Criterion Validity of the Actigraph GT3X Accelerometer in Determination of Body Position and Walking in Hospital Ward Patients Recovering From Critical Illness
Phase: NA
Conditions: Critical Care, Walking, Posture
Sponsor: Hull University Teaching Hospitals NHS Trust

                    
 
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METHODOLOGICAL PROTOCOL 
Criterion validity of the Actigraph GT3X accelerometer in determination of body 
position and walking in hospital ward patients recovering from critical illness 
 
Protocol details 
Version 1 01/04/2016 
 
Name, role and contact details of Chief Investigator: 
Mrs Jayne Anderson 
Lecturer Practitioner Physiotherapist / 
PhD Student  
Therapies Centre 
 
 
 
Faculty of Health and Life Sciences 
Hull Royal Infirmary  
 
 
De Grey Building 
Anlaby Road  
 
 
 
York St John University 
Hull 
 
 
 
 
 
Lord Mayor's Walk,  
HU3 5JZ 
 
 
 
 
York 
YO31 7EX 
Tel: 01482 605293 
 
 
 
 
 
 
Signature 
      
 
Date  12th April 2016 
 
 
 
Study Site 
 
 
Study Sponsor 
 
 
 
Hull and East Yorkshire 
Mr James Illingworth 
Hospitals NHS Trust   
Research and Development Manager 
 
 
 
 
Hull and East Yorkshire Hospitals NHS Trust 
 
Castle Hill Hospital 
 
2nd Floor Daisy Building 
 
 
Castle Road 
 
 
Castle Hill Hospital 
 
 
 
Cottingham 
 
 
Cottingham 
 
 
 
East Yorkshire 
 
East Yorkshire  
HU16 5JQ 
 
 
East Yorkshire 
 
 
 
 
HU16 5JQ 
Hull Royal Infirmary  
Tel: 01482 461903  
Anlaby Road  
 
Hull 
 
 
 
  
HU3 5JZ 
 
 
 
Tel: 01482 605293 
 
 
 
 
 

                    
 
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List of abbreviations and definitions 
BMI  
 
Body Mass Index 
CI 
 
 
Chief Investigator 
HLS  
 
Faculty of Health and Life Sciences 
HEYHT 
 
Hull and East Yorkshire Hospitals NHS Trust 
ICU      
 
Intensive Care Unit 
ICUAW 
 
Intensive Care Unit Acquired Weakness 
IG 
 
 
Information Governance 
IRAS  
 
Integrated Research Application System 
LOA  
 
Limits of agreement 
UoL 
 
 
University of Leeds 
UK 
 
 
United Kingdom 
YSJU  
 
York St John University 
 
Background information and rationale 
Physical recovery following critical illness is often complicated by profound muscle 
weakness, referred to as intensive care unit acquired weakness (ICUAW). ICUAW 
negatively impacts on the time taken to wean patients from ventilator support, 
precipitating significant mobility and functional impairment (Latronico et al., 2012, 
Latronico and Bolton, 2011, Deem et al., 2003). Functional impairment; impacting 
negatively on quality of life, may continue for years following discharge from hospital 
(Herridge et al., 2011, Cheung et al., 2006, Herridge et al., 2003).  
Research has investigated how the negative effects of functional impairment 
may be attenuated. Early mobility interventions, commencing in the intensive care unit 
(ICU), including sitting over the edge of the bed, sitting to standing, bed to chair 
transfers and walking variable distances may reduce the severity of ICUAW (Morris et 
al., 2011, Schweickert et al., 2009, Needham, 2008). These interventions are safe, well 
tolerated and effective, even when patients are on ventilator support (Adler and Malone, 
2012). This evidence supports the instigation of early activity and the development of 
more formal mobility protocols for those recovering from critical illness.  These 

                    
 
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methods are only effective if all members of the health care team promote activity 
within ICU and upon a patient’s return to the ward. What is desirable therefore is the 
multi-disciplinary adoption of a rehabilitation ‘culture’ inherent within this patient 
population.  
Research evidence suggests that a culture which encourages early activity within 
the ICU is not universally adopted (Berney et al., 2015, Nydahl et al., 2014, Berney et 
al., 2013). Absence of a rehabilitation culture within the hospital ward environment is 
provided from a number of observational studies. A decrease in the distances mobilised 
compared to those undertaken within ICU in the first 48 hours on the ward has been 
reported (Hopkins et al., 2012). Time delays have been described in patients 
undertaking the same mobility interventions that were performed within the ICU, for 
example getting out of bed to sit in a chair (Pandullo et al., 2015).   Finally, a study 
reported that patients were still spending 90% of the day inactive in lying or sitting 
positions in the final two days prior to discharge from hospital (Borges et al., 2015). 
These findings persist despite evidence reporting early mobilisation attenuates 
neuromuscular weakness and is linked to both a reduction in readmission and death 
within the first year following discharge (Morris et al., 2011, Schweickert et al., 2009, 
Needham, 2008).  What is desirable may not always be achievable however, with 
barriers impacting on patients’ ability to resume activity upon transfer to the ward; 
including health care resources and time of transfer (Pandullo et al., 2015). 
The last few days before hospital discharge is possibly the final opportunity 
patients’ will access rehabilitation services administered by health care professionals. 
Surveys report only 27% of NHS adult ICU’s across the United Kingdom (UK) have 
formal post discharge services for patients who have experienced critical illness 
(Connolly et al., 2014). Only 7% offer specific post discharge rehabilitation 
programmes; not all on a regular basis, with ‘funding’ being the most often barrier.  
Consequently, there is a need to ensure patients feel empowered with confidence, 
motivation and the physical abilities essential to continue progression of functional 
recovery after discharge. This is especially important where formal follow up services 
are not accessible.  
Formal follow up services post discharge are rare (Connolly et al., 2014). This 
presents a need for closer monitoring of physical activity in hospital during recovery 
from critical illness in order to identify those requiring most support and health resource 

                    
 
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input. This will identify those patients who although functionally able to undertake 
activity independently, may lack the confidence or motivation to do so. If not addressed, 
this may continue following discharge from hospital, negatively impacting on further 
functional recovery and quality of life (Herridge et al., 2011, Cheung et al., 2006, 
Herridge et al., 2003). Subjective methods exist for monitoring activity levels within the 
hospital environment but they are subject to both methodological and operational 
weaknesses.  Whilst direct observation permits the ability to monitor and record the 
specific type and duration of activity being undertaken (Patterson et al., 2005), it is time 
consuming and not a viable option to undertake as part of a daily routine for individual 
patients due to resource intensity (Cheung et al., 2011). As patients become able to 
undertake more activity under their own volition, it may not be documented as a result 
of it not being witnessed. Physiotherapy or occupational therapy documentation only 
provides a brief snapshot of activity, with studies in other hospital populations reporting 
these sessions only account for 0.5 and 0.6% of the day (Patterson et al., 2005).  
Therefore, whilst direct observation has proved useful for research purposes (Berney et 
al., 2015, Patterson et al., 2005), it is not feasible as a method of activity monitoring 
within a busy clinical environment.   
Another method of activity monitoring is patient self-report; but evidence 
suggests patients may fail to accurately report activity levels and abilities (Cheung et al., 
2011, Prince et al., 2008, Sager et al., 1992). Self- report tools in adult populations are 
based on subjective feedback, show generally low to moderate correlations with more 
directly measured activity and may fail to register low intensity activities undertaken 
within ‘frail’ populations (Prince et al., 2008).  Patients recovering from critical illness 
also often experience cognitive impairment affecting the ability to recall information 
required for self-report measures (Pandharipande et al., 2013).  Both observation and 
self – report rely on individuals to subjectively record or remember activity undertaken. 
It requires those assimilating the information to consciously register that activity is 
being undertaken in order to capture and record it, which is not always the case (Cheung 
et al., 2011, Prince et al., 2008, Sager et al., 1992).  This evidence suggests that both 
methods may be unsuitable for monitoring activity within patients recovering from 
critical illness. Moreover, both are prone to methodological and operational weaknesses, 
which may adversely affect their validity and reliability for use within this setting. 
 
 

                    
 
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The use of technology to monitor activity levels within the hospital environment.  
 
Due to the operational and methodological inadequacies of direct observation and 
patient self-report to accurately monitor activity levels within the hospital environment, 
other approaches must be considered. Methods of activity monitoring should be 
explored which relinquish the operational demands on individuals and embrace 
objective and quantifiable methods which demonstrate validity and reliability within a 
specific setting.  
 
There is continued interest in the validation of small, wearable activity monitors 
to capture activity, especially in elderly hospital inpatient populations (Pedersen et al., 
2013, Taraldsen et al., 2011, Culhane et al., 2004). These devices permit quantification 
of both the type and amount of activity undertaken though a typical day. Evidence 
suggests that these small dimension, lightweight, measurement devices demonstrate 
validity and reliability dependent on the task being analysed and where the sensors are 
applied (Cuesta-Vargas et al., 2010).  
 
To date, only two studies have investigated the validity of activity monitors in 
quantification of purposeful activity undertaken by patients recovering from critical 
illness (Edbrooke et al., 2012, Winkelman et al., 2005). Both of these studies were 
undertaken within the ICU. No studies have investigated the validity of activity 
monitors to quantify activity upon return to the ward as functional ability improves.  
The aim of this study therefore is to investigate the validity of a specific activity 
monitor, the Actigraph GT3X accelerometer (Actigraph LLC, Pensacola, Florida, USA) 
in identifying activities and adoption of certain body postures in patients recovering 
from critical illness within the hospital ward environment.  
 
The Actigraph GT3X accelerometer  
 
One example of an activity monitor is an accelerometer, which detects movement by 
sensing changes in the speed and direction of acceleration, capturing it as a numerical 
‘count’.  As movement intensity increases, there is a corresponding increase in 
numerical count; the higher the count, the more intensive the activity. Information on 

                    
 
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activity is captured over a specific time period, called an epoch, which can be 
programmed onto the devices.  An epoch can capture activity undertaken over less than 
a second to over a number of minutes (Actigraph, 2009).  Accelerometers have the 
capacity to continuously capture data over a number of days if necessary, depending on 
the measurement modes used, for eventual download onto a computer.  Data is captured 
in real time (as it happens), permitting the ability to identify the actual duration of 
activity (or inactivity) and when it occurred.  
 
The Actigraph GT3X accelerometer contains measurement modes which 
quantify physical activity intensity (registering a numerical ‘count’), body position via 
an inclinometer (lying, sitting or standing) and step count.  Studies have shown good 
inter-instrument reliability in this particular make and model (Santos-Lozano et al., 
2012). These measurement modes could permit objective, unobtrusive monitoring of all 
purposeful activity undertaken during the day by those recovering from critical illness 
in hospital. Activity may involve a postural change (sitting to standing for example), 
walking independently or with assistance (mobilisation) and other generalised physical 
activity.  It could also identify where prolonged periods of inactivity are being observed, 
assisting in identifying individuals who may lack confidence or motivation, despite 
being able to undertake movement under their own volition. If used in this way, the 
Actigraph GT3X could assist in the effective allocation of rehabilitation resources, 
identifying those who may require increased input to achieve their rehabilitation goals.  
To date, no research has been undertaken to determine whether the Actigraph GT3X 
accelerometer is a valid instrument to assess body position, step count or generalised 
activity within a population recovering from critical illness. Despite this, recent research 
has used this model to objectively quantify activity levels in patients resident in the 
ICU, using both the inclinometer (body position) and activity count settings (Schujmann 
et al., 2015). The study by (Schujmann et al., 2015) placed the accelerometer on the 
ankle. Although manufacturer’s recommend that this device is worn around the waist 
(Actigraph 2009), encouraging results have been found with an ankle placement, 
particularly in determination of step count (Korpan et al., 2015).   It is important 
therefore to determine the validity of this particular device and its optimum body 
placement site within a patient population recovering from critical illness.     

                    
 
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A feasibility study undertaken by the chief investigator (CI), as part of a PhD 
programme of study, determined that an ankle placement of the Actigraph GT3X 
accelerometer was superior to the waist for determination of body position and step 
count. In this study, thirty healthy adult volunteers simulated patients weakened by 
critical illness. They performed a movement protocol which incorporated the typical 
activities undertaken by patients recovering in hospital from critical illness. These 
included moving from lying to sitting, sitting to standing (and vice versa) and walking 
short distances. Video recordings were taken of each participant during the movement 
protocols, enabling observation of the body positions adopted and step counting during 
the walking activities. Video recording was used as the criterion measure for 
comparison against the data captured by the accelerometers worn both at the ankle and 
the waist.  The activities detailed above are typically included within early mobility 
protocols which have undergone evaluation within populations experiencing critical 
illness (McWilliams et al., 2015, Adler and Malone, 2012, Schweickert et al., 2009).  
Moderate agreement (ĸ = 0.43, p < 0.001), was found between observation of video 
recordings of body position (lying, sitting or standing) and the inclinometer setting for 
the ankle placement. Fair agreement only (ĸ = 0.21, p < 0.001) was found for the waist 
placement. Regular misclassification of all body positions was found with the waist 
placement. The ankle placement identified both the lying and standing positions well. 
The sitting position however was only correctly identified intermittently for the ankle 
placement.  A novel finding emerged from this research relating to the ankle placement 
site. When a side lying position was adopted, the ankle accelerometer inclinometer 
function regularly registered a ‘0’. The ‘0’ setting normally corresponds to a ‘not being 
worn’ option. When a reading of ‘0’ was recoded to the option ‘side lying,’ agreement 
improved from ĸ = 0.43 (p < 0.001) to ĸ = 0.48 (p < 0.001). This finding suggests a new 
way of interpreting the ‘0’ reading of the inclinometer when worn on the ankle, which is 
worthy of further investigation within an actual patient population.  
The inconsistency of correct determination of body position of this 
accelerometer model when worn around the waist has been demonstrated by other  
authors (Berendsen et al., 2014, Hänggi et al., 2013). The inconsistency of correct 
identification of the sitting position in particular was highlighted by (Hänggi et al., 
2013). Other researchers have investigated ways of improving the ability to correctly 
classify the sitting position (Skotte et al., 2014).  The study by (Skotte et al., 2014)  

                    
 
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determined that the addition of a second Actigraph GT3X accelerometer placed on the 
mid-thigh yielded excellent results in detection of the sitting position. Pressure sensors 
in subjects’ hip pockets were used as a criterion measure to classify body position.  
As mentioned previously, the feasibility undertaken by the CI determined that 
the ankle placement was superior to the waist for recognition of step count. When 
walking a ten metre distance with a walking aid, using observed step count as a criterion 
measure the ankle placement demonstrated a mean difference -1 step, (Limits of 
Agreement (LOA) +3 to -5 steps) compared to the waist placement (mean difference -7 
steps, LOA +9 to -23 steps).  These positive findings for step count for the ankle 
placement are supported by a recent study cited earlier using a similar Actigraph model 
investigating the accuracy of step count in older adults (Korpan et al., 2015).   
Defining the research question  
Using the findings from the feasibility study regarding the ankle placement of the 
Actigraph GT3X accelerometer and the research cited suggesting improved 
classification of the sitting position with the addition of a thigh mounted accelerometer 
the following research question is proposed: 
Can an Actigraph GT3X accelerometer, placed at the ankle and thigh of the same leg, 
accurately measure body position and walking episodes undertaken by patients 
recovering from critical illness in a hospital ward? 
 
A number of study objectives evolve from this research question, assisting in the 
development of the methodological processes required to answer it.  
 
1. To determine the criterion validity of the ActiGraph GT3X accelerometer in 
detection of body position and step count when positioned either on the mid-thigh or 
ankle of the same leg.  
2. To establish if there is a superior single body placement site (thigh or ankle) to 
objectively record body position and step count within this patient population.  
3. To investigate the criterion validity of the combination of thigh and ankle 
accelerometer inclinometer outputs to correctly determine the sitting position. This 

                    
 
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will determine whether an algorithm can be constructed using the two inclinometer 
readings, which will better distinguish the sitting from the standing position.   
4. To evaluate, from a user perspective, the acceptability of these devices in relation to 
the placement sites used. This will be achieved by asking patients to score the 
answer to a particular question through the use of a Likert scale. The question is: 
o How would you rate the comfort of wearing the accelerometers? 
In consideration of the results from the feasibility study undertaken by the CI and 
research using the addition of a thigh mounted accelerometer to identify the sitting 
position (Skotte et al., 2014), the following hypotheses can be constructed: 
Hypotheses 
1. An ankle mounted Actigraph GT3X accelerometer, will accurately identify both 
the lying and standing positions when compared with direct observation as a 
criterion measure.   
2. An ankle mounted Actigraph GT3X accelerometer, will capture a step count 
comparable to that recorded by direct observation in a population resident on a 
hospital ward recovering from critical illness. 
3. The combination of inclinometer outputs of both the thigh and ankle placement 
sites will permit development of an algorithm permitting the ability to better 
distinguish between the sitting and standing position.  
4. The ankle and mid-thigh accelerometer placement sites will be well tolerated by 
patients recovering on a ward from critical illness.   
Subject selection and involvement 
The study will invite adult hospital ward patients recovering from critical illness to wear 
one Actigraph GT3X accelerometer on the antero-medial mid-thigh and another on the 
ankle, resting above the lateral malleolus of the same leg. The accelerometers will be 
worn for a period of time not exceeding three hours. Each device will be attached with a 
single patient use broad elastic belt, secured by Velcro fastening, using a standardised 
placement protocol. The non – dominant leg will be the preferred placement side.   

                    
 
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Participants will be asked to undertake a semi - structured movement protocol, 
consisting of low intensity movements typical of those that they will already be taking 
through the day. These include lying in bed, getting out of bed to sit over the side, 
moving from sitting to standing, sitting in a chair and walking distances that their 
current level of physical ability permits. The observation period will be undertaken at a 
time mutually agreed between the participant and the observer (the CI). Observation 
periods will not occur over lunchtimes or protected patient rest periods, which vary 
from ward to ward. Rest periods will be encouraged if required and should the 
participant request them.  
Participants will determine the order in which they perform the movements, but as 
many as possible must be completed within a period not exceeding three hours. It is 
envisaged this will reduce bias due to order effects and enable the determination of 
accelerometer validity in as naturalistic conditions as possible, whilst also permitting 
participant autonomy.  
Inclusion Criteria 
 18 years of age or above.  
 Ventilated in excess of 48 hours during admission in the ICU 
 Currently resident on a hospital ward (secondary care) following step down from 
ICU 
 At a stage in recovery where individuals are able to undertake all postural transfers 
independently or with minimal assistance (one person only) 
 Able to mobilise short distances, either independently or with assistance from a 
walking aid or one person 
 Willing to permit application of two Actigraph GT3X accelerometer devices, one 
lying anteromedially around the non-dominant mid-thigh; the other resting above 
the lateral malleolus on the same (ipsilateral) leg. Each device weighs 27g with 
dimensions of 3.8cm x 3.7cm x 1.8cm.  
 Participants must be willing to consent to a period of direct observation for a length 
of time not exceeding three hours, which will take place at a mutually agreed time. 
Observation will serve as the criterion measure which accelerometer data will be 
compared against. 

                    
 
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Exclusion Criteria 
 Unable to provide informed written consent, or unwilling to consent to a period of 
observation not exceeding three hours.  
 Those unable to make an informed decision about participation or demonstrating an 
inability to interpret information or follow study instructions as a result of impaired 
cognitive function. 
 Significant neurological or coordination impairment rendering it not possible to 
undertake purposeful movements independently or with minimal assistance, either 
of one person or with walking aids if walking.  
 Unable to speak/ understand English. This research forms part of a PhD programme 
of study and receives no funding to enable the use of language interpreter services or 
translation of study documentation (e.g. information sheet and consent form) into 
different languages. 
 Clostridium Difficile, similar infection or unmanaged urinary incontinence, due to 
potential contamination of the accelerometers if leakage into the internal mechanism 
occurs.     
 Evidence/ diagnosis of peripheral vascular disease.  
 Lower limb amputation 
 Polytrauma which prevents the adoption or normal lying, sitting or standing 
postures, or placement of the accelerometers according to the placement protocol.   
Recruitment of study participants 
Study participants will be resident on a hospital ward within The Hull and East 
Yorkshire Hospitals Trust (HEYHT) sites of Castle Hill Hospital and Hull Royal 
Infirmary.  Patients will be identified in the first instance during their stay on the ICU at 
either Castle Hill Hospital or Hull Royal Infirmary by senior physiotherapists 
responsible for the delivery of respiratory and rehabilitation services to this group. Any 
patients with a known period of intubation and ventilation lasting in excess of 48 hours 
will be highlighted as a potential participant to senior physiotherapists working on the 
wards where patients will be transferred to.   

                    
 
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Potential participants will be approached for the first time near the end of their hospital 
stay by a senior physiotherapist from the direct care team looking after them, who will 
briefly explain the study intentions. For those deemed to fulfil the inclusion criteria and 
none of the exclusion criteria, an information sheet will be offered to the potential 
participant to read and discuss study participation possibly with their family and friends. 
There is a significant risk that patients may be discharged home if there is too much 
time between the initial approach and undertaking the activities. With this in mind, 24 
hours only will be permitted for participants to express interest in involvement to the 
senior physiotherapist who supplied the study information or a physiotherapist directly 
involved in their care.  
Patients who express interest in the study will be communicated to the CI by the senior 
physiotherapists directly involved in their care. The CI will only approach patients who 
have expressed verbally to the ward physiotherapy staff that they would like to meet 
with her to discuss potential involvement.  The CI will arrange to meet the patient at 
their earliest convenience (which may be the same day), to discuss the study in more 
detail, providing an overview of what is required for participation and the format of the 
informed consent process. She will answer any further questions they may have 
following reading the information sheets.  It will be made explicit that if they do not 
wish to participate in the study this will not affect their treatment in any way and they 
will be thanked for the interest already shown in the study.  Informed consent will be 
collected at this meeting via a separate consent form, should the patient express a wish 
to participate. The CI will also sign the form as the ‘person obtaining consent’ at this 
meeting. The participant must be physically able to sign the consent form themselves 
prior to taking part in the study. This form will be retained by the CI, with a further 
duplicate copy given to the participant. A copy will also be placed in the medical notes 
of the participant. Together with the patient information sheet.  
Once informed consent has been gained data collection will commence within 24 hours. 
Prior to undertaking data collection, the CI will ascertain that each participant is still 
physically able to undertake the movement protocol and has not suffered any 
deterioration in their condition. They will be asked for a final time if they still wish to 
participate and if so, data collection will begin.    
 
 

                    
 
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Study procedure 
Body mass index (BMI) will be calculated by using the latest weight recording (in 
kilogrammes) on the participants observation charts and asking participants to estimate 
their height, which will be converted to centimetres if given in feet and inches. 
Participants will wear two Actigraph GT3X accelerometers, one anteromedially around 
the mid - thigh and the other around the ankle of the same (ipsilateral) leg resting above 
the lateral malleolus. The CI will attach the accelerometers, ensuring they feel 
comfortable and pose no circulatory concerns. The placement sites will be checked on a 
half hourly basis during the data collection period. This has been recommended by the 
tissue viability team, to ensure the accelerometers are not compromising skin integrity 
or circulation. A standardised assessment form will be used for this process, which has 
been constructed with assistance from the tissue viability team. 
The data collection period will not exceed three hours; including rest periods. 
Accelerometers will be removed at any time during the data collection period should a 
participant request this. Any data that has been collected during the time period that the 
accelerometers were worn prior to the request for removal will be downloaded and 
included within the analysis with the participant’s permission.  
Participants will be free to undertake the activities within the semi-structured movement 
protocol in any order they prefer. Whilst undertaking the movements, participants will 
be observed by the CI. Although there is a requirement for the CI to be able to visualise 
them, the actual distance that she is from the patient will be determined according to the 
individual’s wishes. Respect for privacy and dignity will be of paramount importance. 
Participants will not be observed if they are using a commode, the toilet or if bathing. 
The accelerometer data downloaded during these periods of time will be excluded from 
data analysis. A digital clock with an hour, minute and second display, successfully 
employed within the feasibility study will be used to note the time (to the hour, minute 
and second) when a particular movement or postural change occurred and ended. Once 
a postural change ends, a further five seconds will be observed on the digital clock 
before the new body position is documented as complete. This is to accommodate 
findings from the feasibility study and subsequent manufacturers recommendations 
related to how the accelerometer models process information.  The digital clock will be 
synchronised to the time setting on a laptop computer, which will also be used to 
activate the desired settings on both accelerometers (termed ‘initialisation’). These 

                    
 
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processes will occur immediately before the data collection period to maximise 
synchronisation of the digital clock with the time setting on the accelerometers. The 
laptop computer will not be used during data collection, only for time synchronising the 
digital clock and for initialising the settings onto both accelerometers. The 
accelerometers will be programmed to capture data every second (one second epoch).  
Following completion of the data collection period, the information captured by the 
accelerometers will be downloaded as soon as possible onto the laptop computer.  The 
time when a movement commenced and ceased (with the addition of five seconds to 
accommodate accelerometer processing), will be noted by the CI. The type of 
movement and body positions adopted will also be documented (lying, sitting or 
standing).  If the movement involves walking, the CI will count the number of steps 
undertaken manually, entering all of the above information onto a data collection sheet. 
The participant will not miss any refreshments, food or any investigations and they will 
also be encouraged to undertake usual daily activities, e.g. reading a paper or watching 
the television. If the participant requests some time alone, in the case of making a phone 
call for example, the CI will comply, but encourage the participant to remain in the 
same body position. If they were sitting in a chair for example, they would be 
encouraged to remain seated, agreeing a time for the CI to return (e.g. fifteen minutes).   
Should any procedures or personal cares be necessary, the CI will respect the need for 
privacy and dignity and leave until they are complete. The data captured by the 
accelerometers during these time periods will be excluded from data analysis, as there 
will be no criterion measure (observation) to compare accelerometer data against.  
Observational data will be collected by the CI using a data collection form specifically 
designed for this purpose, which will be entered into an electronic format within the 
IBM SPSS statistics programme (version 20) for data analysis. The CI will undertake all 
data collection procedures and undertake statistical analysis.  
Upon completion of the period of observation the accelerometers will be removed and 
the skin examined for one final time. Participants will be asked to rate their views on 
acceptability of wearing the accelerometers at the two placement sites. They will be 
asked to consider the question in relation to the individual placement sites and in 
combination. One question will be asked: 
1. How would you rate the comfort of wearing the accelerometers? 

                    
 
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Participants will be requested to match their answer to a statement on a five-point Likert 
Scale which will be printed on a sheet for them: 
1. Very uncomfortable 
2. Somewhat uncomfortable 
3. Neither comfortable or 
uncomfortable 
4. Somewhat comfortable 
5. Very comfortable 
 
A similar method of gaining feedback from participants regarding accelerometer 
comfort has been used in previous studies (Kramer et al., 2013).   
Participants will also be asked if they have any comments they wish to make regarding 
the accelerometers, which will be noted as free text should any be forthcoming.  
Study format  
Potential participant 
approached by ward 
physiotherapist to deliver 
verbal/ written information 
on the study 
 
 
 
 
 
 
 
 
 
Potential participant declines 
participation 
Interest expressed in 
participation 
CI contacted who visits the 
potential participant to deliver 
further details and collect written 
informed consent should they 
wish to participate 
Potential participant 
declines involvement 
Involvement with the study 
complete 
Involvement with the study 
complete 
Consent obtained 
Data collection  
Participant involvement 
complete 
24 hours 
Max. 24 hours 
24 hours 

                    
 
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Semi structured movement protocol 
1. Lying in bed with the legs straight and the bed head set at a comfortable height 
as dictated by the participant 
2. Lying on the left side 
3. Lying on the right side 
4. Moving from lying to sitting over the side of the bed  
5. Sitting to standing 
6. Sitting in a chair 
7. Mobilising a distance determined by the functional ability of the individual 
participant at that point in their recovery. 
N.B. The participant will be free to undertake these movements in any order they wish, 
but there is a requirement to undertake as many of these movements as possible within 
the observation period, which will not exceed three hours. The participant will be 
provided with a sheet to remind them of the movements required to be undertaken. This 
will contain a tick box so they can mark off when a particular movement was 
completed. If a movement is missed, the CI will encourage the participant towards the 
end of the observation period to undertake it.  
Infection control considerations 
Advice has been sought from the HEYHT Infection Control Team regarding infection 
control considerations when using the accelerometers with patients’ resident within 
HEYHT. The recommendations are as follows: 
1. Elastics belts must be single patient use only and fastened using Velcro 
2. The part of the accelerometer that permits download to the computer should be 
covered with a piece of easily removable tape (e.g. ‘Scotchtape’) to permit the 
whole device to be swabbed down with a Tristel wipe following the three-hour 
period of data collection per participant.   
3. The devices are not required to be placed in a nylon pouch prior to application.  
 

                    
 
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Tissue viability considerations 
Advice has been sought from the HEYHT Tissue Viability Team during construction of 
this methodological protocol. The inclusion and exclusion criteria have been 
constructed in such a way to consider those populations where placement of the 
accelerometers may pose additional and unnecessary risk. An assessment form has been 
constructed with advice from the same team to use when undertaking the half hourly 
assessment of skin integrity and circulation of participants during the data collection 
period.     The Tissue viability team borrowed the accelerometers to assess whether they 
posed any significant risk to tissue viability and to assist in construction of the 
eligibility criteria for participation.  
Data collection process 
A data collection sheet will be populated during the data collection period.  Rest periods 
and the positions participants adopt (e.g. lying, sitting or standing) will be recorded also.  
Accelerometer data will be captured using the three different measurement modes 
available on the GT3X devices. Activity intensity detection is a default setting on the 
devices. These modes can be initialised onto the accelerometers simultaneously for 
eventual download onto the computer. A password protected laptop computer will be 
used for the initialisation of the accelerometers and subsequent data download. This 
laptop computer has direct remote access to the CI’s personal folders on the York St 
John University (YSJU) virtual desktop facility, which is secure and password 
protected. Data files can be transferred electronically to the YSJU student virtual 
desktop to permit statistical analysis within SPSS.   
The accelerometer settings (measurement modes) will be: 
 Physical activity count (a default setting), giving a numerical score related to 
intensity of activity, the greater the count, the greater the acceleration of movement, 
hence the greater intensity  
 Step count   
 Inclinometer for identification of  body position (lying, sitting or standing)  
 

                    
 
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There are only four readings the inclinometer setting on this particular device can 
supply, which are detailed below: 
0 = Device is off (not being worn by patient) 
1 = standing 
2 = lying horizontally 
3 = sitting upright   
Sample size calculation 
A sample size of 20 participants will be recruited. This sample size has been used in 
previous research investigating the validity of a different accelerometer model to 
quantify gait parameters in patients recovering from critical illness (Edbrooke et al., 
2012). They predicted that 12 subjects were necessary based upon alpha = 0.05 
(significance level), beta = 0.9 (power) and a correlation of r = 0.75, categorised as a 
good to excellent correlation (Trapp and Dawson, 2004).  A sample size of 20 was also 
recruited in another study investigating the validity of accelerometer measurement 
within a hospitalised stroke population (Kramer et al., 2013).  Recruiting a sample of 20 
patients will permit some attrition should there be any accelerometer malfunction or 
decisions to withdraw, yet supply an achievable number for participant recruitment 
based on feedback from clinical colleagues working within the specialty.  
Statistical analysis 
IBM SPSS statistics (Version 20) will be used to undertake statistical analysis. Some 
data captured by the accelerometers is continuous and others categorical.  
Categorical data 
Categorical data, concerning body position (lying, sitting or standing) will be analysed 
using the Kappa statistic, calculating agreement between the accelerometer inclinometer 
data and direct observation. Each accelerometer placement site (thigh and ankle) will 
initially be analysed separately. Examination of the inclinometer raw data captured from 
both placement sites will determine whether an algorithm can be constructed using 
readings from both the ankle and thigh placement to improve determination of the sitting 

                    
 
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position specifically if necessary.  Direct observation will serve as the criterion measure 
for all the analyses.  
Percentage agreement of inclinometer raw data from the thigh and ankle accelerometers 
with direct observation for detection of each separate body position will be calculated. A 
further percentage agreement analysis will be undertaken if an algorithm can be 
constructed for determination of the sitting position using readings from both placement 
sites.  This algorithm will be compared against direct observational raw data identifying 
the sitting position only. This result will be compared against the percentage agreement 
of the individual placement sites in determination of the sitting position. This will assist 
in determination of whether the algorithm is more superior to a single placement site in 
determination of the sitting position.  
Continuous data 
Agreement between step count recorded by each accelerometer placement site and direct 
observation (manual counts) as a criterion measure will be determined using Bland 
Altman analysis with 95% limits of agreement (LOA).  
 Acceptance of the devices over a three-hour period 
The statements within the Likert scale will be collapsed to obtain trues positives (very 
comfortable and somewhat comfortable) and true negatives (very uncomfortable and 
somewhat uncomfortable). The middle category (neither comfortable nor uncomfortable) 
will remain a separate category. A descriptive analysis will be undertaken to investigate 
this particular aspect of enquiry using percentages of true positives, the middle category 
and true negatives.   This will be presented graphically. 
Any specific comments made by the patients in relation to acceptability of the devices 
will be included as free text within the results section. The statements will be anonymous 
and permission from participants will be sought regarding their inclusion within the body 
of the thesis or publications which may arise from it.     
 

                    
 
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Ethics approval 
This study has received approval from the NHS Local Research Ethics Committee 
(REF: XXXXX) and the Research Ethics Sub Committee, YSJU (REF: XXXXXX).  
Data handling and confidentiality  
All participants will be assigned a unique reference number which will be linked to 
personal details stored securely on paper. Any electronic data will be anonymous, 
bearing the unique reference number of the participant and their initials only, with no 
personally identifiable information included within the data files. Only the CI will have 
the ability access to trace data files created from accelerometry measurements to the 
individual participant, using their unique reference number and initials within the file 
name.  
Any paper documentation, which may include personal data (e.g. signed consent form, 
personal contact details), will be kept in a locked filing cabinet within the Therapies 
Centre, Hull Royal Infirmary. This is shared with one other colleague, Dr. Angela 
Green, who is also a member of the PhD supervision team.  This office is always locked 
when vacant. Preferred personal contact details will only be obtained at the consent 
phase should the participants express a desire to hear of the results.  
The CI will adhere to the NHS Information Governance (IG) Toolkit Regulations, 
professional codes of conduct and relevant HEYHT and YSJU policies and procedures 
at all times. No information regarding research participants will be passed to third 
parties not directly involved in the research.  
The identity of individual participants in the research report and any publications will 
remain confidential and anonymous. Data protection will conform to the Data 
Protection Act 1998.   
Finance  
This study has not received any funding from external sponsors and all accelerometry 
equipment and software has been supplied by YSJU. Lack of an ability to employ 
language interpreters, due to no external funding has necessitated the requirement to 
enrol only those who have a good command of the English language.   

                    
 
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Reporting and dissemination 
This study will form part of a PhD thesis, investigating the validity of a particular 
model of accelerometer (the Actigraph GT3X) for use as a clinical measurement tool to 
quantify the typical activities patients undertake on a hospital ward as they continue 
their recovery following critical illness.   
Following data analysis, opportunities will be sought for presentation of results at 
National Conferences, including the University College London (UCL) annual 
conference ‘Critical Care Update for Physiotherapists’. Abstracts are hoped to be 
submitted for peer review to other relevant National Conferences, including 
Physiotherapy UK for oral presentation/ poster presentation.  
Opportunities for poster presentations, hospital service improvement conferences, 
YSJU or University of Leeds (UoL) conferences will also be sought. Presentation 
within the research seminar programme held within the Health and Life Sciences 
Faculty (HLS) at YSJU will also be explored, following guidance and consultation with 
the PhD supervision team.  
Presentations via local research networks and critical care networks will be explored, 
together with a submission to a selected journal for peer review to consider for 
publication.    

                    
 
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