EFFECTS OF BRIEF REST PERIODS UPON HEART-RATE IN MULTIPLE BASE-LINE STUDIES OF HEART-RATE REACTIVITY

Although there has been some discussion regarding the appropriate time necessary for subjects to reach true resting heart rate prior to expe rimentation, the relevance of conclusions from that discussion for mul tiple baseline studies of heart rate has not been demonstrated. To inv estigate this issue, data were collected from 39 males and 33 females following a standard 15-minute adaptation period and then during a ser ies of two-minute experimental phases including stressor tasks and res t periods. Results indicated that, while the group's heart rate during brief rest periods returned to postadaptation levels, there was a sub stantial subgroup of subjects for whom this was not the case. Implicat ions for the use of multiple baseline procedures in research where hea rt rate is the dependent variable are discussed.