Shinshu Med J, 61⑵ :57〜64, 2013

Comparison of Distance of 6‑min Walk Test and the Incremental Shuttle
Walk Test with Lung Function or Quality of Life in Patientswith Chronic Obstructive Pulmonary Disease
Atsuhito USHIKI , Keisaku FUJIMOTO ＊, M ichiko ITO , Masanori YASUO
Kazuhisa URUSHIHATA , Masayuki HANAOKA and Keishi KUBO
1) First Department of Internal Medicine, Shinshu University School of Medicine
2) Department of Clinical Laboratory Sciences, Shinshu University School of Health Sciences
3) Endoscopic Examination Center, Shinshu University School of Medicine

Background :Field walk tests such as the 6‑min walk test (6MWT) and the incremental shuttle walk test
(ISWT)are simple tests for assessing the degree of disabilityin individuals with chronic obstructive pulmonary
disease(COPD).Inthepresent study,thecorrelation between exerciseperformanceand lung function or health‑related quality of life (HRQoL)in both the 6M WT and the ISWT was examined in COPD patients.
Methods:A retrospective examination of 105 patients with COPD using the 6M WT or the ISWT and bothlung function tests and assessment of HRQoL with the St Georgeʼs Respiratory Questionnaire (SGRQ) was
performed,and the correlation between walking distance and lung function parameters or SGRQ scores wereassessed in each test.
Results:Walking distance was not correlated with lung function parameters,but was signiﬁcantly correlatedwith the activity and impact domains, as well as the total score of the SGRQ in the 6M WT. In the ISWT,
walking distancecorrelatedsigniﬁcantlywithinspiratorycapacity,forced vitalcapacity,and forced expiratory
volume in one second, but not with the total score of the SGRQ.
Conclusion : The 6MWT is reﬂective of health‑related quality of life and the ISWT is reﬂective of lungfunction. Shinshu Med J 61 : 57 ―64, 2013
(Received for publication October 29, 2012;accepted in revised form December 13, 2012)
Key words:chronic obstructive pulmonary disease, 6‑min walk test, incremental shuttle walk test,
St Georgeʼs Respiratory Questionnaire

Introductionof functional exercise capacity.Of these modalities,
ﬁeld walk tests require less technical expertise andExercise testing is useful for the assessment ofequipment, are simple to perform and are inexpen-

the degree of disability, prognosis for survival,

sive . Field walk tests are therefore extensively

presence of exercise‑induced hypoxemia, andused for clinical or research purposes. A variety of

response to treatment in patients with chronic

walk tests exist, including time‑based tests, ﬁxed‑

obstructive pulmonary disease (COPD) . Several

distance tests, and controlled‑pacing tests.

modalities are available for the objective evaluation

The 6‑min walk test (6MWT)is currentlythe testof choice as a functional walk test for clinical or

Corresponding author:Keisaku Fujimoto
Department of Clinical Laboratory Sciences, Shinshu
University School of Health Sciences, 3‑1‑1 Asahi,
Matsumoto, Nagano 390‑8621 JapanE‑mail:fkeisaku＠shinshu‑u.ac.jp

No. 2, 2013

research purposes . However the 6 min walking
distance depends on the motivation of the patient
because the 6M WT is a self‑paced test.
The incremental shuttle walk test (ISWT) is a57

Ushiki.Fujimoto.Ito et al.

submaximal exercise test based on incremental

2006)or the ISWT group (from 2007 to 2008). This

increase in walking pace . Consequently, maximal

study was approved by the institutional research

exercise capacity is probably better correlated withethics committee of Shinshu University School of

the ISWT than with the 6M WT. The ISWT is a

M edicine and informed consent was obtained from

reproducible measure of functional capacity ineach patient.

patients with chronic airﬂow limitation, and strong

Lung function tests

correlations between ISWT distance and maximal

Spirometry, lung volume, and diﬀusion capacity

oxygen consumption have been reported, measured

for carbon monoxide (DLCO)were measured using

during treadmill testing .

Chestac‑8800 (Chest Co. Ltd, Tokyo, Japan) in

Whether the walking distance in the 6MWT or

accordance with the American Thoracic Societythat in the ISWT shows a better correlation with

protocol . Functional residual capacity (FRC) was

lung function or health‑related quality of life

measured using a gas‑dilution method, after which(HRQoL) is still unclear, although both walking

the subject immediatelyinspired to total lung capac-

tests have been used for evaluation of exercise

ity (TLC) and expired maximally to residual vol-performance in patients with COPD. We hypothes-ume (RV), allowing calculation of lung volume andized that the 6MWT is more reﬂective of HRQoL,

RV/TLC. DLCO was measured using the single‑

because the 6MWT is a self‑paced test and reﬂects

breath method. For the predicted values for forced

activity of daily life, and the ISWT better reﬂects

expiratory volume in one second (FEV ) and vitallung function because it is closer to a submaximal

capacity(VC),Japanese local reference data devel-

exercise test.In the present study,we examined theoped by the Japanese Respiratory Society were

results of ﬁeld walk tests (6MWT or ISWT), lung

adopted, and the predicted values for DLCO andfunction tests,and HRQoL using St Georgeʼs Respi-lung volumes (FRC, RV, and TLC) measured byratory Questionnaire (SGRQ), and analyzed the

body plethysmography were determined using thewalking distance in each walking test in correlation

formulas of Nishida et al. and Koryet al. ,respec-with lung function parameters and SGRQ scores intively.

patients with stable COPD.
Subjects and Methods
Subjects

Health‑related quality of life
HRQoL was assessed using a Japanese version of
the SGRQ,which consists of 76 items and calculatesa 3‑component score (symptoms, activity, andThis study was a retrospective study. One hun-

impact)and a total score.The symptom component

dred and ﬁve consecutive symptomatic patientscontains items related to symptomatology, includ-with stable COPD who had been seen at the out-

ing frequency of cough, sputum production, wheez-patient clinic of Shinshu University Hospital froming, and breathlessness. The activity component is2005 to 2008 were recruited and the results of ﬁeld

concerned with physical activities that either cause

walk tests, lung function tests, and HRQoL using

or are limited bybreathlessness.The impact compo-

SGRQ were examined concurrently. COPD wasnent covers such factors as employment, being in

diagnosed in accordance with the Global Initiative

control of health, panic, medication needs and sidefor Chronic Obstructive Lung Disease guidelines .

eﬀects, and disturbance of daily life. Each of these

Patients with a history of long‑term oxygen ther-scores ranges from 0 to 100, with a score of 100

apy, respiratory tract infection or exacerbation

indicating maximum disability . The Japanese

during the preceding 3 months, and ischemic heart

version of SGRQ is a valid and reliable measure ofdisease or locomotive problems were excluded.

impaired health in COPD .

Patients were divided into 2 groups according to theexamination date:the 6MWT group (from 2005 to
58

Field walk test
１ The 6MWT
Shinshu Med J Vol.61

Field walk test in COPD

The 6MWT was performed according to thecompared using Fisherʼs exact test.Simple correla-

American Thoracic Society Guidelines . In sum-

tions between various parameters were examined

mary, the patients were instructed to walk at theirusing Pearsonʼ
s correlation coeﬃcient. A Pearson

fastest pace, attempting to cover the maximum

correlation coeﬃcient of 0.40 or above was consid-

possible distance within 6 min. Percutaneous oxy-ered satisfactory. M ultiple stepwise linear regres-gen saturation (SpO ) and pulse rate (PR) weresion analysis was performed to identify which vari-continuously monitored. An investigator timed theables were signiﬁcant determinants for the walking

walk, and used the standard phrases of encourage-

distance or HRQoL. A value of p≦0.15 was used

ment. The patients were allowed to stop anytime

ﬁrst to identify candidate variables, and then vari-

and anywhere until they had suﬃciently rested toables were removed from the regression model if

start walking again.Before and after the test,SpO ,the p value was more than 0.1. All statistical ana-

PR,and blood pressure were measured,and dyspnea

lyses were performed using a Windows‑compatible

was rated using the modiﬁed Borg breathlessness

software program (Stat Flex ver. 5.0, Artech Ltd.,

scale (BS).

Osaka, Japan). A p value of＜0.05 was considered

２ The ISWT

statistically signiﬁcant.

The ISWT was performed according to a previ-

Results

ously reported method . In summary, the patient
walked up and down a 10‑m course. The speed at

Patient details

which the patient walked was dictated by an audio

Patient characteristics and lung function values

signal played on a compact disc.This compact discare shown in Table 1. Among the 105 patients, 52

emitted a single bleep at regular intervals,at which

patients (5 female patients)were classiﬁed into thepoint the subject attempted to reach the opposite

6M WT group, and 53 patients (3 female patients)

end of the course. Walking speed was increased

into the ISWT group. There were no signiﬁcant

every minute by a small increment, which meantdiﬀerences in patient characteristics between the 2that the patient was required to walk at a progres-groups, except for the mean inspiratory capacity

sively faster pace. The end of the test was deter-(IC)/TLC and DLCO,which were signiﬁcantlylower

mined byeither (a)the patient,when the patient wasin the 6M WT group than in the ISWT group, andtoo breathless to maintain the required speed,or (b)the mean, which was signiﬁcantly higher in thethe investigator, if the patient failed to complete a

6M WT group than in the ISWT group. The mean

shuttle in the time allowed. SpO and PR were

SGRQ symptom score,activity score,impact score,continuously monitored. Before and after the test,

and total score in the 6MWT

SpO ,PR,respiration rate,and blood pressure weresigniﬁcantly higher than in the ISWT group (Table

measured,and dyspnea was rated using the modiﬁed2).The results of the walk tests are shown in Table

BS.

3. The mean post‑SpO , delta SpO , and the mean
Statistical analysis

group werepre‑ and post‑modiﬁed BS did not signiﬁcantly

All results were expressed as mean±SD. Datadiﬀer between the 2 groups. The mean pre‑SpO ,distributions of variables in the various groups werepost‑PR, and delta PR in the ISWT group wereﬁrst assessed using the goodness‑of‑ﬁt test. Whensigniﬁcantly higher than in the 6M WT group. The

data for variables showed a normal distribution,themean pre‑PR in the 6MWT group was signiﬁcantly

2 groups were compared using the unpaired t test.

higher than in the ISWT group.

When data for variables did not show a normal

The relationship between walking distance

distribution, variables between the 2 groups wereand lung function or HRQoL (Table 4)compared using the M ann‑Whitney U test. Gender

The 6M WT

distribution diﬀerence between the 2 groups was
No. 2, 2013

distance (6M WD) showed asigniﬁcant correlation with the activity and impact
59

Ushiki.Fujimoto.Ito et al.
Table 1 Patient characteristics and lung function parameters

Age (yr)
Gender (male/female)
BH (cm)BW (kg)
BMI (kg/m )VC, % of predicted (%)
FEV , % of predicted (%)
FEV /FVC (%)
IC/TLC (%)
FRC, % of predicted (%)
RV, % of predicted (%)
TLC, % of predicted (%)
RV/TLC (%)
DLCO, % of predicted (%)

6M WT group(n＝52)ISWT group(n＝53)

p value72.6±7.1
47/5
162.9 ±7.5
57.8±9.7
21.7±2.998.0±16.9
63.4±24.2
52.2±14.3
35.6±8.6
107.7±29.1
156.2±48.0
114.0±18.7
47.0±8.748.2±19.3

70.0±7.3
50/3
163.5±6.4
58.4±10.1
21.8±3.1
105.0±20.4
69.0±22.4
56.5±13.1
39.8±8.4
99.9 ±19.3
141.9 ±42.0
112.4±18.4
42.1±10.0
56.1±21.1

p＝0.065
p＝0.692
p＝0.662p＝0.753
p＝0.929p＝0.091p＝0.223
p＝0.110p＝0.012p＝0.272
p＝0.115
p＝0.684
p＝0.009
p＝0.048

Values are mean±SD
COPD :chronic obstructive pulmonary disease;6MWT :6‑min walk test ;ISWT :incremental
shuttle walk test ; BH : body height ; BW : body weight ; BMI : body mass index ; VC : vital
capacity; FEV : forced expiratory volume in one second ; FVC : forced vital capacity; IC :inspiratory capacity;TLC :total lung capacity;FRC :functional residual capacity;RV :residual
volume;DLCO:diﬀusion capacity for carbon monoxide
Table 2 SGRQ scores of patients with COPD

SGRQ symptom score
SGRQ activity score
SGRQ impact score
SGRQ total score

6M WT group(n＝52)ISWT group(n＝53)

p value

51.106±22.138
58.492±30.273
28.010±18.055
43.013±19.830

38.200±19.016
35.688±25.735
18.589 ±17.497
29.113±18.058

p＝0.002p＜0.001p＝0.005p＜0.001

Values are mean±SD
COPD :chronic obstructive pulmonary disease;6MWT :6‑min walk test ;ISWT :incremental
shuttle walk test ;SGRQ :St Georgeʼs Respiratory Questionnaire
Table 3 Summary of walk test result of patients with COPD

pre SpO (%)
post SpO (%)ΔSpO (%)
pre PR (/min)post PR (/min)
ΔPR (/min)pre modiﬁed Borg breathlessness scalepost modiﬁed Borg breathlessness scale
walk test distance (m)6M WT group(n＝52)ISWT group(n＝53)

94.9 ±1.8
86.8±8.6‑8.1±8.2
81.6±12.8
108.5±12.826.9 ±13.3
0.22±0.50
3.88±2.41387±106

95.7±1.589.4±5.6‑6.3±5.174.8±13.6
119.2±19.0
44.4±22.2
0.21±0.55
3.19 ±2.20
365±143p value
p＝0.014p＝0.262p＝0.685p＝0.007p＝0.002p＜0.001p＝0.422p＝0.082

All values represent mean±SD
Pre‑ and post‑modiﬁed Borg scales represent median and ranges.
COPD :chronic obstructive pulmonary disease;6M WT :6‑min walk test ;ISWT :incremental shuttle walktest ;SpO :Oxygen saturation ;ΔSpO :post SpO ‑pre SpO ;PR :pulse rate;ΔPR :post PR‑pre PR

60

Shinshu Med J Vol.61

Field walk test in COPD
Table 4 Simple regression analysis using Pearsonʼ
s correlation coeﬃcient
6M WT distance

ISWT distanceCoeﬃcientp valueCoeﬃcientp value

FVC

0.33

0.52

FEV
FEV /FVC
FRC
RV

0.34
0.17
0.19
0.21

p＜0.016p＜0.013p＝0.239p＝0.168
p＝0.135p＜0.001p＜0.001p＝0.011p＝0.922p＝0.124

TLC
IC
RV/TLC0.28
0.27

p＝0.044p＝0.049p＝0.860p＜0.001

0.24
0.46
‑0.35

DLCO
SGRQ symptom score
SGRQ activity score
SGRQ impact score
SGRQ total score
pre SpOdelta SpO
post modiﬁed Borg scale

0.02
0.61
‑0.28
‑0.65
‑0.63
‑0.60
0.45
‑0.26
‑0.21

p＝0.041p＜0.001p＜0.001p＜0.001p＜0.001p＝0.061p＝0.141

0.50
0.35
‑0.01
‑0.21

0.50
‑0.18
‑0.44
‑0.28
‑0.33
0.28
‑0.12
‑0.02

p＝0.888p＜0.001p＝0.009p＜0.001p＝0.190p＝0.001p＝0.044p＝0.015
p＝0.038p＝0.378p＝0.845

COPD : chronic obstructive pulmonary disease; 6MWT : 6‑min walk test ; ISWT : incremental
shuttle walk test ;FVC :forced vital capacity;FEV :forced expiratory volume in one second ;FRC :functional residual capacity;RV :residual volume;TLC :total lung capacity;IC :inspiratory capacity; DLCO : diﬀusion capacity for carbon monoxide; SGRQ : St Georgeʼs Respiratory
Questionnaire;delta SpO :diﬀerence post SpO from pre SpO

Fig. 1
The relation between St Georgeʼs Respiratory Questionnaire(SGRQ)total score and the ﬁeld walk tests.The
correlation coeﬃcient between the 6‑min walk distance (6M WD)and SGRQ total score is ‑0.60.The correlation coeﬃcient between the incremental shuttle walk test distance (ISWD)and SGRQ total score is ‑0.33.

domain scores,and the total score of SGRQ (Fig. 1)

correlated with FVC,FEV (Fig. 2),IC,and DLCO,

with a correlation coeﬃcient over 0.4. With regard

showing a high correlation coeﬃcient of over 0.4.

to lung functions,DLCO was signiﬁcantlycorrelated

However, with respect to HRQoL, weak correla-with 6M WD, showing a coeﬃcient of 0.61. The

tions between ISWD and the SGRQ scores werecorrelation coeﬃcients between 6MWD and FVC,

observed compared to the correlations between the

FEV , TLC and IC were less than 0.4.On the other

6M WD and the SGRQ scores.

hand, the ISWT distance (ISWD) was signiﬁcantly
No. 2, 2013

The regression model for the 6M WD was
61

Ushiki.Fujimoto.Ito et al.

Fig. 2
The relationship between forced expiratory volume in one second (FEV ) and the ﬁeld walk test. The
correlation coeﬃcient between the incremental shuttle walk test distance (ISWD) and FEV is 0.50. The
correlation coeﬃcient between the 6‑min walk distance (6M WD)and FEV is 0.34.

signiﬁcant (r＝0.68) and comprised DLCO (R ＝evaluated by6M WD correlated better with HRQoL,

0.376,p＜0.001),FEV (R ＝0.117,p＝0.012),and RV/

but did not show a good correlation with parame-

TLC (R ＜0.001,p＝0.014).This model accounted forters of airﬂow limitation. Multiple, stepwise, linear

42.8% of the walking distance in the 6MWT, andregression analysis also revealed that 6MWD was

DLCO was the most signiﬁcant determinant. The

the most signiﬁcant contributing factor for the

regression model for the total SGRQ score was

evaluation of HRQoL among all the lung function

signiﬁcant (r＝0.70)and included 6MWD (R ＝0.359,

parameters tested. Previous reports showed thatp＜0.001) and FEV(R ＝0.291, p＝0.001). Thismaximum heart rate and BS rating were higher atmodel accounted for 46.5% of the SGRQ, andthe end of the ISWT than at the end of the 6MWT

6M WD was the most signiﬁcant determinant. The

and ISWD was strongly correlated with the maxi-

regression model for the ISWD was signiﬁcant (r＝mum oxygen uptake,whereas 6MWD was correlat-0.64)and included DLCO (R ＝0.249,p＝0.007),FVC

ed poorly with maximum oxygen uptake .Further-(R ＝0.270,p＝0.011),and FEV /FVC (R ＝0.121,p＝more,our present study showed a larger delta PR in

0.100). This model accounted for 37.1% of thethe ISWT group than in the 6M WT group. This

ISWD,and DLCO was the most signiﬁcant determi-

result suggests that the ISWT is closer to a submax-

nant. The regression model for the total SGRQ

imal exercise test than the 6MWT is,and may be ascore was signiﬁcant (r＝0.62) and included post‑

better indicator of lung function alterations such as

and pre‑modiﬁed BS (R ＝0.272 and ＜0.001, p＝

airﬂow limitation and lung hyperinﬂation. Previous

0.008 and 0.038, respectively), FVC (R ＝0.132, p＝reports also showed a correlation between ISWD

0.036), and FRC (R ＝0.016, p＝0.064). This modeland lung function, such as VC and FEV

accounted for 33.5% of the SGRQ, and dyspnea

correlation between 6MWD and lung function in-during ISWT was the most signiﬁcant determinant.

cluding FVC,FEV ,and TLC .However,Mak VH

Discussion

and noet al and Wijkstra PJ et al reported that 6M WD
was strongly correlated with FVC and FEV

The results of the present study indicate thatand Vagaggini B et al reported that SWD was not

exercise capacity evaluated by ISWD correlated

correlated with FVC, FEV , and TLC . In thesebetter with lung function,but was poorly correlated

studies,the severity of COPD estimated by air ﬂow

with HRQoL. On the other hand, exercise capacity

limitation with each mean FEV ,% of the predicted

62

Shinshu Med J Vol.61

Field walk test in COPD

being 40.3% , 44.3% , and 48% , was more

related with SGRQ activity, impact and total scoresevere than that of our study(63.4%).These resultsin these patients. These results suggest that ISWD

suggest that the correlation between lung functions

is correlated with HRQoL in patients with COPD

and walking distance depends on the severity ofshowing decreased exercise capacity.

COPD. In our study, when restricted to patientswith severe (30%

Limitation

FEV ＜50% predicted) andvery severe (FEV ＜30% predicted)COPD,6M WD

The present study was a retrospective study andwas signiﬁcantly correlated with TLC,IC/TLC andthere was a diﬀerent background in the 2 groups.

DLCO, and SWD was not correlated with FEV .

The results showed that the patients in the 6MWT

However, because the number of patients withgroup showed more lung hyperinﬂation and distur-

severe and very severe COPD was small in our

bed gas exchange when compared with the patients

study,it is diﬃcult to discuss each severity.Further

in the ISWT group and reduction of HROoL esti-

studies which recruit each severitypatients of every

mated by the SGRQ. This is a limitation of theseverity are needed.

present study and it is diﬃcult to compare eachIn the present study, the SGRQ score showed aparameter in the two groups. Therefore, a further

good correlation with 6MWD,as previously report-

prospective study is needed to compare the 6MWTedwith the ISWT.

. The SGRQ is one of the most widely used

questionnaires for assessing HRQoL in COPD

Conclusion

patients and is well known for its validity, repeatability,and sensitivity .On the other hand,theIt was suggested that the 6M WT may be more

6M WT also reﬂects daily activity for most patients

reﬂective of QoL and the ISWT more reﬂective ofwith severely impaired activities,and most patientslung function in patients with COPD. However,

do not achieve maximal exercise capacity during

most of the patients were of mild or moderate

the 6M WT . Because the 6M WT assesses theseverity. Furthermore, the background in thesubmaximal functional exercise capacity,and most

6M WT group and that in the SWT group diﬀered.

of the activities of daily living are performed atFurther prospective studies which recruit eachsubmaximal levels of exertion, the 6M WD should

severity patients of each severity are needed.

correlate well with the SGRQ scores, especially

Acknowledgementswith the scores of the activity domain.
The present study is the ﬁrst to investigate the

The authors wish to thank Dr Koichi Nishimura

correlation between the ISWT and SGRQ. Somefrom the Department of Respiratory Medicine,investigators reported a correlation between the

Rakuwakai Otowa Hospital for permission to use

ISWT and QoL that did not include the SGRQ.

the SGRQ Japanese edition and Dr Hideaki Senju

Mean ISWD was only about 180 m and patients infrom the Graduate School of Biomedical Sciences,these studies had less exercise capacity thanNagasaki University, Unit of Rehabilitation Sci-

patients in our study. In our study, when restricted

ence, Department of Cardiopulmonary Rehabilita-

to patients with severe and verysevere COPD,meantion Science,Japan for permission to use the ISWTISWD was 240 m, and ISWD was signiﬁcantly cor-

Japanese edition.

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（2012.10.29 received ; 2012.12.13 accepted）

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