CONTROL OVER WORK PACE, JOB STRAIN AND CARDIOVASCULAR-RESPONSES IN MIDDLE-AGED MEN

Objective: To assess the effects of control over work pace on cardiovascular stress responses in healthy middle-aged men. Design: The study involved administration in the laboratory of visual matrix and mirror drawing tasks, the pace of tasks being either under the control of the subject (self-paced) or determined externally (externally paced). The work demands in the two conditions were equated. Method: Forty men aged 55-65 years were randomly assigned to self-paced or externally paced conditions. Blood pressure (recorded continuously using the Finapres), heart rate, cardiac baroreflex sensitivity, salivary cortisol, skin conductance and breathing pattern were monitored at rest, during task performance and at recovery following tasks. Results: Blood pressure and heart rate responses were significantly greater under the externally paced than self-paced conditions. The mean increase in blood pressure during the visual matrix task averaged 19.8/9.4 versus 34.1/15.5 mmHg for the self- and externally paced conditions, and 28.2/13.7 versus 41.8/19.5 mmHg in response to mirror drawing, respectively. Performance of the matrix task was less accurate under externally paced than self-paced conditions, but the two groups did not differ in mirror drawing. A reduction in baroreflex sensitivity and increases in cortisol, respiration rate, tidal volume and skin conductance responses were recorded during tasks, but these responses did not distinguish the two groups. Men were divided on the basis of reported job strain associated with their regular work, using the demand-control model. Blood pressure and heart rate responses were particularly pronounced among men reporting high job strain who were allocated to the externally paced condition. Conclusions: Middle-aged men showed greater stress-related cardiovascular responses when they performed tasks at a pace that they could not control. This pattern may be relevant to the mechanisms through which job strain (high demands associated with low control) influences cardiovascular disease risk.