Cognitive control processes associated with successful gait performance in dual-task walking in healthy young adults.

Growing evidence suggests that the reliance on cognitive control processes during normal walking increases as the locomotor task gets more complex and challenging. The aims of the present study were to explore the (negative) effects of smartphone gaming on gait performance in healthy young adults, and to identify cognitive resources that might help to maintain high gait performance during dual-task walking. Gait speed and gait variability during walking at a self-selected comfortable speed were assessed in 40 healthy, young adults, and compared between single-task and dual-task walking (i.e., concurrent smartphone gaming) in undisturbed, simple and more challenging walking environments (i.e., stepping over an obstacle while walking). Based on single-task performance, dual-tasking costs were computed and linked to higher-level cognitive control processes, which were assessed for each individual. Cognitive function testing encompassed tests on the mental representation of the gait, working memory capacity, inhibitory control and cognitive flexibility. Our data revealed that gaming on a smartphone while walking strongly affected participants' gait performance (i.e., up to 26.8% lower gait speed and 60.2% higher gait variability), and decrements in gait performance were related to higher cognitive control processes. Cognitive resources that were associated with performance decrements in dual-task walking include response inhibition, cognitive flexibility, working memory, and a well-structured mental representation of the gait. From that, it appears that even in healthy young adults better cognitive resources may help to maintain high gait performance in situations, in which we have to deal with dual- or multi-task demands (e.g., using a smartphone) while walking.

The mental representation of the human gait in hip osteoarthrosis and total hip arthroplasty patients: A clinical cross-sectional study.

OBJECTIVE:: To explore differences in gait-specific long-term memory structures and actual gait performance between patients with hip osteoarthrosis, patients seen six months after total hip arthroplasty and healthy controls to gain insights into the role of the gait-specific mental representation for rehabilitation. DESIGN:: Cross-sectional study. SUBJECTS:: Twenty hip osteoarthrosis patients, 20 patients seen six months after total hip arthroplasty and 20 healthy controls. METHODS:: Spatio-temporal (gait speed, step length) and temporophasic (stance time, swing time, single support time, total double support time) gait parameters, and gait variability were measured with an electronic walkway (OptoGait). The gait-specific mental representation was assessed using the structural dimensional analysis of mental representations (SDA-M). RESULTS:: Hip osteoarthrosis patients showed significantly longer stance and total double support times, shorter swing and single support times, and a decreased gait speed as compared with healthy controls (all P < 0.01). The differences in double support times were still evident in patients seen six months after total hip arthroplasty ( P < 0.01). The gait-specific mental representation differed between hip osteoarthrosis patients and healthy controls with regard to mid-stance and mid-swing phases; the mid-stance phase was still affected six months after total hip arthroplasty (both P < 0.05). CONCLUSION:: Our data indicated that actual gait performance and gait-specific long-term memory structures differ between hip osteoarthrosis patients and healthy controls. Important, some of these disease-related changes were still evident in patients seen six months after total hip arthroplasty.

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.

The mental representation of the human gait in patients with severe knee osteoarthrosis: a clinical study to aid understanding of impairment and disability.

OBJECTIVE: Objectives were (1) to explore differences in gait-specific long-term memory structures and gait performance between knee osteoarthrosis patients and healthy subjects and (2) to identify the extent to which the gait-specific mental representation is associated with gait performance. DESIGN: Cross-sectional study. SUBJECTS: In total, 18 knee osteoarthrosis patients and 18 control subjects. METHODS: Spatio-temporal (gait speed, step length) and temporophasic (stance time, swing time, single support time, total double support time) gait parameters and gait variability were measured with an electronic walkway (OptoGait). The mental representation was assessed using the structural dimensional analysis of mental representations (SDA-M). RESULTS: (1) Patients showed significantly longer stance times ( P < 0.002) and total double support times, shorter swing times and single support times, a decreased gait speed ( P-values < 0.001) and structural differences in the gait-specific mental representation as compared with the healthy controls. (2) Correlation analyses revealed the mental representation of the human gait to be associated with actual gait performance in osteoarthrosis patients. Double support times were positively associated with the structural quality of the mental representation and step length variability was positively associated with the number of sequencing errors in the representation. CONCLUSION: The gait-specific mental representation and actual gait performance differ between patients with severe knee osteoarthrosis and healthy controls, and both are linked to one another. This finding suggests that musculoskeletal disorders can lead to changes in the mental representation of the gait, and as such the SDA-M could provide useful information to improve the rehabilitation following osteoarthrosis.

Intersession reliability of the interpolated twitch technique applied during isometric, concentric, and eccentric actions of the human knee extensor muscles.

INTRODUCTION: Although it has been shown that voluntary activation (%VA) of the knee extensors during isometric contractions can be reliably assessed with the interpolated twitch technique, little is known about the reliability of %VA during concentric and eccentric muscle actions. Therefore, relative and absolute intersession reliability of quadriceps muscle's %VA during different contraction modes was determined. METHODS: After a familiarization session, 21 participants (17 males, 25 ± 2 yrs) completed two testing sessions. Paired supramaximal electrical stimuli were administered to the femoral nerve during isometric, concentric, eccentric MVCs, and at rest to assess %VA (stimuli were applied at 70° knee flexion). RESULTS AND DISCUSSION: Data indicate that %VA of the knee extensors can be reliably measured during isometric [intraclass correlation coefficient (ICC) = 0.89, coefficient of variation (CV) = 4.1%], concentric (ICC = 0.87, CV = 6.6%), and eccentric muscle actions (ICC = 0.86, CV = 7.0%). Muscle Nerve 56: 324-327, 2017.

The Relationship between Lean Mass and Contractile Properties of the Quadriceps in Elderly and Young Adults.

BACKGROUND: Aging is associated with a loss of muscle mass (sarcopenia) and function. The twitch torque evoked by supramaximal electrical stimulation of peripheral nerves has been frequently used to analyse age-related modulations at the skeletal muscle level, such as changes in muscle mass. However, only one study has investigated the association between twitch contractile properties and skeletal muscle mass. A significant positive correlation between cross-sectional area and twitch parameters was found for the plantar flexors in young adults when using supramaximal doublet stimulation. It remains unclear whether this relationship exists for the quadriceps in elderly and young subjects when using single and doublet stimulation. OBJECTIVE: The aim of the present study was to investigate the relationship between the lean mass of the thigh and evoked twitch properties of the quadriceps using single and doublet stimulation in two age groups. METHODS: Fifteen young (aged 25.3 ± 3.6 years) and 15 elderly (aged 69.6 ± 3.1 years) subjects were recruited to participate in this study. The lean mass of the thigh was measured by dual-energy X-ray absorptiometry. Supramaximal single and doublet electrical stimulation was used to assess the contractile properties of the quadriceps. RESULTS: We observed no significant associations between lean mass and contractile properties when using single stimulation. Significant positive correlations were shown between lean mass and peak twitch torque evoked by doublet stimulation in young (r = 0.56; p = 0.030) and elderly (r = 0.54; p = 0.040) subjects. The analysis of twitch time and slope parameters demonstrated no significant correlations with lean mass. CONCLUSION: The peak twitch torque evoked by doublet electrical stimulation seems to be an appropriate measure to assess modulations in muscle mass in elderly and young subjects. The use of supramaximal single stimulation and the analysis of time and slope parameters may not be recommended for estimating changes in muscle mass. Consequently, the occurrence of muscle mass loss with aging can be identified from the twitch torque signal induced by doublet stimulation, which is a simple and favorable way to estimate sarcopenia.

Alteration in neuromuscular function of the plantar flexors following caffeine ingestion.

The aim of this study was to compare the neuromuscular function of the plantar flexors following caffeine or placebo administration. Thirteen subjects (25 ± 3 years) ingested caffeine or placebo in a randomized, controlled, counterbalanced, double-blind crossover design. Neuromuscular tests were performed before and 1 h after caffeine or placebo intake. During neuromuscular testing, rate of torque development, isometric maximum voluntary torque, and neural drive to the muscles were measured. Triceps surae muscle activation was assessed by normalized root mean square of the EMG signal during the initial phase of contraction (0-100 ms, 100-200 ms) and maximal voluntary contraction (MVC). Furthermore, evoked spinal reflex responses of the soleus muscle (H-reflex evoked at rest and during MVC, V-wave) and peak twitch torques were evaluated. The isometric maximum voluntary torque and evoked potentials were not different. However, we found a significant difference between groups for rate of torque development in the time intervals 0-100 ms [41.1 N · m/s (95% CI: 8.3-73.9 N · m/s, P = 0.016)] and 100-200 ms [32.8 N · m/s (95% CI: 2.8-62.8 N · m/s, P = 0.034)]. These changes were accompanied by enhanced neural drive to the plantar flexors. Data suggest that caffeine solely increased explosive voluntary strength of the triceps surae because of enhanced neural activation at the onset of contraction whereas MVC strength was not affected.

Effect of balance training on neuromuscular function at rest and during isometric maximum voluntary contraction.

PURPOSE: This study was directed to investigate the neuromuscular function of the plantar flexors and tibialis anterior (TA) before and after 8 weeks of balance training. METHODS: Twenty-six young adult subjects were randomly assigned to an intervention group and a control group. During neuromuscular testing, rate of torque development (RTD), isometric maximum voluntary torque (iMVT) and muscle activation were measured. Triceps surae muscle activation and TA muscle co-activation were assessed by normalized root mean square of the EMG signal during the initial phase of contraction (0-100, 0-200 ms) and maximum voluntary contraction (MVC) of the plantar flexors. Furthermore, evoked spinal reflex responses of the soleus muscle (H-reflex evoked at rest and during MVC, V-wave), peak twitch torques induced by electrical stimulation at rest and balance performance were evaluated. RESULTS: We found a significant difference between groups in RTD of the plantar flexors during MVC in the time interval 0-100 ms [37.0 N m s(-1) (4.2-69.9 N m s(-1), P = 0.029)]. This change was accompanied by reduced antagonistic muscle co-activity. The normalized H-reflex of the soleus muscle at rest as well as the sway of the center of pressure during balance performance assessment were significantly lower for the intervention group compared with controls. The training intervention had no effect on iMVT, normalized muscle activity of the plantar flexors, normalized muscle activity of TA, normalized V-wave and normalized H-reflex evoked during MVC. CONCLUSION: Data suggest that balance training reduced antagonistic muscle co-activity at the onset of triceps surae contraction and, in turn, increased isometric explosive voluntary strength of the plantar flexors.

Accuracy of a custom physical activity and knee angle measurement sensor system for patients with neuromuscular disorders and gait abnormalities.

Long-term assessment of ambulatory behavior and joint motion are valuable tools for the evaluation of therapy effectiveness in patients with neuromuscular disorders and gait abnormalities. Even though there are several tools available to quantify ambulatory behavior in a home environment, reliable measurement of joint motion is still limited to laboratory tests. The aim of this study was to develop and evaluate a novel inertial sensor system for ambulatory behavior and joint motion measurement in the everyday environment. An algorithm for behavior classification, step detection, and knee angle calculation was developed. The validation protocol consisted of simulated daily activities in a laboratory environment. The tests were performed with ten healthy subjects and eleven patients with multiple sclerosis. Activity classification showed comparable performance to commercially available activPAL sensors. Step detection with our sensor system was more accurate. The calculated flexion-extension angle of the knee joint showed a root mean square error of less than 5° compared with results obtained using an electro-mechanical goniometer. This new system combines ambulatory behavior assessment and knee angle measurement for long-term measurement periods in a home environment. The wearable sensor system demonstrated high validity for behavior classification and knee joint angle measurement in a laboratory setting.

The effect of continuous passive motion and sling exercise training on clinical and functional outcomes following total knee arthroplasty: a randomized active-controlled clinical study.

BACKGROUND: The parallel-group randomized active-controlled clinical study was conducted to compare the effectiveness of two in-hospital range of motion (ROM) exercise programs following total knee arthroplasty (TKA). Continuous passive motion (CPM) is frequently used to increase ROM and improve postoperative recovery despite little conclusive scientific evidence. In contrast, a new active sling-based ROM therapy requires the activation of the knee joint muscles and dynamic joint stabilization. It was hypothesized that higher demands on muscle strength and muscle coordination during sling exercise training (ST) might be advantageous for early recovery following TKA. METHODS: A total of 125 patients undergoing primary TKA were assessed for eligibility. Thirty-eight patients were randomly assigned to receive ST or CPM (control intervention) during hospital stay. Patients were assessed before TKA for baseline measurement (pretest), 1 day before discharge (posttest) and 3 months after TKA (follow-up). The passive knee flexion range of motion (pFL) was the primary outcome measure. Secondary outcome measures included active knee flexion range of motion, active and passive knee extension ROM, static postural control, physical activity, pain, length of hospital stay as well as clinical, functional and quality-of-life outcomes (SF-36, HSS and WOMAC scores). Data were analyzed according to the intention-to-treat principle. Differences between the groups were tested for significance by the unpaired Student's t test or an analysis of covariance (ANCOVA) adjusted for baseline, weight, sex, age, pain and physical activity. RESULTS: A between-group difference could be determined at posttest. The pFL was significantly higher by 6.0° (95% CI 0.9 to 11.2°; P = 0.022) in the ST group. No difference between groups in pFL was documented at follow-up. Furthermore, no significant differences could be observed for any secondary outcome measure at posttest and follow-up. CONCLUSIONS: ST seems to have a clinically relevant beneficial short-term effect on pFL compared to CPM. The results support the implementation of ST in rehabilitation programs following TKA. LEVEL OF EVIDENCE: Therapy, level 2b.

Alexithymic But Not Autistic Traits Impair Prosocial Behavior.

Social impairments are a core feature of autism-spectrum disorders. However, there is a considerable variability in these impairments. Most autistic individuals show large impairments in social functioning but some autistic individuals show small impairments in social functioning. The variability of these impairments has been attributed to the presence or absence of alexithymia. To address this issue, we capitalized on the fact that alexithymic and autistic traits are broadly distributed in the population. This allowed us to investigate how alexithymic and autistic traits affect social functioning in healthy individuals. Healthy individuals showed impairments on a resource-allocation task that were due to alexithymic but not autistic traits. These findings suggest that alexithymic rather than autistic traits impair prosocial behavior across the autism-spectrum.

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.

Low-Load Unilateral and Bilateral Resistance Training to Restore Lower Limb Function in the Early Rehabilitation After Total Knee Arthroplasty: A Randomized Active-Controlled Clinical Trial.

Background: Continuous passive motion (CPM) is frequently used during rehabilitation following total knee arthroplasty (TKA). Low-load resistance training (LLRT) using continuous active motion (CAM) devices is a promising alternative. We investigated the effectiveness of CPM compared to LLRT using the affected leg (CAMuni) and both legs (CAMbi) in the early post-operative rehabilitation. HYPOTHESES: (I) LLRT (CAMuni and CAMbi) is superior to CPM, (II) additional training of the unaffected leg (CAMbi) is more effective than unilateral training (CAMuni). Materials and Methods: Eighty-five TKA patients were randomly assigned to three groups, respectively: (i) unilateral CPM of the operated leg; (ii) unilateral CAM of the operated leg (CAMuni); (iii) bilateral alternating CAM (CAMbi). Patients were assessed 1 day before TKA (pre-test), 1 day before discharge (post-test), and 3 months post-operatively (follow-up). PRIMARY OUTCOME: active knee flexion range of motion (ROMFlex). SECONDARY OUTCOMES: active knee extension ROM (ROMExt), swelling, pain, C-reactive protein, quality of life (Qol), physical activity, timed-up-and-go performance, stair-climbing performance, quadriceps muscle strength. Analyses of covariances were performed (modified intention-to-treat and per-protocol). Results: Hypothesis I: Primary outcome: CAMbi resulted in a higher ROMFlex of 9.0° (95%CI -18.03-0.04°, d = 0.76) and 6.3° (95%CI -14.31-0.99°, d = 0.61) compared to CPM at post-test and follow-up, respectively. SECONDARY OUTCOMES: At post-test, C-reactive protein was lower in both CAM groups compared with CPM. Knee pain was lower in CAMuni compared to CPM. Improved ROMExt, reduced swelling, better stair-climbing and timed-up-and-go performance were observed for CAMbi compared to CPM. At follow-up, both CAM groups reported higher Qol and CAMbi showed a better timed-up-and-go performance. Hypothesis II: Primary outcome: CAMbi resulted in a higher knee ROMFlex of 6.5° (95%CI -2.16-15.21°, d = 0.56) compared to CAMuni at post-test. SECONDARY OUTCOMES: At post-test, improved ROMExt, reduced swelling, and better timed-up-and-go performance were observed in CAMbi compared to CAMuni. Conclusions: Additional LLRT of the unaffected leg (CAMbi) seems to be more effective for recovery of function than training of the affected leg only (CAMuni), which may be mediated by positive transfer effects from the unaffected to the affected limb (cross education) and/or preserved neuromuscular function of the trained, unaffected leg. Trial Registration: ClinicalTrials.gov Identifier: NCT02062138.

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.

Reading the Mind in the Eyes of Children Test (RME-C-T): Development and Validation of a Complex Emotion Recognition Test.

Much research has been devoted to the development of emotion recognition tests that can be used to investigate how individuals identify and discriminate emotional expressions of other individuals. One of the most prominent emotion recognition tests is the Reading the Mind in the Eyes Test (RME-T). The original RME-T has been widely used to investigate how individuals recognize complex emotional expressions from the eye region of adult faces. However, the RME-T can only be used to investigate inter-individual differences in complex emotion recognition during the processing of adult faces. To extend its usefulness, we developed a modified version of the RME-T, the Reading the Mind in the Eyes of Children Test (RME-C-T). The RME-C-T can be used to investigate how individuals recognize complex emotional expressions from the eye region of child faces. However, the validity of the RME-C-T has not been evaluated yet. We, thus, administered the RME-C-T together with the RME-T to a sample of healthy adult participants (n = 119). The Interpersonal Reactivity Index (IRI) and the Toronto Alexithymia Scale (TAS) were also administered. Participants' RME-C-T performance correlated with participants' RME-T performance, implying that the RME-C-T measures similar emotion recognition abilities as the RME-T. Participants' RME-C-T performance also correlated with participants' IRI and TAS scores, indicating that these emotion recognition abilities are affected by empathetic and alexithymic traits. Moreover, participants' RME-C-T performance differed between participants with high and low TAS scores, suggesting that the RME-C-T is sensitive enough to detect impairments in these emotion recognition abilities. The RME-C-T, thus, turned out to be a valid measure of inter-individual differences in complex emotion recognition during the processing of child faces.

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.

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.

Measuring lower limb circumference and volume - introduction of a novel optical 3D volumetric measurement system.

This study comprised two experiments: (1) the reliability of a novel optical three-dimensional (3D) volumetric measurement system (BODYTRONIC® 600) for the assessment of lower limb circumference and volume; (2) the comparison of data obtained from BODYTRONIC® 600 with that provided by computed tomography (CT) for accuracy estimation. Reliability was assessed in 20 healthy subjects. Accuracy was determined by comparing the deviations in the surface topology of two 3D models obtained from BODYTRONIC® 600 and CT. Reliability was very high for leg circumference measures [coefficient of variations (CVs) range 0.3%-1.3%] and slightly lower for foot circumference (CVs around 2.0%). Reliability of leg volume was also found to be very high (CVs ≤ 2.5%). Differences in surface topology between BODYTRONIC® 600 and CT were primarily below 1 mm indicating high accuracy. The volumes of the foot were higher (range 0.9%-1.7%) and that of the leg, lower (range 1.0%-1.3%) compared to CT. The BODYTRONIC® 600 system provides fast, highly reliable and accurate measures of lower limb circumference and volume and can be considered as a valuable measurement tool for use in various research and clinical applications.

Neuromuscular Properties of the Human Wrist Flexors as a Function of the Wrist Joint Angle.

The joint angle dependence of voluntary activation and twitch properties has been investigated for several human skeletal muscles. However, although they play a key role for hand function and possess a unique neural control compared to muscles surrounding other joint complexes, little is known about the wrist flexors innervated by the median nerve. Therefore, isometric voluntary and electrically evoked contractions of the wrist flexors were analyzed at three wrist joint angles (extension: -30°, neutral: 0°, flexion: 30°) to quantify the joint angle dependence of (i) voluntary activation (assessed via peripheral nerve stimulation and electromyography [EMG]), (ii) unpotentiated twitch torques, and (iii) potentiated twitch torques. Maximum voluntary torque was lower in extension compared to neutral and flexion. Although voluntary activation was generally high, data indicate that voluntary activation of the wrist flexors innervated by the median nerve was lower and the antagonist·agonist-1 EMG ratio was higher with the wrist joint in flexion compared to extension. Peak twitch torque, rate of twitch torque development, and twitch half-relaxation time increased, whereas electromechanical delay decreased from flexion to extension for the unpotentiated twitch torques. Activity-induced potentiation partly abolished these differences and was higher in short than long wrist flexors. Different angle-dependent excitatory and inhibitory inputs to spinal and supraspinal centers might be responsible for the altered activation of the investigated wrist muscles. Potential mechanisms were discussed and might have operated conjointly to increase stiffness of the flexed wrist joint. Differences in twitch torque properties were probably related to angle-dependent alterations in series elastic properties, actin-myosin interaction, Ca2+ sensitivity, and phosphorylation of myosin regulatory light chains. The results of the present study provide valuable information about the contribution of neural and muscular properties to changes in strength capabilities of the wrist flexors at different wrist joint angles. These data could help to understand normal wrist function, which is a first step in determining mechanisms underlying musculoskeletal disorders and in giving recommendations for the restoration of musculoskeletal function after traumatic or overuse injuries.

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.