Can Sit-to-walk Assessment Maximize Instrumented Timed Up & Go

Test Output?

Slavka Viteckova

, Radim Krupicka

, Petr Dusek

, Patrik Kutilek

Zoltan Szabo

and Ev

zen R

cka

Faculty of Biomedical Engineering, Czech Technical University in Prague, Kladno, Czech Republic

Department of Neurology and Centre of Clinical Neuroscience, First Faculty of Medicine and General University Hospital

in Prague, Charles University in Prague, Prague, Czech Republic

Keywords:

iTUG, Angular Rate, Sit-to-Stand, Transition, Movement.

Abstract:

Daily human activities commonly include standing from a seated position. In research this transition is inves-

tigated, among others, as a part of a functional Timed Up & Go test. Spatio-temporal parameters are widely

used to assess the sit-to-walk transition. Usually, the parameters calculated for the sit-to-walk signal is in

its entirety. Another approach primarily splits the transition into phases and then calculates parameters for

individual phases separately. The objective of this work is to examine whether splitting the Timed Up & Go

test into subphases provides additional value for transition assessment. In order to compare both approaches,

we utilized angular rate parameters (duration, peak value, mean, variance) and analyzed their reliability. The

reliability proved to be dependent on the subject group and transition phase. In addition, we compared tran-

sition parameters from the entire transition and individual phases between the two subject groups. The mean

only differentiated between the subject groups in individual phases, but not is entire transition. To summarize,

splitting the transition into phases turned out to be beneﬁcial for sit-to-walk transition assessment.

1 INTRODUCTION

Standing from a seated position is a commonly per-

formed daily activity. The sit-to-stand movement is a

part of functional tests such as Timed Up & Go test.

The Timed Up & Go (TUG) test is a modiﬁed timed

version of the ”Get-Up and Go” Test (Mathias et al.,

1986). TUG involves rising from a chair, walking 3

m, turning 180

◦

, walking back to the chair, and sitting

down again. Usually, a TUG is measured as the total

time it takes to perform the test.

The increasing utilization of inertial measurement

units during the last decade increases the ability to

separate individual TUG subcomponents (Salarian

et al., 2010; Greene et al., 2010; Zakaria et al., 2015;

Smith et al., 2016; Craig et al., 2017; Newman et al.,

2018), i.e. sit-to-walk, walking forward, 180 degree

turn, walking back to the chair and turn-to-sit, and

consequently their individual assessment.

Recent studies employed two approaches to the

sit-to-walk (StW) assessment. The ﬁrst approach ana-

lyzed the entire StW at once. Salarian et al. (Salarian

et al., 2010) tested four StW parameters (duration,

peak angular velocity, mean angular velocity, and the

range of trunk movement) in Parkinson disease pa-

tients and older adults. They did not reveal any differ-

ence between the tested subject groups. Also, Weiss

et al. (Weiss et al., 2013) did not observe a differ-

ence in the transition measures (duration, accelera-

tion amplitude range, median and standard deviation)

of PD patients and older adult groups. Gal

an et al.

(Gal

an-Mercant and Cuesta-Vargas, 2014) showed a

difference in duration and acceleration-based param-

eters (minimal, maximal, and mean value) between

frail and non-frail older adults. The second approach,

Zakaria et al. (Zakaria et al., 2015) modiﬁed the StW

assessment so that they divided the transition into two

phases: sit-bend and bend-stand. Then, they assessed

the duration, acceleration and angular rate measures

(peak values, RMS) in elderly subjects with low and

high risk of falls. No differences were observed in the

transition phase measures for both groups. Although

a number of studies utilized the instrumented TUG,

only a few of them included StW assessment (Salarian

et al., 2010; Weiss et al., 2013; Zakaria et al., 2015;

Gal

an-Mercant and Cuesta-Vargas, 2014). Moreover,

Millor et al. (Millor et al., 2014) noted that the angu-

lar kinematics of StW transitions in the TUG test did

Viteckova, S., Krupicka, R., Dusek, P., Kutilek, P., Szabo, Z. and R ˚uži

cka, E.

Can Sit-to-walk Assessment Maximize Instrumented Timed Up Go Test Output?.

DOI: 10.5220/0007523902090213

In Proceedings of the 12th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2019), pages 209-213

ISBN: 978-989-758-353-7

209

not yield meaningful information. None of the pre-

vious studies assessed or compared both approaches,

i.e. the assessment of the entire StW and individual

phases at the same time.

Reliable outcomes are crucial for the interpreta-

tion of results and the subsequent adoption in clinical

practice (Smith et al., 2016). Salarian et al. (Salarian

et al., 2010) examined a TUG inter-session reliability

including the sit-to-walk transition of elderly subjects

and patients with Parkinson’s disease (PD). Their

work did not provide reliability per subject groups,

rather the analysed reliability of the mixed group. The

results showed the poor reliability of all analysed pa-

rameters (ICC<0.5). Newman et al. (Newman et al.,

2018) also assessed the intra-session reliability of a

TUG including the StW transition among children

with traumatic brain injury and controls. Although

the reliability of the sit-to-walk parameters was as-

sessed previously none of the previous works studied

the reliability of the sit-to-walk transition with a focus

on its phases.

The aim of this study is to analyse the division of

the StW transition into two phases. Speciﬁcally, to

examine the additional value of splitting the transi-

tion into subphases when compared to the transition

assessment at once. For this purpose, we compared

parameters computed for an entire StW transition and

its individual phases. Then, we assessed the reliabil-

ity of all computed parameters and compared the dis-

tinctiveness between the two subject groups, namely

older adults and Parkinson disease patients.

2 METHODS

2.1 Participants and Protocol

Two groups of participants were enrolled in this study.

The ﬁrst group included 35 early untreated Parkinson

disease (PD) patients (24 males, 11 females), mean

age 58.6 (+-13.4). The second group, control group

(CG), included 36 volunteers (32 males, 4 females),

mean age 64.3 (+-9.5). All PD patients and CG were

evaluated twice within one session (TUG

, TUG

All subjects accomplished an extended Timed Up &

Go Test (ETUG) (Wall et al., 2000). Each subject

was measured while she/he rose from a chair during

the ETUG, walked 10 meters, turned, walked back,

and sat down again. The study was approved by the

Ethics Committee of the General University Hospital

in Prague, Czech Republic, and therefore performed

in accordance with the ethical standards established

in the 1964 Declaration of Helsinki.

Figure 1: Plot showing pitch angular rate of one subject.

Bold - sit-to-walk phase of TUG.

2.2 Data Acquisition and Processing

Xbus Master (Xsens Technologies B.V.), a

lightweight (330g) and portable device using MTx

units for orientation and acceleration measurements

of body segments, was used for the measurement of

3-D orientation and 3-D acceleration. Kinematic data

was recorded from 5 gyro-accelerometers with a data

sampling rate of 100 Hz. Units were symmetrically

attached to the lateral shank of each lower leg, 4 cm

above the ankle joint, and the chest, 2 cm below the

sternal notch.

Before further processing, the raw angular rate

signal was low-pass ﬁltered with a zero-phase second-

order Butterworth ﬁlter with a 20 Hz corner fre-

quency. In this study, we focused on the sit-to-walk

(StW) transition.

In accordance with previous studies, the chest an-

gular rate sensor was used for further processing and

computation of the StW parameters. It was showed

that the TUG sit-to-walk transition can be detected as

the movement with an pitch angular rate higher than

10 deg/s (Higashi et al., 2008). As a negative angular

rate indicates a clockwise rotation, the beginning of

the StW, i.e. the beginning of the sit-bend phase, was

detected from the pitch angular rate as a value less

than -10 deg/s. As the crossing of the angular rate sig-

nal to zero means a rotation or direction change, the

end of sit-bend phase, i.e. beginning of bend-stand

phase, was detected as the crossing of the angular rate

to the value zero (Figure 1). Finally, the end of StW,

i.e. end of bend-stand phase, was identiﬁed as a value

lower than 10 deg/s (Higashi et al., 2008).

To assess the StW we employed the mean, peak

value, duration, and variance of pitch angular rate sig-

nal. All parameters were calculated for both phases

and the entire transition. Thus, we calculated 12 pa-

rameters in total.

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210

2.3 Statistical Analysis

Statistical analyses were performed to examine the re-

liability of the StW parameters. The Intra-Class Cor-

relation (ICC) between two measurements was used.

Absolute agreement was reported. According to Mc-

Graw et al. (McGraw and Wong, 1996) reliability

greater than 0.90 is considered as excellent, reliability

greater than 0.75 is considered as good, greater than

0.50 is moderate, and lower than 0.50 is poor.

Next, the hypotheses on whether the StW parame-

ters of both sit-to-walk phases are able to distinguish

a healthy subject from a PD patient was tested. The

Shapiro-Wilk test was used to verify the normality of

parameters in each observed dataset. The assumption

of a normal data distribution in the observed datasets

had been rejected (signiﬁcance level p=0.05). There-

fore, the nonparametric Wilcoxon rank sum test was

used to compare statistical signiﬁcance differences

in the sit-to-walk transition between PD patients and

control group data. The signiﬁcance level was set to

p<0.05. All preprocessing and analyses were carried

out ofﬂine using the MatLab (MatLab R2015, Math-

works, Inc., Natick, MA, USA) programming envi-

ronment.

3 RESULTS

From Table 1, it can be seen that out of the four pa-

rameters, three parameters in the control group and

one parameter in PD patients demonstrated poor re-

liability (ICC<0.50) in all three cases (entire StW,

sit-bend, bend-stand). For the control group these

were: duration, mean and variance. For PD pa-

tients this was only for duration. The peak value in

the control group showed a higher reliability (moder-

ate, ICC>0.50) in the bend-stand phase then in other

cases (poor, ICC<0.50). The mean and variance in

PD had poor reliability in the sit-bend phase and mod-

erate (ICC>0.50) in the entire StW and bend-stand.

When comparing PD patients and the control

group, the peak value, and variance were signiﬁ-

cantly different in the entire StW, sit-bend and bend-

stand phases. The mean value showed the difference

between the groups in the sit-bend and bend-stand

phases (Figure 2). The duration did not show a differ-

ence in any of the tested cases. A signiﬁcant differ-

ence in the entire StW but not sit-bend or bend-stand

phases was not observed for any of utilized parame-

ters.

4 DISCUSSION

In this work, we compared the results of the entire sit-

to-walk transition to a more detailed approach with

transition phases. We evaluated StW transition. Addi-

tionally, we divided the sit-to-walk transition into two

phases, namely sit-bend and bend-stand, and evalu-

ated them separately.

First, we analysed whether the StW measures cal-

culated per phase have similar reliability as measures

calculated for entire StW. The analyses were provided

per subject group. Based of poor reliability results

(Table 1) it can be inferred that the parameter dura-

tion of the entire StW and its phases is not suitable for

StW assessment (the entirety or its parts). The results

showed a higher reliability in PD patients than the CG

for almost for all parameters and tested cases. This

can be elucidated by the reduced concentration of the

CG to perform a StW. In the PD group, some param-

eters (mean, variance) exhibited a lower reliability in

the sit-bend phase than in other phases. In contrast

to the peak parameter, mean and variance are affected

by the accuracy of StW detection. Especially the de-

tection of the StW beginning is a challenging task be-

cause the sit-bend phase may be preceded by gently

bending forward and backward. Thus, a comparison

of detection methods with respect to their impact to

StW parameters is needed to make results more com-

parable across studies.

In addition, the training effect might play impor-

tant role in reliability assessment of two consecutive

trials. To our knowledge, the training effect of TUG

subcomponents has not yet been studied.

Second, we tested whether StW phases can dif-

ferentiate between PD patients and older adults bet-

ter than entire StW. The present study is consistent

with previous works. No differences between PD a

CG were observed for duration and mean parameters

computed for entire StW (Salarian et al., 2010; Weiss

et al., 2013). Unlike duration, the mean parameter re-

vealed a difference between these groups in both indi-

vidual phases (sit-bend, bend-stand). Finally, we sug-

gest that splitting StW into phases can beneﬁt a TUG

StW analysis.

Nevertheless, there are some limitations to this re-

search study. The most important is that the sam-

ple size of the subjects was not high. However, 71

subjects proved to be sufﬁcient for preliminary re-

search which managed to test the basic attributes of

the method proposed for further studies of TUG.

Can Sit-to-walk Assessment Maximize Instrumented Timed Up Go Test Output?

211

Table 1: Intra-class correlation and Wilcoxon rank sum test outcomes for the two TUG measurements. TUG

-ﬁrst TUG mea-

surement, TUG

-second TUG measurement, Var.-variance,

∗

-statistically signiﬁcant difference,



-moderate or good intraclass

correlation.

Entire StW Sit-bend phase Bend-stand phase

ICC PD vs CG ICC PD vs CG ICC PD vs CG

(p-value) (p-value) (p-value)

CG PD TUG

TUG

CG PD TUG

TUG

CG PD TUG

TUG

Time 0.12 0.40 0.06 0.38 0.17 0.48 0.06 0.42 0.09 0.33 0.14 0.16

Peak 0.42 0.73



<0.01

∗

<0.01

∗

0.43 0.74



<0.01

∗

<0.01

∗

0.53



0.74



<0.01

∗

0.09

Mean 0.30 0.72



0.80 0.49 0.19 0.39 <0.01

∗

0.04

∗

0.44 0.53



<0.01

∗

0.04

∗

Var. 0.40 0.53



<0.01

∗

<0.01

∗

0.43 0.31 0.01

∗

<0.01

∗

0.37 0.70



0.03

∗

0.02

∗

Figure 2: Scatter plots showing mean pitch angular rate differences between PD patients and control group (CG) in the entire

StW, sit-bend and bend-stand phases. The top scatter plot represents the ﬁrst TUG measurement (TUG

) and the bottom

represents the second TUG measurement (TUG

5 CONCLUSIONS

This paper tested and compared two approaches to

Timed Up & Go sit-to-walk transition analysis: the

analysis of the entire transition at once and the anal-

ysis per phases. The reliability of sit-to-walk param-

eters was tested as well as the ability to differentiate

between subject groups. We can designate that the

transition splitting into phases can provide new in-

sight into sit-to-walk transition assessment.

ACKNOWLEDGEMENTS

This work has been supported by the Czech science

foundation, grant No. 16- 07879S “REM sleep be-

havior disorder: predicting the risk of neurodegener-

ation” and Ministry of Health of the Czech Repub-

lic, AZV Grant no. 16- 28119a ”Analysis of move-

ment disorders for the study of extrapyramidal dis-

eases mechanism using motion capture camera sys-

tems”.

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212

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