Objective: To assess the impact of non-invasive ambulatory blood pressure monitoring on physical activity measured objectively by triaxial accelerometers.

Method: Twenty four working men and women carried out ambulatory blood pressure plus activity monitoring for a working day and evening, and activity monitoring alone for a separate day and evening. Blood pressure measures were taken at 20 minute intervals during the day and 30 minute intervals in the evening, and were accompanied by diary assessments of mood, location and posture. Comparisons were made of energy expenditure on the two days, and activity levels during the minutes surrounding each blood pressure reading and diary completion.

Results: Energy expenditure assessed in terms of activity calories per hour were significantly lower during blood pressure plus activity monitoring compared with activity monitoring alone (43.0 vs 37.3 Kcal). Energy expenditure was lower during the four minutes surrounding each blood pressure reading than the intervals between blood pressure readings. However, any energy expenditure was also lower in the intervals between blood pressure readings than during comparable times on the activity only monitoring day. Blood pressure, heart rate and physical activity were moderately correlated within individuals.

Conclusions: Ambulatory blood pressure recording using automated sphygmomanometers is associated with reduced physical activity during the monitoring day. This is due partly to regular periods of immobility during cuff inflation and deflation and diary completion, and partly to more general self-imposed restrictions on activity. This pattern has implications for the representativeness of ambulatory blood pressure monitoring, and the construction of ambulatory monitoring diaries.