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VALIDITY AND RELIABILITY
OF THE INCREMENTAL
SHUTTLE WALK TEST AND
SIX-MINUTE WALK TEST IN
CHRONIC HEART FAILURE
*PhD Student, Glasgow Caledonian University, Glasgow /
Cardiac Rehabilitation Physiotherapist, NHS Ayrshire & Arran
(aynsley.cowie@aaaht.scot.nhs.uk) TITLE OF PRESENTATION
Mr John SmithSchools and Colleges Liaison
Cowie, A.*, Thow, M.K.,
Granat, M., Mitchell, S.L.
Background Valid - measures what it’s supposed to measure
Reliable - gives consistent results repeatedly
PeakVO2 (peak oxygen uptake) from cardiopulmonary exercise test
(CPET) = most accurate measure of exercise capacity
(gold standard)
CPET: incremental cycling / treadmill protocol to symptom-limited
peak BUT time-consuming, costly, and often poorly tolerated
(clinically inaccessible)
Incremental Shuttle Walk Test (ISWT) and self-paced 6-minute Walk
Test (6MWT) = popular clinical substitutes; simplistic, inexpensive,
familiar
6MWT (Butland et al, 1982)
self-paced over known distance for
6 minutes (with rests as required)
many trials in CHF* inconsistently
confirming validity and reliability
* = chronic heart failure
ISWT (Singh et al, 1992)
externally-paced, progressive
walking speed (around cones)
governed by audio signal
less evidence to support use -
very few trials in CHF
Trials comparing tests in CHF:
ISWT more valid
Reliability confirmed though lack
of consensus regards pre-test
familiarisation / practice walk?
(Green et al, 2001; Morales et al, 1999;
Pulz et al, 2008)
10m
Background
To examine:
Validity of the ISWT and 6MWT (in relation to
symptom-limited treadmill CPET)
Test-retest reliability of each walking test
Whether familiarisation has any effect on walking
test reliability
Aims
Power calculation: n=22 (80% power) (Green et al, 2001)
Recruited from CHF nurses, and cardiology clinics
EXCLUSION CRITERIA
Contraindications to exercise
testing (ACSM, 2006)
Local NHS Ayrshire & Arran
treadmill testing protocol
(exclusions) adhered to
INCLUSION CRITERIA
Left ventricular dysfunction
Clinically stable for at least
one month (ACPICR, 2006)
Optimised cardiac
medication doses
Sample
n=22 familiarised with either
ISWT or 6MWT (randomly assigned)
1 x treadmill CPET, STEEP protocol (Northridge et al, 1990)
3 x ISWT and 3 x 6MWT (familiarised test first)
Data from 1st
walking test
compared to data
from CPET
Data over 3
attempts of each
walking test
examined
Reliability data of those
familiarised compared
to those not
VALIDITY OF EACH
WALKING TEST
RELIABILITY OF EACH
WALKING TEST
EFFECT OF
FAMILIARISATION
ON RELIABILITY
OUTCOMES:
peakVO2 (ml.kg-1.min-1)
walking test distance (m) Methodology
Cosmed K4b2
27 participants
recruited initially
n=22 completed
study with no
adverse events
Results
CHARACTERISTICS VALUES
n n=22
Mean age (years) 64 Age
range (years) 51-76 Gender
(males / females) 19 / 3
NYHA class: II / III 13 / 9
Aetiology of heart failure:
- idiopathic 0
- ischaemic 14
- other 8
Baseline ECG:
sinus rhythm / atrial fibrillation 17 / 5
Validity
Neither walking
test stressed
participants to the
level of CPET
Mean peakVO2*:
CPET - 16.99
ISWT - 13.43
6MWT - 14.39
(* = ml.kg-1.min-1)
6MWTISWTCPET
25
20
15
10
Pe
akV
O2
(m
l.kg
-1.m
in-1
)
CPET PeakVO2 Versus
Walking Test PeakVO2
6MWT distance has stronger relationship with CPET
peakVO2 - though both relationships significant (p<0.05)
**regression correlation, †closer to 1.0 = stronger relationship
Validity
COMPARISON** r VALUE† p VALUE
6MWT distance v. CPET pVO2 r = 0.62 p = 0.001
ISWT distance v. CPET pVO2 r = 0.48 p = 0.001
CPET PeakVO2 Versus
Walking Test Distance
*Two-way ANOVA
†intra-class correlation
co-efficient (closer to 1.0
= stronger relationship)
Reliability & Familiarisation
ICC† (p VALUE)
ALL PARTICIPANTS THOSE FAMILIARISED
6MWT 0.74 (p=0.97) 0.58 (p=0.45)
ISWT 0.84 (p=0.15) 0.86 (p=0.29)
ISWT showed better reliability - enhanced by
familiarisation
Reliability of 6MWT reduced with familiarisation
All reliability analyses non-significant (p>0.05)
WALKING
TEST
PeakVO2 Data Over 3 Attempts of Each Walking Test
Neither walking test stressed participants to the level of CPET
6MWT distance is a more valid representation of exercise
capacity than ISWT distance
ISWT demonstrated greater reliability - and reliability improved
with familiarisation
Familiarisation increased variation in 6MWT data, reducing its
reliability
As reliability is a pre-condition of validity, the ISWT may be the
more valid test for clinical practice in CHF
Conclusions
American College of Sports Medicine, 2006. Guidelines for exercise testing and
prescription. 7th Edition. Baltimore, Maryland: Lippincott Williams & Wilkins;
Association of Chartered Physiotherapists in Cardiac Rehabilitation (2006)
Standards for the exercise component of the phase III cardiac rehabilitation.
London: ACPICR.
Butland, R.J., Pang, J. & Gross, E.R. (1982) Two-, Six- and 12-minute Walking Tests
in Respiratory Disease. BMJ, 284,1607-8.
Green, D., Watts, K., Rankin, S., Wong, P. & O’Driscoll, J., 2001. A Comparison of
the Shuttle and 6-Minute Walking Tests with Peak Oxygen Consumption in
Heart Failure. Journal of Science and Medicine in Sport, 4(3),292-300.
References
Morales, F.J., Martinez, A., Mendez, M., Agarrado, A., Ortega, F., Fernandez
Guerra, J. et al (1999) A Shuttle Walk Test for Assessment of Functional Capacity
in Chronic Heart Failure. American Heart Journal, 138,291-8.
Northridge, D., Grant, S., Ford, I., Christie, J., McLenachan, J., Connelly, D. et al.
1990. Novel Exercise Protocol Suitable for Use on a Treadmill or a Bicycle
Ergometer. British Heart Journal, 64,313-316.
Pulz C, Diniz RV, Tebexreni AS. Incremental shuttle and six-minute walking tests
in the assessment of functional capacity in chronic heart failure. Canadian
Journal of Cardiology 2008;24:131-5.
Singh, S.J., Morgan, M.D.L., Scott, S., Walters, D., & Hardman, A.E., 1992.
Development of a Shuttle Walking Test of Disability in Patients with Chronic
Airways Obstruction. Thorax, 1019-24.
References
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