The effects of physical activities on cardiovascular variability in ambulatory situations [ECG/accelerometry analysis]

Cardiovascular variability is highly affected by changes in body posture and physical activity. Therefore, an objective tool to control for physical activity is necessary to study cardiovascular processes in real-life ambulatory situations. In an ambulatory study, accelerometry by means of body-mounted piezo-resistive sensors was used to quantify heart rate variability in relation to body posture (lying, sitting, standing) and physical activities (walking). Comparison of these data with posture-related heart rate changes obtained under standardized conditions revealed close correspondence, underlining the validity of the authors' ambulatory method. Application of the exponential time-frequency distribution to the authors' beat-to-beat heart rate time series further illustrated the complexity of the cardiovascular adjustments that occur during normal daily life activities.