Experiences of heart rate monitoring in observational and intervention studies.

Scientific demonstration of the health-enhancing eff ects, and the cardiovascular risks, of regular physical activity has created a need to characterize, in a quantitative manner, the intensity of physical activity in its various forms. Heart rate is one useful indicator because of its known predictable and reproducible relationships, within certain limits, to energy expenditure and cardiac load or strain. The development of versatile ambulatory heart rate monitoring devices expands the possibilities to assess the intensity and cardiac strain of various types of physical activity in natural settings. The examples cited in this paper demonstrate that ambulatory heart rate monitoring is an accurate, reliable, non-obtrusive and socially acceptable technique in a variety of conditions. It is relatively inexpensive and easy to use by both the experimental subjects and the research personnel, and it provides large amounts of data for versatile processing and display by ordinary equipment.