Can an Accelerometer-Based Monitor be used to Accurately Assess Physical Activity in a Population of Survivors of Critical Illness?

PURPOSE: To investigate the validity and reliability of the Activity Monitoring Pod (AMP331) to record gait parameters in healthy young adults (YA) and intensive care unit inpatients (ICU). METHODS: YA (N=15) completed a series of over-ground walks. Another 15 YA completed a series of treadmill walks. The ICU group (N=20) completed a series of over-ground walks with repeat trials. Gait parameters were recorded simultaneously by the AMP 331 and the Vicon (YA) and the AMP 331, direct observation and a stopwatch (ICU). RESULTS: For the YA over-ground, no significant differences were found between the measures recorded by the systems. For the YA treadmill, 43% of the measures differed (P < .05). For the ICU group, the AMP331 underestimated distance and speed by 3m and 25cm/s respectively. Reliability measures (ICU group) for distance (ICC 0.99, 95%CI 0.98 – 0.99) and step count (ICC 0.99, 95%CI 0.99 – 1.00) were excellent. CONCLUSIONS: The AMP 331 is a valid instrument for recording basic gait parameters for over-ground walking in healthy YA and ICU survivors.