Long-term reliability of the incremental shuttle walking test in clinically stable cardiovascular disease patients
Introduction
Functional capacity is an important predictor of mortality and morbidity in patients with cardiovascular disease (CVD). One aim of cardiac rehabilitation should be to increase functional capacity. However, to verify such changes objectively, there is a need for reliable functional capacity tests that can be carried out by nurses and physiotherapists.
Graded exercise tests aim to provoke a physiological response to continuously increasing incremental exercise levels [1], [2]. The requirements of the cardiorespiratory system are challenged as the intensity increases, and the body's ability to cope with these demands can be investigated to provide an insight into aerobic capacity.
Several cardiorespiratory assessment tests and functional measurements have been developed to determine prognosis, prescribe exercise and assess the efficacy of cardiac rehabilitation. Several walk tests based either on a specific time (2-minute, 5-minute, 6-minute, 9-minute and 12-minute walk test), distance (100 m, half mile, 2 km walk test) or walking speed [self-paced, 6-minute and controlled-paced incremental shuttle walking test (ISWT)] are used to assess the functional capacity of cardiac patients, the effectiveness of a cardiac rehabilitation programme and the prognosis of CVD [3].
The British Association for Cardiac Rehabilitation (BACR) recommends use of the ISWT to assess and monitor functional capacity in patients with chronic heart failure, patients who have experienced a myocardial infarction, and patients who have undergone cardiovascular surgery or pacemaker insertion [4], [5], [6], [7], [8].
The ISWT has been used to track changes in functional capacity during cardiac rehabilitation programmes [8], [9], [10], [11]. These studies typically use a single test at the beginning of rehabilitation and compare the distances walked with a post-rehabilitation test. While the ISWT appears to be able to assess changes in functional capacity in patients with CVD, only short-term (up to 7 days) test–retest reliability of the test has been assessed [9], [12], [13]. Given that cardiac rehabilitation programmes typically last for 6 to 12 weeks, long-term reliability is clearly of great importance.
If the ISWT is to be used to assess changes in functional capacity during cardiac rehabilitation, it is necessary to evaluate its long-term reliability. The primary aim of this study was to assess the test–retest reliability of a modified version of the ISWT over 8 weeks in clinically stable CVD patients.
Section snippets
Methods
Thirty CVD patients (15 males and 15 females; age 55 to 80 years) volunteered to participate in this study. Patients were verbally recruited by instructors prior to two consecutive exercise classes. All patients were defined as clinically stable, according to the BACR criteria [14].
All participants were attending a community-based phase IV cardiac rehabilitation programme at the University of Essex. The programme provides additional phase IV cardiac rehabilitation capacity in the local area,
Results
The mean age of participants was 67 ± 8 years. Most participants (60%) were elective post-revascularisation patients (coronary artery bypass graft or percutaneous transluminal coronary angioplasty), 17% were post-myocardial-infarction patients, and the other patients had stable angina or heart failure. Fifty-three percent of patients were β-blocked, but none of the participants changed their medication from pre-test to post-test (Table 1). Paired-samples t-tests showed that body mass remained
Discussion
Functional capacity patterns of CVD patients are usually established by the end of hospital outpatient (phase III) cardiac rehabilitation, and remain stable during community-based phase IV cardiac rehabilitation [8]. Assessment of functional capacity in CVD patients is important for assessing the effectiveness of exercise interventions and in exercise prescription. The ISWT is an affordable alternative to treadmill testing, but its reliability has only been tested over short test–retest
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