Resistance training as an acute stressor in healthy young men: associations with heart rate variability, alpha-amylase, and cortisol levels

Digital phenotyping from heart rate dynamics: Identification of zero-poles models with data-driven evolutionary learning

Heart rate response to physical activity is widely investigated in clinical and training practice, as it provides information on a person's physical state. For emerging digital phenotyping approaches, there is a need for individualized model estimation. In this study, we propose a zero-poles model and a data-driven evolutionary learning method for identification. We also perform a comparison with existing first and second order models and gradient descent identification methods. The proposed model is based on a five-phase description of heart rate dynamics. Data was collected from 30 healthy participants using a treadmill and a thoracic sensor in two protocols (static and dynamic), for increasing and decreasing activity. Results show that the zero-poles model is a good fit for heart rate response to exercise (Pearson's coefficient ρ>.95), while first and second order models are also suitable (ρ>.92). The evolutionary learning method shows excellent results for fast model identification, in comparison with least-squares methods (p<.03). We surmise that the parameters of investigated linear dynamic models make good candidates for digital biomarkers and continuous monitoring.

Physiological Stress in Safer Cycling in Older Age (SiFAr-Stress): A Randomized Controlled Trial

One possibility for maintaining mobility in older age is cycling. We investigated the impact of the multicomponent "Safer Cycling in Older Age" (SiFAr) intervention on psychological and physiological stress. Participants were 98 community-dwelling older adults (73.4 ± 5.4 years). Bedtime cortisol, hair cortisol concentrations, and C-reactive protein were measured before and after the 8-week SiFAr intervention and at follow-up. Additionally, acute stress responses were assessed during the second and seventh training sessions using salivary alpha-amylase and cortisol assessments. We found a decrease in acute perceived stress, anxiety, fear of falling, and uncertainty during the cycling trainings. Moreover, long-term perceived stress significantly decreased. No significant changes were found for any of the physiological stress measures. We conclude that cycling had a positive impact on perceived stress and wellbeing. Further research with more intense trainings is needed to fully understand the associations between cycling in older age and physiological stress.

Subjective and objective stress during body exposure: a comparison of adolescents with anorexia nervosa versus high body dissatisfaction

Objective

Body dissatisfaction (BD) is a risk factor for the development of an eating disorder (ED) and a negative predictor for treatment outcome in adolescents with anorexia nervosa (AN). As a clinical core symptom and a relevant maintaining factor of AN, body image disturbance and BD are highly relevant target variables for therapeutic interventions. Body exposure (BE) was found as being effective for reducing BD in adolescents with EDs and high BD. However, the underlying mechanisms of BE are still not clear, with habituation processes being discussed as one possible mechanism.

Methods

Affective and neurobiological processes during a four-session computer-based BE intervention were investigated. Within a controlled design comparing adolescents with AN (n = 34) vs. adolescent patients with high BD (n = 17) but without a diagnosed ED, subjective (stress ratings; 11-point Likert scale) and objective (salivary cortisol and alpha-amylase [sAA]) stress measures were assessed at four time points at each exposure session (start, +10 min, +30 min/end, +60 min/recovery). ED and depressive psychopathology were assessed via self-rating questionnaires.

Results

A between-session habituation effect was found for subjective stress ratings and sAA levels with decreasing scores throughout the four sessions. A within-session habituation was found for cortisol levels. Higher psychopathology was associated with subjective stress ratings. There were no group differences between AN and BD regarding ED psychopathology or subjective or objective stress measures. Subjective and objective stress measures were mainly not associated with each other.

Conclusions

Habituation processes were found for subjective and objective stress, which might enhance motivation to continue BE interventions and thus increase their impact. BD seems to be a transdiagnostic phenomenon with BE as a successful intervention independent of psychiatric diagnosis. Current findings should be validated in larger samples, and the hypothesis of a transdiagnostic BD should be investigated in future research.

Impact of the TTN C > T Polymorphism on Selected Variables of Aerobic and Anaerobic Capacity after a 12-Week Training Program

The TTN gene encodes a large muscle protein called titin, which provides structure, stability, and flexibility to skeletal and cardiac sarcomeres. The aim of this study was to determine whether the TTN C > T polymorphism (rs10497520) influenced training-induced changes in selected variables of aerobic and anaerobic capacity. We studied genotypes distribution in a group of 156 Caucasian females examined for aerobic capacity evaluated by maximal oxygen uptake (VO2max), and anaerobic capacity measured with the Wingate anaerobic test, before and after a 12-week training program. The most important finding was a genotype by training interaction for anaerobic capacity (AnC) during the Wingate test (p = 0.003). In response to training, carriers of the CT and TT genotypes demonstrated a significant increase in the total amount of work accomplished. We also showed that the applied training program improved all the Wingate test variables in the CT + TT genotype group by 10%. The obtained results suggest that the CT and TT genotypes may enhance anaerobic power and anaerobic capacity changes induced by regular training. We also suggest that T allele carriers may possess a metabolic adaptive advantage towards the anaerobic metabolism. Thus, the TTN gene may be considered a promising marker used in sports science, underlying variability in achieving sporting goals in events where the anaerobic energy system predominates.

Association between different types of physical activity and occupational stress in Japanese workers: a cross-sectional study

This cross-sectional study investigated the association between different types of physical activity (PA) and occupational psychological and physical stress responses among workers in Japan. Stress responses were assessed using the Brief Job Stress Questionnaire. Work-related PA (time spent sitting, sitting bouts, standing, walking, engaging in heavy labor, and moderate-to-vigorous PA [MVPA]) and exercise-based PA (frequencies [times/week] of flexibility and muscle-strengthening activity, and walking) were measured using a questionnaire. Multiple linear regression was performed to examine the association between each type of PA and stress responses. Participants who engaged in >108 min/day of work-related MVPA exhibited a statistically significant association with higher psychological stress responses when compared to those who engaged in 0-42 min/day of work-related MVPA. For exercise-based PA, participants who engaged in flexibility activity or walking five or more times/week, or muscle-strengthening activity one to three times/week, demonstrated significantly lower psychological stress responses compared to those who did not exercise. Participants who engaged in flexibility activity five or more times/week demonstrated significantly lower physical stress responses compared to those who did not exercise. This study suggests that work-related MVPA is associated with higher psychological stress responses, while exercise-based PA is associated with lower psychological or physical stress responses.

A comprehensive study of the academic benefits and practical recommendations to include resistance training programs in institutional education

The connection between physical activity and cognitive function has become a focus of attention in educational research in recent years. Regular exercise has been shown to have significant positive effects on physical health, but it also appears to have a significant impact on cognitive function and academic performance. Of all the exercise modalities, resistance training has drawn interest for its ability to improve cerebral abilities in addition to physical well-being. However, there is limited available knowledge exploring the relationship between resistance training regimens and academic performance. This narrative review aims to investigate the underlying mechanisms linking resistance training to academic performance. Firstly, we will examine the biological mechanisms and psychosocial links that potentially connect resistance training to academic performance to find and describe the different mechanisms by which resistance training improves academic performance. In the next part of the work, we delve into the existing observational and intervention studies that have explored the relationship between resistance training and academic performance. Lastly, we provide practical recommendations for including resistance training in institutional education settings, emphasizing the need of dispelling myths and addressing barriers to increase participation as well as the relevance of considering key training variables and adaptation of protocols to developmental stages, always guided by a properly trained professional. Overall, the available evidence supports that resistance training provides potential benefits to the academic performance of youth students with many biological and psychosocial factors that explain this relationship. However, most of the studies are observational, and broader interventional studies are needed to understand and maximize the benefits of this type of physical exercise.

Combined associations of regular exercise and work-related moderate-to-vigorous physical activity with occupational stress responses: a cross-sectional study

Objective

The association between work-related moderate-to-vigorous physical activity (MVPA) and higher levels of stress response is recognized, but whether this association is moderated by regular exercise remains unclear. This cross-sectional study investigated whether exercise-based physical activity (PA) associates with lower levels of stress responses moderated by work-related MVPA.

Methods

The study participants comprised 863 workers from 35 small and medium-sized enterprises in Shimane prefecture, Japan, collected through convenient sampling from April 2021 to August 2022. The Brief Job Stress Questionnaire was used to assess stress responses. Work-related MVPA and exercise-based PA were measured using questionnaires. Multiple linear regression was used to analyze the combined variables of work-related MVPA and exercise-based PA. The reference group had no weekly exercise-based PA and >60 min of work-related MVPA.

Results

When work-related MVPA exceeded 60 min/day, flexibility activity or walking for ≥5 days/week (B = -3.53, 95% CI = -5.96, -1.11; B = -2.53, 95% CI = -4.90, -0.16) and muscle-strengthening activity 1-3 times/week (B = -3.52, 95% CI = -6.91, -0.12) were significantly associated with lower psychological stress response. Flexibility activity (B = -1.74, 95% CI = -3.01, -0.46) showed a similar link with physical stress response. When work-related MVPA was below 60 min/day, flexibility activity (B = -3.23, 95% CI = -6.01, -0.44; B = -3.29, 95% CI = -5.94, -0.63) or walking (B = -4.03, 95% CI = -6.62, -1.45; B = -3.10, 95% CI = -5.76, -0.44) practice 1-4 times/week and ≥5 times/week was significantly associated with lower psychological stress response.

Conclusion

Exercise-based PA greatly and consistently associates with a lower level of stress responses moderated by work-related MVPA.

Deloading Practices in Strength and Physique Sports: A Cross-sectional Survey

BACKGROUND

This study explored the deloading practices of competitive strength and physique athletes. A 55-item anonymised web-based survey was distributed to a convenience-based, cross-sectional sample of competitive strength and physique athletes (n = 246; males = 181 [73.6%], females = 65 [26.4%]; age = 29.5 ± 8.6 years) who had 8.2 ± 6.2 years of resistance training and 3.8 ± 3.1 years of competition experience.

RESULTS

All athletes deloaded within training with energy and fatigue management being the main reasons to do so. The typical duration of a deload was 6.4 ± 1.7 days, integrated into the training programme every 5.6 ± 2.3 weeks. Deloading was undertaken using a proactive, pre-planned strategy (or in combination with an autoregulated approach) and undertaken when performance stalled or during periods of increased muscle soreness or joint aches. Athletes reported that training volume would decrease (through a reduction in both repetitions per set and sets per week), but training frequency would remain unchanged during deloads. Additionally, athletes reported that training intensity (load lifted) would decrease, and effort would be reduced (facilitated through an increase in repetitions in reserve). Athletes would generally maintain the same exercise selection during deloading. For athletes that supplemented deloading with additional recovery modalities (n = 118; 48%), the most reported strategies were massage, static stretching and foam rolling.

CONCLUSION

Results from this research might assist strength and physique athletes and coaches to plan their deloading. Future research should empirically investigate the findings from this study to further evaluate the potential utility of deloading in strength and physique sports.

Can you smell my stress? Influence of stress chemosignals on empathy and emotion recognition in depressed individuals and healthy controls

Human body odors contain chemical signals that play a key role in our non-verbal communication regarding health, genetic identity, immune system, fitness, and emotional state. Studies on human chemosignaling in individuals with psychiatric diseases are scarce but indicate altered smell perception and emotion recognition in depressed individuals. In the present project, we aimed to investigate the influence of chemosensory substances in social stress sweat on emotion recognition, perspective taking, affective responsiveness as well as stress level in healthy and depressed individuals. Therefore, chemosensory stimuli (sweat samples from Trier social stress test (TSST) and friendly-TSST (fTSST)) were obtained from 39 healthy participants (19 females). In a next step, chemosensory stimuli and an odor-free blank (cotton pad) were used to stimulate another group of 40 healthy participants (20 females) and 37 individuals with depression (24 females). Those stimuli were examined regarding their influence on subjective feelings of stress, emotion perception and empathic reactions using an empathy test. Furthermore, physiological data (breathing, heart rate, skin conductance response, stress hormones) of the participants were collected during chemosensory stimulation. Depressed individuals improved their ability of perspective taking and affective responsiveness for the emotion grief when presented with stress chemosignals compared to no chemosignals. Healthy individuals remained unaffected regarding perspective taking and affective responsiveness. Both depressed and healthy individuals showed no increased stress hormone cortisol and α-amylase values during the social stress chemosignals condition, but reduced values for fTSST condition compared to no chemosignals respectively. The results imply that stress chemosignals do not trigger a stress reaction, but for depressed individuals they lead to a better emotion assessment for grief. This research contributes to a deeper understanding of the effects of social stress chemosignals on healthy and depressed individuals. Knowing the impact of human chemosignals on emotional processing is crucial for a better understanding of non-verbal human interaction.

Acute Social Stress Influences Moral Decision-Making Under Different Social Distances in Young Healthy Men

Acute social stress has been shown to influence social decision-making. This study aimed to examine how social distance modulates the influence of acute social stress on young male moral decision-making. Sixty healthy male college students were randomly divided to be exposed to the Trier Social Stress Test (TSST) or a placebo version of the TSST (P-TSST) before they performed moral decision-making tasks. The results showed that participants under acute social stress showed obvious increases in subjective stress perception, negative affect, salivary cortisol, and alpha-amylase and made more altruistic choices for others compared to the control group. However, social distance regulates the promotion of this acute social stress, with the promotion effect being stronger in socially distant others. Furthermore, the interpersonal order difference of different social distances in altruistic decisions is smaller in low-conflict dilemmas than in high-conflict dilemmas. In addition, an increase in salivary cortisol was positively correlated with altruistic choices toward both acquaintances and strangers, whereas an increase in salivary alpha-amylase was only positively correlated with altruistic choices toward friends. The results suggest that social distance modulates the promotion of acute social stress on moral decision-making, which might stem from the divergent effects of cortisol and alpha-amylase.

Resistance exercise with different workloads have distinct effects on cellular respiration of peripheral blood mononuclear cells

Little is known how acute exercise-induced inflammation and metabolic stress affect immune cell bioenergetics and the portion of its components. Therefore, we investigated acute effects of eccentric-only (E), concentric-only (C) and combined eccentric-concentric resistance exercise (E + C) bouts on cellular respiration of peripheral blood mononuclear cells (PBMCs). Twelve strength-trained young men performed bench press resistance exercises in randomized order. Venous blood samples were drawn at pre-, 5 min post- and 24 h post-exercise. Several PBMC respiration states were measured using high-resolution respirometry. Levels of leukocytes, interleukin 6 (IL-6), C-reactive protein (CRP), creatine kinase (CK), blood lactate and maximum voluntary isometric force were measured from the same time points. Effects of blood lactate and pH change on bioenergetics of PBMCs were investigated ex vivo. PBMC routine respiration (p = 0.017), free routine capacity (p = 0.025) and ET-capacity (p = 0.038) decreased immediately after E + C. E responded in opposite manner 5 min post-exercise compared to E + C (p = 0.013) and C (p = 0.032) in routine respiration, and to E + C in free routine activity (p = 0.013). E + C > C > E was observed for increased lactate levels and decreased isometric force that correlated with routine respiration (R = -0.369, p = 0.035; R = 0.352, p = 0.048). Lactate and pH change did not affect bioenergetics of PBMCs. Acute resistance exercise affected cellular respiration of PBMCs, with training volume and the amount of metabolic stress appear influential. Results suggest that acute inflammation response does not contribute to changes seen in cellular respiration, but the level of peripheral muscle fatigue and metabolic stress could be explaining factors.

Differences in stress system (re-)activity between single and dual- or multitasking in healthy adults: A systematic review and meta-analysis

AbstractIn the age of digitization, multitasking requirements are ubiquitous, especially in the workplace. Multitasking (MT) describes the activity of performing multiple (at least two) tasks at the same time. Dual tasking (DT) refers to the sequential switching between two tasks. The aim of our systematic review and meta-analysis was first to investigate whether physiological stress systems become activated in response to or during MT/DT and, secondly, whether this (re-)activity is higher compared to single tasking. We focused on the Sympathetic Nervous System (SNS), the Parasympathetic Nervous System (PNS), the hypothalamic-pituitary adrenal (HPA) axis, and the immune system. The systematic review has been pre-registered with PROSPERO (CRD42020181415). A total of twenty-five articles were identified as eligible, in which n = 26 studies were reported, with N = 1,142 participants. Our main findings are that SNS activity is significantly higher and PNS activity is significantly lower during MT/DT than during single tasking. Only two studies were found, in which HPA axis (re-)activity was surveyed. No eligible study was identified in which immune system (re-)activity was investigated. This is the first systematic synthesis of the literature base showing that stress system activity is increased during MT/DT in comparison to single-tasking.

Higher Peripheral Inflammation Is Associated With Lower Orbitofrontal Gamma Power in Chronic Tinnitus

Chronic tinnitus, the continuous perception of a phantom sound, is a highly prevalent audiological symptom, for which the underlying pathology has not yet been fully understood. It is associated with neurophysiological alterations in the central nervous system and chronic stress, which can be related with a disinhibition of the inflammatory system. We here investigated the association between resting-state oscillatory activity assessed with Magnetoencephalography (MEG), and peripheral inflammation assessed by C-reactive protein (CRP) in a group of patients with chronic tinnitus (N = 21, nine males, mean age: 40.6 ± 14.6 years). Additionally, CRP was assessed in an age- and sex-matched healthy control group (N = 21, nine males, mean age: 40.9 ± 15.2 years). No MEG data was available for the control group. We found a significant negative correlation between CRP and gamma power in the orbitofrontal cortex in tinnitus patients (p < 0.001), pointing to a deactivation of the orbitofrontal cortex when CRP was high. No significant clusters were found for other frequency bands. Moreover, CRP levels were significantly higher in the tinnitus group than in the healthy controls (p = 0.045). Our results can be interpreted based on findings from previous studies having disclosed the orbitofrontal cortex as part of the tinnitus distress network. We suggest that higher CRP levels and the associated deactivation of the orbitofrontal cortex in chronic tinnitus patients is maintaining the tinnitus percept through disinhibition of the auditory cortex and attentional or emotional top-down processes. Although the direction of the association (i.e., causation) between CRP levels and orbitofrontal gamma power in chronic tinnitus is not yet known, inflammation reducing interventions are promising candidates when developing treatments for tinnitus patients. Overall, our study highlights the importance of considering immune-brain communication in tinnitus research.

An examination of physical activity guidelines and health-related quality of life among U.S. older adults

Physical activity can help improve the poor health-related quality of life in older adult population. Although the Physical Activity Guidelines for Americans recommend both aerobic and muscle strengthening activities for adults, previous studies predominantly focused on aerobic activity with limited research on muscle strengthening activities. The purpose of this cross-sectional study was to examine the relationships between meeting physical activity guidelines (i.e., aerobic activity, muscle strengthening activity) and health-related quality of life in the older adult population. Data of 87,495 older adults aged ≥65 years from the U.S. 2019 Behavioral Risk Factor Surveillance System were analyzed. Phone interviews and validated questionnaires were used to assess aerobic activity, muscle strengthening activity, and health-related quality of life. Binomial logistic regression was used to examine the relationships between meeting physical activity guidelines and health-related quality of life while adjusting for key covariates (i.e., age, sex, race, education, marital status, employment status, income, body mass index, smoking, drinking, and comorbidities). Participants meeting both or aerobic activity guideline only had significantly lower odds of reporting all components of health-related quality of life (i.e., general health, mental health, physical health, activity limitation) than those who met neither guideline (OR = 0.37-0.58) and those who met muscle strengthening activity guideline only (OR = 0.34 - 0.74). Given the stronger positive association between aerobic activity and health-related quality of life than that between muscle strengthening activity and health-related quality of life, future research should focus on promoting aerobic activity to increase health-related quality of life among older people.

Physiological stress in response to multitasking and work interruptions: Study protocol

BACKGROUND

The biopsychological response patterns to digital stress have been sparsely investigated so far. Important potential stressors in modern working environments due to increased digitalization are multitasking and work interruptions. In this study protocol, we present a protocol for a laboratory experiment, in which we will investigate the biopsychological stress response patterns to multitasking and work interruptions.

METHODS

In total, N = 192 healthy, adult participants will be assigned to six experimental conditions in a randomized order (one single-task, three dual-task (two in parallel and one as interruption), one multitasking, and one passive control condition). Salivary alpha-amylase as well as heart rate as markers for Sympathetic Nervous System Activity, heart rate variability as measure for Parasympathetic Nervous System (PNS) activity, and cortisol as measure for activity of the hypothalamic-pituitary adrenal (HPA) axis will be assessed at six time points throughout the experimental session. Furthermore, inflammatory markers (i.e., IL-6, C-reactive protein (CRP), and secretory immunoglobulin-A) will be assessed before and after the task as well as 24 hours after it (IL-6 and CRP only). Main outcomes will be the time course of these physiological stress markers. Reactivity of these measures will be compared between the experimental conditions (dual-tasking, work interruptions, and multitasking) with the control conditions (single-tasking and passive control).

DISCUSSION

With this study protocol, we present a comprehensive experiment, which will enable an extensive investigation of physiological stress-responses to multitasking and work interruptions. Our planned study will contribute to a better understanding of physiological response patterns to modern (digital) stressors. Potential risks and limitations are discussed. The findings will have important implications, especially in the context of digital health in modern working and living environments.

Effects of Mixed of a Ketogenic Diet in Overweight and Obese Women with Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a commonly occurring endocrine disorder characterized by hirsutism, anovulation, and polycystic ovaries. Often comorbid with insulin resistance, dyslipidemia, and obesity, it also carries significant risk for the development of cardiovascular and metabolic sequelae, including diabetes and metabolic syndrome. The relationship between central obesity and the development of insulin resistance is widely verified. Adipose tissue excess and the coexistent dysregulation of adipocyte functions directly contribute to the pathogenesis of the metabolic complications observed in women with PCOS. In the light of these evidence, the most therapeutic option prescribed to obese women with PCOS, regardless of the phenotype e from the severity of clinical expression, is lifestyle correction by diet and physical activity. The aim of this study is to evaluate the beneficial effects of ketogenic diet in 17 obese women with PCOS. Our results showed that the ketogenic diet inducing therapeutic ketosis, improves the anthropometric and many biochemical parameters such as LH, FSH, SHBG, insulin sensitivity and HOMA index. In addition, it induces a reduction in androgenic production, whereas the contextual reduction of fat mass reduced the acyclic production of estrogens deriving from the aromatization in the adipose tissue of the androgenic excess, with an improvement of the LH/FSH ratio. This is the first study on the effects of the ketogenic diet on PCOS, however, further studies are needed to elucidate the mechanism underlying ketogenic diet effects.

The impact of resistance training on body composition, muscle strength, and functional fitness in older women (45-80 years): A systematic review (2010-2020)

As women age, they typically experience a progressive decrease in skeletal muscle mass and strength, which can lead to a decline in functional fitness and quality of life. Resistance training (RT) has the potential to attenuate these losses. Although well established for men, evidence regarding the benefits of RT for women is sparse and inconsistent: prior reviews include too few studies with women and do not adequately examine the interactive or additive impacts of workload, modalities, and nutritional supplements on outcomes such as muscle mass (MM), body composition (BC), muscle strength (MS), and functional fitness (FF). The purpose of this review is to identify these gaps. Thirty-eight papers published between 2010 and 2020 (in English) represent 2519 subjects (mean age = 66.89 ± 4.91 years). Intervention averages include 2 to 3 × 50 min sessions across 15 weeks with 7 exercises per session and 11 repetitions per set. Twelve studies (32%) examined the impact of RT plus dietary manipulation. MM, MS, and FF showed positive changes after RT. Adding RT to fitness regimens for peri- to postmenopausal women is likely to have positive benefits.

Physiological stress in safer cycling in older age (SiFAr-stress): effect of a multicomponent exercise intervention-a study protocol for a randomized controlled trial

BACKGROUND

SiFAr-Stress investigates the impact of cycling on stress levels in older adults. Uncertainty due to change to motorized bicycle or fear of falling can be perceived as stressors for cyclists. Stress activates different physiological signal cascades and stimulates the hypothalamic-pituitary-adrenal (HPA) axis, which leads to the release of the stress hormone cortisol and further effects such as the development of low-grade inflammation. Both can-in the long term-be associated with negative health outcomes. The aim of the study SiFAr-Stress is to analyze inflammatory processes as well as the activity of stress systems before and after a cycling intervention for older adults.

METHODS

In this study, community-dwelling older adults aged 65 years and older will be randomly assigned to either a cycling or a control intervention in a parallel-group design. Objective HPA axis-related measures (saliva cortisol and hair cortisol) will be assessed before, after, and 6-9 months after the cycling and control intervention (T0, T1, and T2). Furthermore, changes in cortisol reactivity in response to the cycling intervention will be investigated at the second and seventh training lessons. Furthermore, secondary outcomes (fear of falling, perceived stress, salivary alpha amylase, and C-reactive protein) will be assessed at T0, T1, and T2.

DISCUSSION

The study will be the first, in which stress- and health-related bio-physiological outcomes will be assessed in the context of a multicomponent exercise intervention, addressing cycling in older adults. It will enable us to better understand the underlying patho-physiological and psychological mechanisms and will help to improve interventions for this target group.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04362514 . Prospectively registered on 27 April 2020.

Very Low-Calorie Ketogenic Diet Modulates the Autonomic Nervous System Activity through Salivary Amylase in Obese Population Subjects

In obesity, to reduce visceral adipose tissue (VAT), caloric restriction is a valid strategy. Salivary amylase is an enzyme that cleaves large starch carbohydrates molecules and its production is modulated by the central nervous system. In addition, heart rate variability (HRV) is simply a measure of the variation in time between each heartbeat. This variation is controlled by the autonomic nervous system. In the light of this evidence, the aim of this study is to characterize the effect of a very low-calorie ketogenic diet (VLCKD) on the autonomic nervous system in obese patients. Twenty subjects affected by obesity were recruited before and after 8 weeks of VLCKD intervention to evaluate salivary amylase by the ELISA test and HRV analysis. These parameters significantly increased after dietary treatment, and positively correlate to each other. VLCKD exerts a positive effect on salivary amylase and HRV, ameliorating body composition and biochemical features. In brief, this dietary intervention improves the autonomic nervous system activity. This is the first study about the effects of VLCKD upon the autonomic nervous system, but further studies are needed to elucidate the mechanism undergone VLCKD effects.

Physical Activity as a Treatment for Social Anxiety in Clinical and Non-clinical Populations: A Systematic Review and Three Meta-Analyses for Different Study Designs

The fear of being in the focus of attention in social situations can develop into a social anxiety disorder (SAD). The classical treatment for SAD is cognitive behavioral therapy, which is in many cases accompanied by drug treatments. A promising alternative treatment is physical activity (PA) interventions, because regular PA has been shown to be suitable for reducing anxiety in general. We conducted a pre-registered systematic review and meta-analysis (PROSPERO registration no. CRD42020191181) as well as two additional searches. Our aim was to investigate whether PA interventions are a suitable treatment for SAD and whether PA is suitable for reducing social anxiety (SA) in general. For studies with randomized controlled trial designs, a not statistically significant effect of medium size toward lower general SA symptomatology was found in the PA group in comparison with the control group (d = -0.24, p = 0.377). For studies with longitudinal designs, significantly lower SA symptoms were found after PA treatments (d = -0.22, p = 0.001). The effect of PA on SA was stronger for adults than for children and adolescents (p = 0.003). For cross-sectional studies, a small negative association between SA symptoms and the amount of PA was found, i.e., lower SA was found for people who were more physically active (r = -0.12, p = 0.003). We conclude that PA is a promising means for the (additional) treatment of SAD or to reduce SA in general in non-clinical samples, but more research in which high-quality studies with randomized controlled trial designs are used is needed. Furthermore, open questions with respect to moderating variables (e.g., age, sex, BMI, type of intervention, stress, amount of regular PA before the intervention, and comorbidities) remain still open.