A test of generalizability of cardiovascular reactivity using a controlled ambulatory procedure

This study tested the hypothesis that reports of poor generalizability of cardiovascular reactivity measured in the laboratory to changes observed during everyday life are due to a lack of standardization of activities and position (sitting, standing) in the latter situation. Thirty-seven subjects engaged in reactivity testing, and then in a 4-hour series of standardized activities outside the laboratory (controlled ambulatory phase), accompanied by the experimenter, on each of 2 days. The controlled ambulatory activities included alphabetizing, an editing task, a brisk walk, solving word puzzles, and eating lunch. Two measures of field variability were examined: the standard deviation and the root mean square of successive differences, of all ambulatory measurements. Associations between laboratory change scores and measures of field variability were poor (highest r = .23). We conclude that evidence for generalizability of reactivity change scores remains poor, and cannot be solely attributed to the uncontrolled nature of activities in the field.