When to measure resting values in studies of children's cardiovascular reactivity.

Investigations suggesting that the order of obtaining resting and cardiovascular reactivity measurements moderates values have provided inconsistent results and have not analyzed data from children; the generalizability of results is uncertain. In this investigation, all children enrolled in the eighth-grade classrooms of the public schools of an entire county (n = 451) participated in standardized reactivity assessments. The order of resting and reactivity measurements was randomized by examination day (a total of 19 days). Analyses indicated that all comparisons of order effects on mean resting blood pressure and heart rate, as well as reactivity (both change from resting and absolute values and both mean and maximal values), were nonsignificant. Results indicate that measurement order is not always a necessary consideration in studies of reactivity; the conditions under which measurement order is a consideration requires clarification.