Date Published: May 23, 2019
Publisher: Public Library of Science
Author(s): Karin Valkenet, Cindy Veenhof, Jaroslaw Harezlak.
Hospital stays are associated with high levels of sedentary behavior and physical inactivity. To objectively investigate physical behavior of hospitalized patients, these is a need for valid measurement instruments. The aim of this study was to assess the criterion validity of three accelerometers to measure lying, sitting, standing and walking.
This cross-sectional study was performed in a university hospital. Participants carried out several mobility tasks according to a structured protocol while wearing three accelerometers (ActiGraph GT9X Link, Activ8 Professional and Dynaport MoveMonitor). The participants were guided through the protocol by a test leader and were recorded on video to serve as reference. Sensitivity, specificity, positive predictive values (PPV) and negative predictive values (NPV) were determined for the categories lying, sitting, standing and walking.
In total 12 subjects were included with a mean age of 49.5 (SD 21.5) years and a mean body mass index of 23.8 kg/m2 (SD 2.4). The ActiGraph GT9X Link showed an excellent sensitivity (90%) and PPV (98%) for walking, but a poor sensitivity for sitting and standing (57% and 53%), and a poor PPV (43%) for sitting. The Activ8 Professional showed an excellent sensitivity for sitting and walking (95% and 93%), excellent PPV (98%) for walking, but no sensitivity (0%) and PPV (0%) for lying. The Dynaport MoveMonitor showed an excellent sensitivity for sitting (94%), excellent PPV for lying and walking (100% and 99%), but a poor sensitivity (13%) and PPV (19%) for standing.
The validity outcomes for the categories lying, sitting, standing and walking vary between the investigated accelerometers. All three accelerometers scored good to excellent in identifying walking. None of the accelerometers were able to identify all categories validly.
Physical inactivity seems a worldwide epidemic [1;2]. More and more time is spend sitting while prolonged sitting is a risk factor for all-cause mortality, independent of physical activity [3;4]. Whilst this is a recognized problem in daily life, physical inactivity is also a problem within hospital settings [5;6]. The culture in hospitals is to reflexively put patients in their pyjamas in a bed once they are admitted [7–10]. As a result hospitalized patients currently spend 70–83% of the day lying in bed and less than 6% physically active [11–14]. This raises concerns as the dangers of bed rest are well known since decades [5–9].
A cross-sectional study was performed in a Dutch university hospital. Participants were eligible for inclusion when they stated that they were able to perform all tasks of a standardized protocol and that they were able to be physically active at moderate intensity for at least 30 consecutive minutes. The study protocol was approved by the medical ethical committee of the University Medical Center Utrecht. Written informed consent was obtained from all participants prior to the assessments.
Between April and July 2017, 12 subjects (9 male / 3 female) completed the structured protocol. Of them 4 were healthy subjects, 6 were outpatient subjects and 2 were inpatient subjects. The participants had a mean age of 49.5 (SD 21.5) years and a mean body mass index of 23.8 (SD 2.4) kg/m2.
The results of this study show that the validity of the ActiGraph GT9X Link, Activ8 Professional and Dynaport MoveMonitor is good to excellent for registering walking. The validity, based on the positive predictive values, of the ActiGraph and Activ8 is poor for lying and sitting, moderate for standing and excellent for walking. The validity of the Dynaport is poor for sitting and standing, and excellent for lying and walking.