[The correlation between the heart contraction rate and the operator's stress-resistance]

There is factual confirmation of the correlation between operator's stress-resistance and heart rate (HR). HR data alone without assessment of the job quality in a group of operators were enough to rank the operators by their resistance to stress. However, there are several requirements to be met. To begin with, operators should experience a weak or moderate mental stress that will modify HR. Secondly, other sympathetic influences should be reduced to a minimum, as they may mask the emotion-driven effects (motor activity, elevated tone of posture muscles, meals). With this in view, HR measurements are advisable during night sleep to escape, in addition, the endogenous sympathetic activation associated with ergotrophic metabolism. In the day time, HR should be measured after 10 to 15 minutes in recumbent position.