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

Objective: To assess the effects of control over work pace on cardiova scular 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 ag ed 55-65 years were randomly assigned to self-paced or externally pace d 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 external ly paced than self-paced conditions. The mean increase in blood pressu re during the visual matrix task averaged 19.8/9.4 versus 34.1/15.5 mm Hg for the self- and externally paced conditions, and 28.2/13.7 versus 41.8/19.5 mmHg in response to mirror drawing, respectively. Performan ce of the matrix task was less accurate under externally paced than se lf-paced conditions, but the two groups did not differ in mirror drawi ng. A reduction in baroreflex sensitivity and increases in cortisol, r espiration rate, tidal volume and skin conductance responses were reco rded during tasks, but these responses did not distinguish the two gro ups. Men were divided on the basis of reported job strain associated w ith their regular work, using the demand-control model. Blood pressure and heart rate responses were particularly pronounced among men repor ting high job strain who were allocated to the externally paced condit ion. Conclusions: Middle-aged men showed greater stress-related cardio vascular responses when they performed tasks at a pace that they could not control. This pattern may be relevant to the mechanisms through w hich job strain (high demands associated with low control) influences cardiovascular disease risk.