Practical aspects of identifying and correcting worksite stress in post-infarction patients returning to work.

The authors propose a dynamic 'man-work system' model, centered around the bodily strain, which is determined jointly by the momentary efficiency of the organism and the sum of stresses acting at a given point of time, i.e. integrated along various durations. With regard to stresses, they call attention to the heuristic significance of a separate subgroup, that of physiological stresses and also to the necessity of the distinction of a physiological subclass in the class of information stresses. The 'man-work system' is completed by positive and negative feedback from the strain and the components of efficiency, thereby providing the basis of successful or unsuccessful adaptation of the organism to the short- and long-term challenges. The authors are of the opinion that the system offers a sounder foundation for rehabilitative as well as preventive cardiology.

Shoulder strain in keyboard workers and its alleviation by arm supports.

Keyboard work consists mostly of dynamic contractions of the small muscles of the forearms and hands. This is accompanied by continuous activity in the arm, shoulder and neck muscles keeping the head and hand in the correct position. Eliminating the weight from the arm by means of support and the position of the arms influences the electrical activity of shoulder muscles when working at a keyboard. We studied the influence of elbow angle; as well as that of different arm supports, on electrical activity of upper trapezius muscle during keyboard work in healthy workers and persons suffering from shoulder pains. The measurements were carried out in the laboratory. EMG activities, which where measured as mean square root (RMS)-values at every 100-millisecond period in trapezius muscle when working, were lower, the greater the elbow angle. Furthermore electrical activity decreased when subjects used arm supports while working. It is evident that the static load to shoulder muscles can be lowered significantly in keyboard work, when the forearms are at an angle of at least 100 degrees and by using arm supports. The most convienient and ergonomic working position can also be found individually be the method used here.

Organization of blood pressure reflexes elicited by low intensity stimulation of cutaneous and muscular afferents in cats.

The incidence and patterns of blood pressure reflexes elicited by sustained (3--4 min) low intensity electric stimulation (0.5--4 V, 0.1 ms, 4 Hz) of cutaneous and muscular afferents of high or low spinal segmental input levels were investigated in immobilized (gallamine) and artificially ventilated conscious or anaesthesized (chloralose-urethan) cats. In a part of the experiments, subconvulsive doses of picrotoxin and/or strychnine were used as pharmacological disinhibitors. The results suggest that (1) the variability of the responses in conscious animals may be due to the varying degree of spinal inhibition, especially of that associated with cutaneous inputs; (2) intraspinal irradiation of excitation plays an important role in the integration of the reflexes; (3) the preferred direction of irradiation seems to be different in the projection zones of cutaneous and muscular afferents. Comparison of the results with previous data points to the possibility that the different response patterns seen after intense stimulation might be the result of the suppression of spinal inhibitions, due to C-fibre activation.

Characteristics of blood pressure and nictitating membrane reflexes elicited by electric stimulation of sciatic nerve in conscious and in anaesthetized cats.

Blood pressure (BP) reflexes and contractions of the nicitating membrane (NM) elicited by sustained (60 sec) stimulation of the sciatic nerve have been simultaneously recorded in gallamine immobilized conscious cats and following the administration of chloralose-urethane (50 and 300 mg/kg, respectively). By varying the stimulation parameters in a wide range, voltage and frequency characteristics of BP and NM reflexes have been plotted. In order to reduce the great number of possible BP-characteristics, the "dose" of stimulation (the product of voltage, impulse duration, frequency and of the stimulation period) has been introduced to plot "dose"-response curves. Differences in the BP and NM responses, and between awake and anaesthetized states as well as their probable causes are discussed. On the basis of the characteristic curves, a complex consisting of two facilitatory and at least one inhibitory mechanism has been supposed to be involved in the CNS integration of somato-sympathetic reflexes.