Determinants of ambulatory blood pressure response to physical activity

OBJECTIVES: Previous studies reported that the association between physical activity, measured with a wrist-worn accelerometer, and ambulatory blood pressure is rather weak and that the inter-individual variation in the degree of association is high. The aim of the present study was to quantify the responses of ambulatory blood pressure (BP) and heart rate (HR) to physical activity, and to determine the effect of age, gender, body mass index, mean BP and HR level and the use of antihypertensive medication on these responses. PATIENTS AND METHODS: Twenty-seven subjects (24 hypertensive) underwent 24-h ambulatory monitoring of BP, HR and physical activity. Physical activity was measured with four accelerometers mounted on the trunk and legs. The daytime BP and HR responses to physical activity and the possible modulating effects of the various subject characteristics on these responses were estimated with Random Regression Models. RESULTS: Increasing physical activity from a very low level (e.g. watching television) to a moderate level (e.g. shopping) caused an average response of systolic blood pressure (SBP) of 11.6 mmHg, of diastolic blood pressure (DBP) of 7.0 mmHg and of HR of 16.1 beats/min. The SBP response to activity was about 2 mmHg larger for the overweight subjects than for subjects with normal weight, and the SBP, DBP and HR responses increased about 0.8 mmHg, 0.6 mmHg and 0.7 beats/min, respectively, with every 10 years increase in age. The between-subjects variances in estimated responses were low and were almost completely explained by differences in overweight and age between subjects. The average within-subject variances, however, were high. CONCLUSIONS: Normal daily physical activity explains only a small part of the BP and HR variability. The BP and HR responses to activity are modestly affected by age. Overweight has a small effect on the SBP response to activity.