Functional indices of the human state and work capacity under monotonous conditions

The operator's letter apprehension activity has been handled in the experimental conditions. Under monotonous conditions worsening of the capacity for work (the increase of decision time and number of mistakes) has been shown to be correlated with the value of such electrophysiological indices as longevity of alpha-rythm blockade, amplitude and frequency amplitude characteristics of electroencephalogram, interhemispheric and central-occipital asymmetry coefficients, frequency and variability of heart-rate. The character of changes of electrophysiological indices depends on the individual psychophysiological characteristics.     

Dynamics of seated computer work before and after prolonged constrained sitting

This laboratory study investigated seated computer work before and after prolonged constrained sitting. Discomfort ratings and kinetic and kinematics data were recorded in nine healthy males performing computer work for 5 min before and after 96 min of sitting. The displacement of the center of pressure (CoP) in anterior-posterior and medial-lateral directions and lumbar curvature (LC) were calculated. The root mean square, standard deviation, and sample entropy values were computed from the CoPs and LC signals to assess the magnitude, amount of variability, and regularity of sitting dynamics, respectively. The discomfort increased for the buttocks (p = .02).The standard deviation and sample entropy values of the CoPs and LC signals, respectively, increased (p < .04) and decreased (p < .004) whereas the root mean square remained unchanged (p > .15) after prolonged constrained sitting compared with before. This present study showed that during seated computer work, prolonged constrained sitting affected the amount of variability and the regularity of sitting postural control, whereas the magnitude was not affected. The importance of the dynamics of sitting control may challenge the idea of a static and ideal seated posture at work.     

The evaluation and prognosis of the psychophysiological status of a human operator

In experiments on 56 healthy subjects (18-20 years old) the quality of their activity was determined during compensatory watching the mark at complicating regimes of work. Depending on the difficulty of the task five groups of subjects were singled out with optimum working capacity in one of four working conditions: normal, ordinary and strenuous work, model of stress situation. It is established that the change of the number of significant correlative connections between main parameters of psychophysiological state of man-operator reflects the condition of his functional systems. On the basis of computation of total range of organization values of both R-R intervals of the ECG and duration of expiration, the success of the man-operator work in complex conditions of activity is predicted.     

Continuous, intermitted and sporadic motor unit activity in the trapezius muscle during prolonged computer work.

The Cinderella hypothesis postulates the continuous activity of specific motor units (MUs) during low-level muscle contraction. The MUs may become metabolically overloaded, with the subject developing muscle pain and strain. The hypothesis requires MUs that are active for a time long enough to actually damage muscle fibers. The aim of this study was to determine if there are continuously active MUs in the right trapezius muscle during normal computer work using a computer mouse. Fourteen healthy subjects executed an interactive computer-learning program (ErgoLight) for 30 min. Six-channel intramuscular EMG and two-channel surface EMG signals were recorded from two positions of the trapezius muscle. Decomposition was achieved with automated, multi-channel, long-term decomposition software (EMG-LODEC). In two out of the 14 subjects, three MUs were continuously active throughout the 30 min. Although the majority of the MUs were active during only part of the experimental session, an ordered on-off behavior (e.g. substitution) pattern was not observed. As long-lasting activity was verified in some subjects, the results support the Cinderella hypothesis. However, it cannot be concluded here how long the MUs could stay active. If continuous activity overloads low threshold MUs, the potential exists for selective fibre injuries in low threshold MUs of the trapezius muscle in subjects exposed to long-term computer work.     

The indices of EEG spatial synchronization in normal 10- to 12-year-old schoolchildren and in learning difficulties]

10-12-year-old schoolchildren were divided into three groups: a normal one, a group with psychological problems, and a third one with medical problems. The EEG was recorded at resting and while reading a text. An obviously higher global spatial synchronisation was found in the normal group as compared with the "medical" one. In the "psychological" group, a diffuse hyperresponsiveness was found in the transition state from resting to activity. The above differences seem to be due to a morpho-functional immaturity and a functional insufficiency of two different portions of the brain ascending activating system. Evidently the "medical" group children have an immaturity of the bulbar and midbrain reticular formation, whereas the "psychological" group children have, probably, an immature diencephalic activating system (the thalamus).     

Parameters of the prestimulation EEG during operator recognition of a meaningful photic stimulus

Comparison of prestimulus EEG parameters with characteristics of recognition of a numeral stimulus showed that the complex of spatial-temporal parameters of the EEG of the operator reflects both the rate of success of the given activity and its quality. Functional state of CNS previous to optimal recognition (70% of efficiency, short reaction time), are characterized by mean level of spatial synchroneity of potentials in both cerebral hemispheres and by mean expressiveness of frequencies from 0.2 to 30 Hz in electrical activity of the majority of studied neocortical areas as compared with the states before recognition with prolonged reaction time and before non-recognition of the stimulus.