Research Study Abstract

A study investigating the validity of an accelerometer in quantification of step count in adult hospital inpatients recovering from critical illness

  • Published on February 14, 2019

To determine the validity of the ActiGraph GT3X accelerometer in step count quantification when compared to observed step count in hospitalised adults recovering from critical illness.

Large National Health Service (NHS) Hospitals Trust.

In total, 20 hospital ward-based adults (age: mean 62.3, SD 11.5) who had required greater than 48 hours of mechanical ventilation in the intensive care unit.

Main measures
Participants walked self-selected distances and speeds as part of a semi-structured movement protocol not exceeding 3 hours. Two ActiGraph GT3X accelerometers were worn, one on the thigh and one on the ankle of the non-dominant leg. Accelerometer-recorded step counts were compared against observed step counts.

In total, 31 separate walking episodes were analysed. A mean (SD) of 45.87 (±19.72) steps was calculated for observed step count (range 15–90). Mean differences (95% limits of agreement) of −0.84 steps (−3.88 to 2.2) for the ankle placement and −17.7 steps (−40.63 to 5.25) for the thigh were calculated. Intraclass correlation coefficients (95% confidence intervals) of 0.99 (0.99 to 1.0) and 0.46 (−0.1 to 0.78) were determined for the ankle and thigh, respectively. Placement sites were well tolerated by 95% of participants.

An ankle-mounted ActiGraph GT3X accelerometer demonstrates validity in quantification of step count in hospitalised adults recovering from critical illness. A thigh placement was not considered valid.


  • Jayne Lesley Anderson 1,2
  • L Samantha Yoward 2
  • Angela J Green 1


  • 1

    Physiotherapy Department, Therapies Centre, Hull Royal Infirmary, Hull and East Yorkshire Hospitals NHS Trust, Hull, UK

  • 2

    School of Health Sciences, York St John University, York, UK


Clinical Rehabilitation


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