative mechanisms that contribute positive brain aging; and to highlight future directions for scientists and clinicians. Undoubtedly, the translation of cutting-edge knowledge derived from the field of cognitive neuroscience will advance our understanding and enhance clinical treatment interventions as we endeavor to promote brain health during aging.

Physical Activity Modulates Common Neuroplasticity Substrates in Major Depressive and Bipolar Disorder

Mood disorders (MDs) are chronic, recurrent mental diseases that affect millions of individuals worldwide. Although the biogenic amine model has provided some clinical utility, a need remains to better understand the interrelated mechanisms that contribute to neuroplasticity deficits in MDs and the means by which various therapeutics mitigate them. Of those therapeutics being investigated, physical activity (PA) has shown clear and consistent promise. Accordingly, the aims of this review are to (1) explicate key modulators, processes, and interactions that impinge upon multiple susceptibility points to effectuate neuroplasticity deficits in MDs; (2) explore the putative mechanisms by which PA mitigates these features; (3) review protocols used to induce the positive effects of PA in MDs; and (4) highlight implications for clinicians and researchers.

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.

Acute bouts of exercise induce a suppressive effect on lymphocyte proliferation in human subjects: A meta-analysis

OBJECTIVE

Lymphocyte proliferative responses are commonly used to assess immune function in clinical settings, yet it is unclear how proliferative capacity is altered by exercise. This analysis aims to quantitatively assess the proliferative response of lymphocytes following an acute bout of exercise.

METHODS

Electronic databases were searched for articles containing the keywords "exercise" OR "acute" OR "aerobic" OR "resistance training" OR "immune function" AND "proliferation" AND "lymphocyte." Initial results yielded 517 articles of which 117 were reviewed in full. Twenty-four articles met the inclusion criteria. Calculated standardized mean difference (SMD) and corresponding standard errors (SE) were integrated using random-effect models.

RESULTS

Analyses uncovered evidence for suppression of proliferative capacity following acute exercise in general (SMD=-0.18, 95% CI: -0.21, -0.16) with long duration, high intensity exercise exhibiting a moderate suppressive effect (SMD=-0.55, 95% CI: -0.86, -0.24). Discordant proliferative responses for long duration, high intensity exercise in competitive versus non-competitive settings were identified with enhanced proliferation (SMD=0.46, 95% CI: 0.03, 0.89) observed following competitive events and a large suppressive effect detected for similar activities outside of a competitive environment (SMD: -1.28, 95% CI: -1.61, -0.96) (p=0.02).

CONCLUSION

Evidence suggests lymphocyte proliferation is suppressed following acute bouts of exercise, with exercise lasting longer than one hour having a greater magnitude of effect regardless of exercise intensity. Variations in observed effect sizes across intensity, duration, and competitive environment further highlight our need to acknowledge the impact of study designs in advancing our understanding of exercise immunology.

Exercise Enhances the Behavioral Responses to Acute Stress in an Animal Model of PTSD

INTRODUCTION

This study examined the effects of endurance exercise on the behavioral response to stress and patterns of brain-derived neurotrophic factor (BDNF), neuropeptide Y (NPY), and δ-opioid receptor (phospho-DOR) expression in the hippocampus.

METHODS

Animals ran on a treadmill at 15 m·min, 5 min·d gradually increasing to 20 min·d, 5 d·wk for 6 wk. After training, one group of animals was exposed to a predator scent stress (PSS) protocol for 10 min. Outcome measurements included behavior in an elevated plus-maze (EPM) and acoustic startle response (ASR) 7 d after exposure to stress. Immunohistochemical technique was used to detect the expression of the BDNF, NPY, and phospho-DOR in the hippocampus 8 d after exposure.

RESULTS

Sedentary animals exposed to PSS were observed to have a greater incidence of extreme behavior responses including higher anxiety, less total activity in the EPM, and greater amplitude in the ASR than unexposed and/or trained animals. Exercise-trained animals exposed to PSS developed a resiliency to the stress, reflected by significantly greater total activity in the EPM, reduced anxiety, and reduced ASR compared to the sedentary, exposed animals. Exercise in the absence of stress significantly elevated the expression of BDNF and phospho-DOR, whereas exposure to PSS resulted in a significant decline in the expression of NPY, BDNF, and phospho-DOR. Trained animals that were exposed maintained expression of BDNF, NPY, and phospho-DOR in most subregions of the hippocampus.

CONCLUSION

Results indicated that endurance training provided a mechanism to promote resilience and/or recovery from stress. In addition, exercise increased expression of BDNF, NPY, and DOR signaling in the hippocampus that was associated with the greater resiliency seen in the trained animals.

Hypothalamo-pituitary adrenal axis and sympatho-adrenal medullary system responses to psychological stress were not attenuated in women with elevated physical fitness levels

It is not clear if higher levels of cardiorespiratory fitness are associated with lower hypothalamo-pituitary adrenal (HPA) axis and sympatho-adrenal medullary (SAM) system reactivity to psychological stress in women. The association between cardio-metabolic risk markers and acute physiological responses to psychological stress in women who differ in their cardiorespiratory fitness status has also not been investigated. Women with high (n = 22) and low (n = 22) levels of fitness aged 30-50 years (in the mid-follicular phase of the menstrual cycle) were subjected to a Trier Social Stress Test (TSST) at 1500 h. Plasma concentrations of cortisol, adrenaline (Adr), noradrenaline (NA), and dopamine (DA) were measured in samples collected every 7-15 min from 1400 to 1700 h. Heart rate and blood pressure were measured at the same time points. Low-fit women had elevated serum triglyceride, cholesterol/HDL ratio, fasting glucose, and HOMA-IR levels compared with high-fit women. While cortisol, Adr, NA, HR, and blood pressure all demonstrated a significant response to the TSST, the responses of these variables did not differ significantly between high- and low-fit women in response to the TSST. Dopamine reactivity was significantly higher in the low-fit women compared with high-fit women. There was also a significant negative correlation between VO2 max and DA reactivity. These findings suggest that, for low-fit women aged 30-50 years, the response of HPA axis and SAM system to a potent acute psychological stressor is not compromised compared to that in high-fit women.

Cortisol, blood pressure, and heart rate responses to food intake were independent of physical fitness levels in women

This research tested the hypothesis that women who had higher levels of physical fitness will have lower hypothalamo-pituitary-adrenal axis (cortisol) and sympatho-adrenal medullary system (blood pressure and heart rate) responses to food intake compared with women who had low levels of physical fitness. Lower fitness (n = 22; maximal oxygen consumption = 27.4 ± 1.0 mL∙kg(-1)·min(-1)) and higher fitness (n = 22; maximal oxygen consumption = 41.9 ± 1.6 mL∙kg(-1)·min(-1)) women (aged 30-50 years; in the follicular phase of the menstrual cycle) who participated in levels of physical activity that met (lower fitness = 2.7 ± 0.5 h/week) or considerably exceeded (higher fitness = 7.1 ± 1.4 h/week) physical activity guidelines made their own lunch using standardised ingredients at 1200 h. Concentrations of cortisol were measured in blood samples collected every 15 min from 1145-1400 h. Blood pressures and heart rate were also measured every 15 min between 1145 h and 1400 h. The meal consumed by the participants consisted of 20% protein, 61% carbohydrates, and 19% fat. There was a significant overall response to lunch in all of the parameters measured (time effect for all, p < 0.01). The cortisol response to lunch was not significantly different between the groups (time × treatment, p = 0.882). Overall, both groups showed the same pattern of cortisol secretion (treatment p = 0.839). Systolic blood pressure, diastolic blood pressure, mean arterial pressure, or heart rate responses (time × treatment, p = 0.726, 0.898, 0.713, and 0.620, respectively) were also similar between higher and lower fitness women. Results suggest that the physiological response to food intake in women is quite resistant to modification by elevated physical fitness levels.

Identification of resilient individuals and those at risk for performance deficits under stress

Human task performance is affected by exposure to physiological and psychological stress. The ability to measure the physiological response to stressors and correlate that to task performance could be used to identify resilient individuals or those at risk for stress-related performance decrements. Accomplishing this prior to performance under severe stress or the development of clinical stress disorders could facilitate focused preparation such as tailoring training to individual needs. Here we measure the effects of stress on physiological response and performance through behavior, physiological sensors, and subjective ratings, and identify which individuals are at risk for stress-related performance decrements. Participants performed military-relevant training tasks under stress in a virtual environment, with autonomic and hypothalamic-pituitary-adrenal axis (HPA) reactivity analyzed. Self-reported stress, as well as physiological indices of stress, increased in the group pre-exposed to socioevaluative stress. Stress response was effectively captured via electrodermal and cardiovascular measures of heart rate and skin conductance level. A resilience classification algorithm was developed based upon physiological reactivity, which correlated with baseline unstressed physiological and self-reported stress values. Outliers were identified in the experimental group that had a significant mismatch between self-reported stress and salivary cortisol. Baseline stress measurements were predictive of individual resilience to stress, including the impact stress had on physiological reactivity and performance. Such an approach may have utility in identifying individuals at risk for problems performing under severe stress. Continuing work has focused on adapting this method for military personnel, and assessing the utility of various coping and decision-making strategies on performance and physiological stress.

Biological mechanisms underlying the role of physical fitness in health and resilience

Physical fitness, achieved through regular exercise and/or spontaneous physical activity, confers resilience by inducing positive psychological and physiological benefits, blunting stress reactivity, protecting against potentially adverse behavioural and metabolic consequences of stressful events and preventing many chronic diseases. In this review, we discuss the biological mechanisms underlying the beneficial effects of physical fitness on mental and physical health. Physical fitness appears to buffer against stress-related disease owing to its blunting/optimizing effects on hormonal stress responsive systems, such as the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. This blunting appears to contribute to reduced emotional, physiological and metabolic reactivity as well as increased positive mood and well-being. Another mechanism whereby regular exercise and/or physical fitness may confer resilience is through minimizing excessive inflammation. Chronic psychological stress, physical inactivity and abdominal adiposity have been associated with persistent, systemic, low-grade inflammation and exert adverse effects on mental and physical health. The anti-inflammatory effects of regular exercise/activity can promote behavioural and metabolic resilience, and protect against various chronic diseases associated with systemic inflammation. Moreover, exercise may benefit the brain by enhancing growth factor expression and neural plasticity, thereby contributing to improved mood and cognition. In summary, the mechanisms whereby physical fitness promotes increased resilience and well-being and positive psychological and physical health are diverse and complex.

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.

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.