Introduction Conventional catheter-based systems used for ambulatory oesophageal pH monitoring have been reported to affect patient behaviour. As physical activity has been associated with gastro-oesophageal reflux disease (GORD), there is a risk that abnormal behaviour will degrade the value of this diagnostic investigation and consequent management strategies. Our aim was to provide the reporting physician with objective peri-investigational changes in activity, and the means to assess the association between activity and pH during the test, using a wearable activity monitor.