Maximal oxygen uptake prediction from submaximal bicycle ergometry using a differential model.

The maximal oxygen uptake (VO2max) estimation has been a subject of research for many years. Cardiorespiratory measurements during incremental tests until exhaustion are considered the golden yard stick to assess VO2max. However, precise VO2max determination based on submaximal tests is attractive for athlete as well for clinical populations. Here, we propose and verify such a method based on experimental data. Using a recently developed model of heart rate (HR) and VO2 kinetics in graded exercise tests, we applied a protocol, which is terminated at 80% of the estimated maximal HR during ergometer cycling. In our approach, initially, formula for maximal HR is selected by retrospective study of a reference population (17 males, 23.5 ± 2.0 years, BMI: 23.9 ± 3.2 kg/m2). Next, the subjects for experimental group were invited (nine subjects of both sexes: 25.1 ± 2.1 years, BMI 23.2 ± 2.2 kg/m2). After calculation of maximal HR using cardiorespiratory recordings from the submaximal test, VO2max is predicted. Finally, we compared the prediction with the values from the maximal exercise test. The differences were quantified by relative errors, which vary from 1.2% up to 13.4%. Some future improvements for the procedure of VO2max prediction are discussed. The experimental protocol may be useful for application in rehabilitation assessment and in certain training monitoring settings, since physical exertion is not a prerequisite and the approach provides an acceptable VO2max estimation accuracy.

Fatigue and Human Performance: An Updated Framework.

Fatigue has been defined differently in the literature depending on the field of research. The inconsistent use of the term fatigue complicated scientific communication, thereby limiting progress towards a more in-depth understanding of the phenomenon. Therefore, Enoka and Duchateau (Med Sci Sports Exerc 48:2228-38, 2016, [3]) proposed a fatigue framework that distinguishes between trait fatigue (i.e., fatigue experienced by an individual over a longer period of time) and motor or cognitive task-induced state fatigue (i.e., self-reported disabling symptom derived from the two interdependent attributes performance fatigability and perceived fatigability). Thereby, performance fatigability describes a decrease in an objective performance measure, while perceived fatigability refers to the sensations that regulate the integrity of the performer. Although this framework served as a good starting point to unravel the psychophysiology of fatigue, several important aspects were not included and the interdependence of the mechanisms driving performance fatigability and perceived fatigability were not comprehensively discussed. Therefore, the present narrative review aimed to (1) update the fatigue framework suggested by Enoka and Duchateau (Med Sci Sports Exerc 48:2228-38, 2016, [3]) pertaining the taxonomy (i.e., cognitive performance fatigue and perceived cognitive fatigue were added) and important determinants that were not considered previously (e.g., effort perception, affective valence, self-regulation), (2) discuss the mechanisms underlying performance fatigue and perceived fatigue in response to motor and cognitive tasks as well as their interdependence, and (3) provide recommendations for future research on these interactions. We propose to define motor or cognitive task-induced state fatigue as a psychophysiological condition characterized by a decrease in motor or cognitive performance (i.e., motor or cognitive performance fatigue, respectively) and/or an increased perception of fatigue (i.e., perceived motor or cognitive fatigue). These dimensions are interdependent, hinge on different determinants, and depend on body homeostasis (e.g., wakefulness, core temperature) as well as several modulating factors (e.g., age, sex, diseases, characteristics of the motor or cognitive task). Consequently, there is no single factor primarily determining performance fatigue and perceived fatigue in response to motor or cognitive tasks. Instead, the relative weight of each determinant and their interaction are modulated by several factors.

What Modifies the Effect of an Exercise Treatment for Chronic Low Back Pain? A Meta-epidemiologic Regression Analysis of Risk of Bias and Comparative Effectiveness.

OBJECTIVE: To investigate how risk of bias and intervention type modify effect sizes of exercise interventions that are intended to reduce chronic low back pain intensity. DESIGN: Systematic review with meta-epidemiologic regression analysis. LITERATURE SEARCH: PubMed, CENTRAL, Embase, and CINAHL (until January 31, 2021). STUDY SELECTION CRITERIA: Systematic reviews with meta-analyses of randomized controlled exercise trials. DATA SYNTHESIS: The dependent variable was pain, calculated as standardized mean difference (SMD). Potential effect modifiers were risk of bias, exercise modes, study, and meta-analyses characteristics. Multilevel meta-regressions and inverse variance-weighted meta-regressions with random intercepts were modelled. RESULTS: Data from 26 systematic reviews (k = 349 effect sizes, n = 18,879 participants) were analysed. The overall mean effect was SMD: -0.35 (k = 349, [95% CI -0.02 to -0.7]). There was a clinically relevant effect overestimation in studies with a high risk of bias due to missing outcomes (each k = 197, Beta coefficient = -1.9 [95% CI -2.9 to -.9]) and low sample size (B = 0.01 [.001 to .01], [ie, one participant more leads to an SMD decrease of 0.01]). There was a clinically relevant underestimation of the effect when studies were at high risk of bias in allocation concealment (B = 1.3 [.5 to 2.1]) and outcome measurement (B = 1.3 [.44 to 2.0]). Motor control and stabilization training (B = -1.3 [-2.3 to -.37]) had the largest effects; stretching (B = 1.3 [-.03 to .5]) had the smallest effect. CONCLUSIONS: The effects of exercise trials at high risk of bias may be overestimated or underestimated. After accounting for risk of bias, motor control and stabilization exercises may represent the most effective exercise therapies for chronic low back pain. J Orthop Sports Phys Ther 2022;52(12):792-802. Epub: 12 August 2022. doi:10.2519/jospt.2022.11149.

Real-time metabolic monitoring under exhaustive exercise and evaluation of ventilatory threshold by breathomics: Independent validation of evidence and advances.

Breath analysis was coupled with ergo-spirometry for non-invasive profiling of physio-metabolic status under exhaustive exercise. Real-time mass-spectrometry based continuous analysis of exhaled metabolites along with breath-resolved spirometry and heart rate monitoring were executed while 14 healthy adults performed ergometric ramp exercise protocol until exhaustion. Arterial blood lactate level was analyzed at defined time points. Respiratory-cardiac parameters and exhalation of several blood-borne volatiles changed continuously with the course of exercise and increasing workloads. Exhaled volatiles mirrored ventilatory and/or hemodynamic effects and depended on the origin and/or physicochemical properties of the substances. At the maximum workload, endogenous isoprene, methanethiol, dimethylsulfide, acetaldehyde, butanal, butyric acid and acetone concentrations decreased significantly by 74, 25, 35, 46, 21, 2 and 2%, respectively. Observed trends in exogenous cyclohexadiene and acetonitrile mimicked isoprene profile due to their similar solubility and volatility. Assignment of anaerobic threshold was possible via breath acetone. Breathomics enabled instant profiling of physio-metabolic effects and anaerobic thresholds during exercise. Profiles of exhaled volatiles indicated effects from muscular vasoconstriction, compartmental distribution of perfusion, extra-alveolar gas-exchange and energy homeostasis. Sulfur containing compounds and butyric acid turned out to be interesting for investigations of combined diet and exercise programs. Reproducible metabolic breath patterns have enhanced scopes of breathomics in sports science/medicine.

Morality of the Heart: Heart Rate Variability and Moral Rule Adherence in Men.

Moral rules are a cornerstone of many societies. Most moral rules are concerned with the welfare of other individuals, reflecting individuals' innate aversion against harming other individuals. Harming others is associated with aversive experiences, implying that individuals who are sensitive to the aversiveness of these experiences are more likely to follow moral rules than individuals who are insensitive to the aversiveness of these experiences. Individuals' sensitivity for aversive experiences depends on individuals' ability to integrate the underlying neural and physiological processes: Individuals who are more efficient in integrating these processes are more sensitive to the aversiveness that is associated with moral rule violations than individuals who are less efficient in integrating these processes. Individuals who differ in their ability to integrate these processes may, thus, also differ in their inclination to follow moral rules. We tested this assumption in a sample of healthy individuals (67 males) who completed measures of moral rule adherence and integration abilities. Moral rule adherence was assessed with self-report measure and integration abilities were assessed with a resting state measure of heart rate variability (HRV), which reflects prefrontal-(para-)limbic engagement during the integration of physical and neural processes. We found a positive association between individuals' HRV and individuals' moral rule adherence, implying that individuals with efficient integration abilities were more inclined to follow moral rules than individuals with inefficient integration abilities. Our findings support the assumption that individuals with different integration abilities also differ in moral rule adherence, presumably because of differences in aversiveness sensitivity.

Oxyhemoglobin Concentration and Oxygen Uptake Signal During Recovery From Exhaustive Exercise in Healthy Subjects-Relationship With Aerobic Capacity.

This proof of concept study is dedicated to the quantification of the short-term recovery phase of the muscle oxygenation and whole-body oxygen uptake kinetics following an exhaustive cycling protocol. Data of 15 healthy young participants (age 26.1 ± 2.8 years, peak oxygen uptake 54.1 ± 5.1 mL∗min-1∗kg-1) were recorded during 5 min cool down-cycling with a power output of 50 W on an electro-magnetically braked cycle ergometer. The oxygen uptake (VO2) signal during recovery was modeled by exponential function. Using the model parameters, the time (T1/2) needed to return VO2 to 50% of VO2 peak was determined. The Hill's model was used to analyze the kinetics of oxyhemoglobin concentration (Sm, %), non-invasively recorded by near-infrared spectroscopy (NIRS) over the M. vastus lateralis. Analysis of the Pearson correlation results in statistically significant negative relationships between T1/2 and relative VO2 peak (r = -0.7). Relevant significant correlations were determined between constant defining the slope of VO2 decrease (parameter B) and the duration of the anaerobic phase (r = -0.59), as well as between Hill's coefficient and average median Smmax for the final 2 min of recovery. The high correlation between traditional variables commonly used to represent the cardio-metabolic capacity and the parameters of fits from exponential and Hill models attests the validity of our approach. Thus, proposed descriptors, derived from non-invasive NIRS monitoring during recovery, seem to reflect aerobic capacity. However, the practical usefulness of such modeling for clinical or other vulnerable populations has to be explored in studies using alternative testing protocols.

Individual performance progression of German elite female and male middle-distance runners.

Current standards for talent identification often base on age-related cross-sectional or mixed data analyses. Longitudinal studies of elite runners from their very early to their late career are still rare, despite their need for valid talent identification and prognoses. Thus, we analysed individual performance trajectories of German international level middle-distance runners (30 females, 41 males) from an age of 14 until their top performance. Quadratic equations best fitted the individual performances from 14 years to late career in relation to the world record time. The individual trajectories were further used to construct a global performance progression model, providing annual performance estimates (mean and standard deviation of 800, 1000 and 1500 m race times in relation to the current world record time) of later top runners from early to late career. Our analysis implies that, on average, females started from a higher performance level at young age. In contrast, average performance progression of the males was higher until the age of 17 years. Performance peaked at an age of 24.0 ± 3.0 and 23.3 ± 2.6 years for the female and male runners, respectively. The provided average annual performance progressions, as well as their ranges, may help coaches and sport federations in their decision making on age-related performance criteria for talent identification in middle-distance running.

Sex-Specific Relationships Between Interoceptive Accuracy and Emotion Regulation.

Over the last years, there has been a resurge in the interest to study the relationship between interoception and emotion. By now, it is well established that interoception contributes to the experience of emotions. However, it may also be possible that interoception contributes to the regulation of emotions. To test this possibility, we studied the relationship between interoception and emotion regulation in a sample of healthy individuals (n = 84). We used a similar heartbeat detection task and a similar self-report questionnaire for the assessment of interoceptive accuracy and emotion regulation as in previous studies. In contrast to previous studies, we differentiated between male and female individuals in our analyses and controlled our analyses for individual characteristics that may affect the relationship between interoceptive accuracy and emotion regulation. We found sex-differences in interoceptive accuracy and emotion regulation that amounted to a sex-specific relationship between interoceptive accuracy and emotion regulation: Whereas interoceptive accuracy was related to reappraisal but not to suppression in male individuals, interoceptive accuracy was unrelated to reappraisal and suppression in female individuals. These findings indicate that the relationship between interoception and emotion regulation is far more complex than has been suggested by previous findings. However, these findings nonetheless support the view that interoception is essential for both, the regulation and experience of emotions.

Heart Rate Variability Modulates Interoceptive Accuracy.

Our emotional experiences depend on our interoceptive ability to perceive and interpret changes in our autonomous nervous system. An inaccurate perception and interpretation of autonomic changes impairs our ability to understand and regulate our emotional reactions. Impairments in emotion understanding and emotion regulation increase our risk for mental disorders, indicating that interoceptive deficits play an important role in the etiology and pathogenesis of mental disorders. We, thus, need measures to identify those of us whose interoceptive deficits impair their emotion understanding and emotion regulation. Here, we used cardiac measures to investigate how our ability to engage prefrontal and (para-)limbic brain region regions affects our ability to perceive and interpret cardiac changes. We administered a heartbeat detection task to a sample of healthy individuals (n = 113) whose prefrontal-(para-) limbic engagement had been determined on basis of a heart rate variability recording. We found a positive association between heartbeat detection and heart rate variability, implying that individuals with higher heart rate variability were more accurate in heartbeat detection than individuals with lower heart rate variability. These findings suggest that our interoceptive accuracy depends on our prefrontal-(para-)limbic engagement during the perception and interpretation of cardiac changes. Our findings also show that cardiac measures may be useful to investigate the association between interoceptive accuracy and prefrontal-(para-)limbic engagement in a time- and cost-efficient manner.

Interoceptive accuracy is associated with emotional contagion in a valence- and sex-dependent manner.

Over the last years, the neurobiological mechanisms of empathy have been extensively investigated. Recent investigations suggest that interoceptive processes, in particular, those that are related to the experience and perception of cardiac changes, are relevant for affect sharing, mentalizing and self-other distinction. To further investigate the association between interoception and affect-sharing, we measured emotional contagion and interoceptive accuracy in a sample of healthy participants (n = 84). Emotional contagion was assessed with an established self-report questionnaire and interoceptive accuracy was assessed with a validated heartbeat detection task. Across a series of complementary analyses, we found a sex- and valence-dependent association between interoception and affection sharing: Among female but not male participants, interoceptive accuracy was positively associated with emotional contagion for negative but not positive states of others. We provide an evolutionary-based explanation for these findings, which are consistent with previous findings showing positive associations between interoceptive accuracy, mentalizing and self-other distinction.

Intrarater Reliability of Muscle Strength and Hamstring to Quadriceps Strength Imbalance Ratios During Concentric, Isometric, and Eccentric Maximal Voluntary Contractions Using the Isoforce Dynamometer.

OBJECTIVE: To determine intrasession and intersession reliability of strength measurements and hamstrings to quadriceps strength imbalance ratios (H/Q ratios) using the new isoforce dynamometer. DESIGN: Repeated measures. SETTING: Exercise science laboratory. PARTICIPANTS: Thirty healthy subjects (15 females, 15 males, 27.8 years). MAIN OUTCOME MEASURES: Coefficient of variation (CV) and intraclass correlation coefficients (ICC) were calculated for (1) strength parameters, that is peak torque, mean work, and mean power for concentric and eccentric maximal voluntary contractions; isometric maximal voluntary torque (IMVT); rate of torque development (RTD), and (2) H/Q ratios, that is conventional concentric, eccentric, and isometric H/Q ratios (Hcon/Qcon at 60 deg/s, 120 deg/s, and 180 deg/s, Hecc/Qecc at -60 deg/s and Hiso/Qiso) and functional eccentric antagonist to concentric agonist H/Q ratios (Hecc/Qcon and Hcon/Qecc). High reliability: CV <10%, ICC >0.90; moderate reliability: CV between 10% and 20%, ICC between 0.80 and 0.90; low reliability: CV >20%, ICC <0.80. RESULTS: (1) Strength parameters: (a) high intrasession reliability for concentric, eccentric, and isometric measurements, (b) moderate-to-high intersession reliability for concentric and eccentric measurements and IMVT, and (c) moderate-to-high intrasession reliability but low intersession reliability for RTD. (2) H/Q ratios: (a) moderate-to-high intrasession reliability for conventional ratios, (b) high intrasession reliability for functional ratios, (c) higher intersession reliability for Hcon/Qcon and Hiso/Qiso (moderate to high) than Hecc/Qecc (low to moderate), and (d) higher intersession reliability for conventional H/Q ratios (low to high) than functional H/Q ratios (low to moderate). CONCLUSIONS: The results have confirmed the reliability of strength parameters and the most frequently used H/Q ratios.

It's Harder to Push, When I Have to Push Hard-Physical Exertion and Fatigue Changes Reasoning and Decision-Making on Hypothetical Moral Dilemmas in Males.

Despite the prevalence of physical exertion and fatigue during military, firefighting and disaster medicine operations, sports or even daily life, their acute effects on moral reasoning and moral decision-making have never been systematically investigated. To test the effects of physical exertion on moral reasoning and moral decision-making, we administered a moral dilemma task to 32 male participants during a moderate or high intensity cycling intervention. Participants in the high intensity cycling group tended to show more non-utilitarian reasoning and more non-utilitarian decision-making on impersonal but not on personal dilemmas than participants in the moderate intensity cycling group. Exercise-induced exertion and fatigue, thus, shifted moral reasoning and moral decision-making in a non-utilitarian rather than utilitarian direction, presumably due to an exercise-induced limitation of prefrontally mediated executive resources that are more relevant for utilitarian than non-utilitarian reasoning and decision-making.

Relationship Between Morning Heart Rate Variability and Creatine Kinase Response During Intensified Training in Recreational Endurance Athletes.

Specific physiological responses and their relationship were analyzed in 12 recreational endurance athletes (43.8 ± 7.9 years) during a period of intensified cycling training. Heart rate (HR), HR variability (HRV), serum creatine kinase (S-CK) and haematocrit (Hct) were measured in the mornings before (PRE) and following three consecutive days of intensified training (POST 1-3). Morning HR increased during this period (PRE: 52.2 ± 6.7 bpm, POST 1: 58.8 ± 7.0 bpm, POST 2: 58.5 ± 8.1 bpm, POST 3: 57.9 ± 7.2 bpm; F(3,33) = 11.182, p < 0.001, ηp 2 = 0.554). Parasympathetic HRV indices decreased from PRE to POST (F(3,33) ≥ 11.588, p < 0.001, ηp 2 ≥ 0.563), no effect was found for sympathetically modulated HRV (F(3,33) = 2.287, p = 0.101, ηp 2 = 0.203). Hct decreased (PRE: 49.9 ± 4.0%, POST 1: 46.5 ± 5.1%, POST 2: 45.5 ± 3.8%, POST 3: 43.2 ± 3.4%; F(3,33) = 11.909, p < 0.001, ηp 2 = 0.520) and S-CK increased during the training period (PRE: 90.0 ± 32.1 U/L, POST 1: 334.7 ± 487.6 U/L, POST 2: 260.1 ± 303.4 U/L, POST 3: 225.1 ± 258.8 U/L; F(3,33) = 3.996, p = 0.017, ηp 2 = 0.285). S-CK release was associated with HR (r = 0.453, p = 0.002, n = 44), RMSSD (r = -0.494, p = 0.001, n = 44) and HF-Power (r = -0.490, p = 0.001, n = 44). A period of intensified training was associated with haemodilution, parasympathetic withdrawal and S-CK-increase. Cardiac autonomic control at morning rest correlated with the S-CK-release; and thus, may serve as a practical mean to complementary monitor and prescribe training load in this population.

Heart rate variability is associated with social value orientation in males but not females.

Phylogenetic and neurobiological theories suggest that inter-individual differences in high frequency heart rate variability (HF-HRV) are associated with inter-individual differences in social behavior and social cognition. To test these theories, we investigated whether individuals with high and low HF-HRV would show different preferences for cooperative behavior in social contexts. We recorded resting state HF-HRV in 84 healthy individuals before they completed the Social Value Orientation task, a well-established measure of cooperative preferences. HF-HRV was derived from short-term (300 s) and ultra-short-term (60 s, 120 s) recordings of participants' heart rate to determine the robustness of possible findings. Irrespective of recording length, we found a sex-dependent association between inter-individual differences in HF-HRV and inter-individual differences in social value orientation: The preference for cooperation was more pronounced among individuals with high as compared low HF-HRV, albeit only in male and not in female participants. These findings suggest that males with high HF-HRV are more inclined to engage in cooperative behavior than males with low HF-HRV.

Inter-individual Differences in Heart Rate Variability Are Associated with Inter-individual Differences in Empathy and Alexithymia.

In the present study, we investigated whether inter-individual differences in vagally mediated heart rate variability (vmHRV) would be associated with inter-individual differences in empathy and alexithymia. To this end, we determined resting state HF-HRV in 90 individuals that also completed questionnaires assessing inter-individual differences in empathy and alexithymia. Our categorical and dimensional analyses revealed that inter-individual differences in HF-HRV were differently associated with inter-individual differences in empathy and alexithymia. We found that individuals with high HF-HRV reported more empathy and less alexithymia than individuals with low HF-HRV. Moreover, we even found that an increase in HF-HRV was associated with an increase in empathy and a decrease in alexithymia across all participants. Taken together, these findings indicate that individuals with high HF-HRV are more empathetic and less alexithymic than individuals with low HF-HRV. These differences in empathy and alexithymia may explain why individuals with high HF-HRV are more successful in sharing and understanding the mental and emotional states of others than individuals with low HF-HRV.

Heart rate variability is associated with psychosocial stress in distinct social domains.

OBJECTIVE: Psychosocial stress is associated with substantial morbidity and mortality. Accordingly, there is a growing interest in biomarkers that indicate whether individuals show adaptive (i.e., stress-buffering and health-promoting) or maladaptive (i.e., stress-escalating and health-impairing) stress reactions in social contexts. As heart rate variability (HRV) has been suggested to be a biomarker of adaptive behavior during social encounters, it may be possible that inter-individual differences in HRV are associated with inter-individual differences regarding stress in distinct social domains. METHODS: To test this hypothesis, resting state HRV and psychosocial stress was assessed in 83 healthy community-dwelling individuals (age: 18-35years). HRV was derived from heart rate recordings during spontaneous and instructed breathing to assess the robustness of possible associations between inter-individual differences in HRV and inter-individual differences in psychosocial stress. Psychosocial stress was determined with a self-report questionnaire assessing stress in distinct social domains. RESULTS: A series of categorical and dimensional analyses revealed an association between inter-individual differences in HRV and inter-individual differences in psychosocial stress: Individuals with high HRV reported less stress in social life, but not in family life, work life or everyday life, than individuals with low HRV. CONCLUSIONS: On basis of these findings, it may be assumed that individuals with high HRV experience less psychosocial stress than individuals with low HRV. Although such an assumption needs to be corroborated by further findings, it seems to be consistent with previous findings showing that individuals with high HRV suffer less from stress and stress-related disorders than individuals with low HRV.

Mental Fatigue Increases Gait Variability During Dual-task Walking in Old Adults.

Background: Mental fatigue is a psychobiological state induced by sustained periods of demanding cognitive activity and is characterized by feelings of tiredness which are common in everyday life. Recently, it has been hypothesized that mental fatigue might have an impact on gait performance in old adults. Therefore, the effect of mental fatigue on gait performance under single- and dual-task conditions was investigated in young and old participants. Methods: Spatio-temporal gait parameters of 16 young and 16 old healthy participants were measured using a photoelectric system during single- and dual-task walking before and after a randomly assigned mental fatigue (performing a stop-signal task for 90 minutes) and control intervention (watching a video for 90 minutes), respectively. Changes in subjective fatigue, wakefulness, mood, arousal, and psychophysiological workload (heart rate variability indices) were assessed. Results: Psychometric measures indicated increased subjective fatigue and arousal as well as decreased mood and wakefulness after the mental fatigue task. Heart rate variability indices revealed a higher psychophysiological workload during the mental fatigue intervention in old compared to young participants. Gait measures (coefficient of variation of speed, stride length, and stance time) revealed impaired dual-task walking performance following the mental fatigue intervention only in old participants. Conclusion: Data indicate that mental fatigue, induced by sustained cognitive activity, can impair gait performance during dual-task walking in old adults. The susceptibility to mental fatigue could be a new intrinsic risk factor for falls in older people and should be taken into account when dual-task gait analyses are performed.

Sex-Specific Associations Between Inter-Individual Differences in Heart Rate Variability and Inter-Individual Differences in Emotion Regulation.

Neurobiological theories suggest that inter-individual differences in vagally mediated heart rate variability (vmHRV) have the potential to serve as a biomarker for inter-individual differences in emotion regulation that are due to inter-individual differences regarding the engagement of prefrontal and (para-)limbic brain regions during emotion processing. To test these theories, we investigated whether inter-individual differences in vmHRV would be associated with inter-individual differences in emotion regulation. We determined resting state vmHRV in a sample of 176 individuals that had also completed a short self-report measure of reappraisal and suppression use. Resting state vmHRV was derived from short-term (300 s) and ultra-short-term (120 s, 60 s) recordings of participants' heart rate to determine the robustness of possible findings. Irrespective of recording length, we found that an increase in resting state vmHRV was associated with an increase in self-reported reappraisal but not suppression use. However, this association was only evident among male but not female participants, indicating a sex-specific association between inter-individual differences in resting state vmHRV and inter-individual differences in self-reported emotion regulation. These findings, which are consistent with previous ones, support theoretical claims that inter-individual differences in vmHRV serve as a biomarker for inter-individual differences in emotion regulation. Combing (ultra-)short-term measures of resting state vmHRV with short self-report measures of emotion regulation may, thus, be useful for researchers who have to investigate the neurobiological mechanisms of emotion regulation in a time- and resource-efficient manner.

Cycling before and after Exhaustion Differently Affects Cardiac Autonomic Control during Heart Rate Matched Exercise.

During cycling before (PRE) and after exhaustion (POST) different modes of autonomic cardiac control might occur due to different interoceptive input and altered influences from higher brain centers. We hypothesized that heart rate variability (HRV) is significantly affected by an interaction of the experimental period (PRE vs. POST) and exercise intensity (HIGH vs. LOW; HIGH = HR > HR at the lactate threshold (HRLT), LOW = HR ≤ HRLT) despite identical average HR. Methods: Fifty healthy volunteers completed an incremental cycling test until exhaustion. Workload started with 30 W at a constant pedaling rate (60 revolutions · min-1) and was gradually increased by 30 W · 5 min-1. Five adjacent 60 s inter-beat (R-R) interval segments from the immediate recovery period (POST 1-5 at 30 W and 60 rpm) were each matched with their HR-corresponding 60 s-segments during the cycle test (PRE 1-5). An analysis of covariance was carried out with one repeated-measures factor (PRE vs. POST exhaustion), one between-subject factor (HIGH vs. LOW intensity) and respiration rate as covariate to test for significant effects (p < 0.050) on the natural log-transformed root mean square of successive differences between adjacent R-R intervals (lnRMSSD60s). Results: LnRMSSD60s was significantly affected by the interaction of experimental period × intensity [F(1, 242) = 30.233, p < 0.001, η p2 = 0.111]. LnRMSSD60s was higher during PRE compared to POST at LOW intensity (1.6 ± 0.6 vs. 1.4 ± 0.6 ms; p < 0.001). In contrast, at HIGH intensity lnRMSSD60s was lower during PRE compared to POST (1.0 ± 0.4 vs. 1.2 ± 0.4 ms; p < 0.001). Conclusion: Identical net HR during cycling can result from distinct autonomic modulation patterns. Results suggest a pronounced sympathetic-parasympathetic coactivation immediately after the cessation of peak workload compared to HR-matched cycling before exhaustion at HIGH intensity. On the opposite, at LOW intensity cycling, a stronger coactivational cardiac autonomic modulation pattern occurs during PRE-exhaustion if compared to POST-exhaustion cycling. The different autonomic modes during these phases might be the result of different afferent and/or central inputs to the cardiovascular control centers in the brainstem.

Neuromuscular function of the quadriceps muscle during isometric maximal, submaximal and submaximal fatiguing voluntary contractions in knee osteoarthrosis patients.

INTRODUCTION: Knee osteoarthrosis (KOA) is commonly associated with a dysfunction of the quadriceps muscle which contributes to alterations in motor performance. The underlying neuromuscular mechanisms of muscle dysfunction are not fully understood. The main objective of this study was to analyze how KOA affects neuromuscular function of the quadriceps muscle during different contraction intensities. MATERIALS AND METHODS: The following parameters were assessed in 20 patients and 20 healthy controls: (i) joint position sense, i.e. position control (mean absolute error, MAE) at 30° and 50° of knee flexion, (ii) simple reaction time task performance, (iii) isometric maximal voluntary torque (IMVT) and root mean square of the EMG signal (RMS-EMG), (iv) torque control, i.e. accuracy (MAE), absolute fluctuation (standard deviation, SD), relative fluctuation (coefficient of variation, CV) and periodicity (mean frequency, MNF) of the torque signal at 20%, 40% and 60% IMVT, (v) EMG-torque relationship at 20%, 40% and 60% IMVT and (vi) performance fatigability, i.e. time to task failure (TTF) at 40% IMVT. RESULTS: Compared to the control group, the KOA group displayed: (i) significantly higher MAE of the angle signal at 30° (99.3%; P = 0.027) and 50° (147.9%; P < 0.001), (ii) no significant differences in reaction time, (iii) significantly lower IMVT (-41.6%; P = 0.001) and tendentially lower RMS-EMG of the rectus femoris (-33.7%; P = 0.054), (iv) tendentially higher MAE of the torque signal at 20% IMVT (65.9%; P = 0.068), significantly lower SD of the torque signal at all three torque levels and greater MNF at 60% IMVT (44.8%; P = 0.018), (v) significantly increased RMS-EMG of the vastus lateralis at 20% (70.8%; P = 0.003) and 40% IMVT (33.3%; P = 0.034), significantly lower RMS-EMG of the biceps femoris at 20% (-63.6%; P = 0.044) and 40% IMVT (-41.3%; P = 0.028) and tendentially lower at 60% IMVT (-24.3%; P = 0.075) and (vi) significantly shorter TTF (-51.1%; P = 0.049). CONCLUSION: KOA is not only associated with a deterioration of IMVT and neuromuscular activation, but also with an impaired position and torque control at submaximal torque levels, an altered EMG-torque relationship and a higher performance fatigability of the quadriceps muscle. It is recommended that the rehabilitation includes strengthening and fatiguing exercises at maximal and submaximal force levels.