In briefPhysical activity patterns of 59 children were determined by recording heart rates before and during an exercise intervention program for coronary heart disease risk. Twenty-six children engaged in 25-minute aerobic activity sessions four days a week for eight months; the control group took regular physical education classes. Baseline data revealed that both groups had similar activity patterns, that the children seldom attained a heart rate greater than 160 beats min-1, and that the boys expended significantly more energy per day than the girls. The activity patterns of children in the experimental group improved significantly.