Cardiovascular and electromyograph effects of low and high density work on an interactive information system

Abstract Sixteen males and 16 females solved 80 database queries presented on a visual display terminal (VDT). A solution required the correct selection of three successive hypertext indices hierarchically structured from the query to the data answer. Under a low density work condition, each selection of a hypertext index was followed by a 10-s delay before another database level, consisting of both indices and data, was presented. Under a high density work condition, each selection of a hypertext index was followed by a 1-s delay before another database level, consisting of both indices and data, was presented. To avoid a reduction in earnings, a solution criterion was 50 s for the low density condition, and 20 s for the high density condition. Forty successive queries were presented under each condition, and the order of conditions was counterbalanced across subjects. Systolic and diastolic blood pressure, mean arterial blood pressure, heart rate, and masseter electromyograph (EMG) responses showed elevations during task performance, in comparison to a resting baseline. Systolic blood pressure was higher during the high density condition in comparison to the low density condition, but masseter EMG activity was reliably higher only for females. Systolic blood pressure differences between the low and high density conditions were reliable over several successive performance sessions presented to two individual subjects. Subjects' scores on the Structured Interview (SI; Friedman & Powell, 1984) were found to relate to systolic blood pressure.