Search results for " variability"
showing 10 items of 853 documents
Quantifying Net Synergy/Redundancy of Spontaneous Variability Regulation via Predictability and Transfer Entropy Decomposition Frameworks.
2017
Objective: Indexes assessing the balance between redundancy and synergy were hypothesized to be helpful in characterizing cardiovascular control from spontaneous beat-to-beat variations of heart period (HP), systolic arterial pressure (SAP), and respiration (R). Methods: Net redundancy/synergy indexes were derived according to predictability and transfer entropy decomposition strategies via a multivariate linear regression approach. Indexes were tested in two protocols inducing modifications of the cardiovascular regulation via baroreflex loading/unloading (i.e., head-down tilt at −25° and graded head-up tilt at 15°, 30°, 45°, 60°, 75°, and 90°, respectively). The net redundancy/synergy of …
Spatial variability of muscle activity during human walking: The effects of different EMG normalization approaches
2015
Human leg muscles are often activated inhomogeneously, e.g. in standing. This may also occur in complex tasks like walking. Thus, bipolar surface electromyography (sEMG) may not accurately represent whole muscle activity. This study used 64-electrode high-density sEMG (HD-sEMG) to examine spatial variability of lateral gastrocnemius (LG) muscle activity during the stance phase of walking, maximal voluntary contractions (MVCs) and maximal M-waves, and determined the effects of different normalization approaches on spatial and inter-participant variability. Plantar flexion MVC, maximal electrically elicited M-waves and walking at self-selected speed were recorded in eight healthy males aged 2…
Pressure pain thresholds: Subject factors and the meaning of peak pressures.
2017
Background The assessment of pressure pain has become an integral part in pain research. The distribution of pressure under a plunger can be uneven. However, measurements based on conventional devices show the applied force or mean pressure, failing to take local pressure peaks into account. Our main question was whether peak pressures under the probe are responsible for pain onset. Methods A force-controlled algometer was fitted with a newly developed pressure-indicating film. Pressure pain thresholds (PPTs) of 100 healthy subjects (57 men, age 18-66 years) were assessed at 29 sites across the body. Each site was measured three times, nonconsecutively and presented in randomized order. For…
Categorizing the Role of Respiration in Cardiovascular and Cerebrovascular Variability Interactions
2022
Objective: Respiration disturbs cardiovascular and cerebrovascular controls but its role is not fully elucidated. Methods: Respiration can be classified as a confounder if its observation reduces the strength of the causal relationship from source to target. Respiration is a suppressor if the opposite situation holds. We prove that a confounding/suppression (C/S) test can be accomplished by evaluating the sign of net redundancy/synergy balance in the predictability framework based on multivariate autoregressive modelling. In addition, we suggest that, under the hypothesis of Gaussian processes, the C/S test can be given in the transfer entropy decomposition framework as well. Experimental p…
Inter-individual variability of protein patterns in saliva of healthy adults
2009
International audience; In order to document inter-individual variability in salivary protein patterns, unstimulated whole saliva was obtained from 12 subjects at 10 am and 3 pm of the same day. Saliva proteins were separated using two-dimensional gel electrophoresis, and semi-quantified using image analysis. One-way ANOVA was used to test the effects “time of sampling” and “subject”. Data were further explored by multivariate analyses (PCA, hierarchical clustering). Spots of interest were identified by mass spectrometry (MALDI-TOF MS/MS and nanoLC ESI-IT MS/MS). A dataset of 509 spots matched in all gels was obtained. There was no diurnal statistical effect on salivary patterns while inter…
Motor recruitment during action observation: Effect of interindividual differences in action strategy
2020
Abstract Visual processing of other’s actions is supported by sensorimotor brain activations. Access to sensorimotor representations may, in principle, provide the top-down signal required to bias search and selection of critical visual features. For this to happen, it is necessary that a stable one-to-one mapping exists between observed kinematics and underlying motor commands. However, due to the inherent redundancy of the human musculoskeletal system, this is hardly the case for multijoint actions where everyone has his own moving style (individual motor signature—IMS). Here, we investigated the influence of subject’s IMS on subjects’ motor excitability during the observation of an actor…
Heart rate variability related to effort at work
2011
Changes in autonomic nervous system function have been related to work stress induced increases in cardiovascular morbidity and mortality. Our purpose was to examine whether various heart rate variability (HRV) measures and new HRV-based relaxation measures are related to self-reported chronic work stress and daily emotions. The relaxation measures are based on neural network modelling of individual baseline heart rate and HRV information. Nineteen healthy hospital workers were studied during two work days during the same work period. Daytime, work time and night time heart rate, as well as physical activity were recorded. An effort-reward imbalance (ERI) questionnaire was used to assess ch…
Physiological responses and parasympathetic reactivation in rescue interventions: The effect of the breathing apparatus.
2018
This study aimed to assess the effect of wearing a breathing apparatus during a simulated rescue intervention on psychophysiological responses and parasympathetic reactivation of firefighters. Thirty-four firefighters participated in this study which consisted of four experimental sessions conducted randomly: a maximal fitness test and three rescue interventions performed (a) with personal protective clothing (PPC); (b) with PPC and the full self-contained breathing apparatus (SCBA), including cylinder, full-face piece, and breathing regulator; and (c) with PPC and only the cylinder of the self-contained breathing apparatus (SCBAc). Physiological (heart rate [HR], breathing frequency [BF]) …
Daily eudaimonic well-being as a predictor of daily performance: A dynamic lens.
2019
Sustaining employees' well-being and high performance at work is a challenge for organizations in today's highly competitive environment. This study examines the dynamic reciprocal relationship between the variability in office workers' eudaimonic well-being (i.e., activity worthwhileness) and their extra-role performance. Eighty-three white-collar employees filled in a diary questionnaire twice a day, once in the morning and once in the afternoon, on four consecutive working days. The results show that eudaimonic well-being displays clear variability in a short time frame. In addition, Bayesian Multilevel Structural Equation Models (MSEMs) reveal a significant positive relationship between…
Autonomic markers associated with generalized social phobia symptoms: heart rate variability and salivary alpha-amylase.
2016
The study of autonomic nervous system changes associated with generalized social phobia (GSP) disorder has increased in recent years, showing contradictory results. The present study aimed to evaluate how young people with GSP reacted before, during, and after exposure to the Trier Stress Social Test (TSST), focusing on their autonomic changes (heart rate variability (HRV) and salivary alpha-amylase (sAA)) compared to a control group (non-GSP). Some psychological variables were also considered. Sex was specifically studied as a possible modulator of autonomic fluctuations and psychological state. Eighty young people were randomly distributed into two counterbalanced situations: stress condi…