Literature Review: Incremental Shuttle Walk Test (ISWT)
Incremental Shuttle Walk Test (ISWT) has been in use for the last two decades and it is imperative to determine its reliability. Singh, Morgan, Scott, Walters, & Hardman (1992) noted that the ISWT tool could offer an objective means of assessing disability and allowing straightforward comparisons of patients’ activities.
A systematic review of the available literature by many scholars shows that the ISWT was regarded as a reliable test for evaluating maximal exercise capacity in people with chronic respiratory conditions. The ISWT was highly responsive in “pulmonary rehabilitation and bronchodilator use in individuals with chronic obstructive pulmonary disease (COPD), cystic fibrosis and asthma” (Parreira et al., 2014, p. 1357).
On the same note, de Camargo et al. (2014) also established that the ISWT was “reliable, represented functional capacity and induced greater desaturation than cycling” (p. 892).
A study by Jürgensen et al. (2014), test-retest reliability showed results that ranged from good to excellent for the exercise tests with ICC of.90 with a good correlation with the distance covered.
The researchers concluded that the ISWT depicted excellent reliability. As a result, they noted that the ISWT was a possible tool for evaluating clinical conditions and intervention effectiveness, particularly in weight loss and rehabilitative strategies (Jürgensen et al., 2014).
According to Parreira et al. (2014), evaluation of test-retest reliability of the ISWT showed a value of 0.75, which indicated a good reliability based on test results. The intraclass correlation coefficient (ICC) was used to determine the ISWT reliability because it shows variance estimates from analysis of variance and therefore, highlights relationship and differences between two measures (Parreira et al., 2014).
While coefficient of repeatability showed some inconsistencies when used to determine the reliability of various studies, the variation between studies was lower (Bradley, Howard, Wallace, & Elborn, 2000; Fowler, Singh, & Revill, 2005). In this regard, Portney and Watkins note that it is imperative to consider any potential measurement errors within the population of study (as cited in Parreira et al., 2014, p. 1366).
The number of tests conducted also has impacts on the reliability of the ISWT. For instance, several researchers, including Singh et al., Morales et al., Booth and Adams, and Pratt, Fairbank, and Virr noted that there were variations between test 1 and test 2, but such changes were not observed in tests 2 and tests 3 in many of the studies reviewed (as cited in Parreira et al., 2014, p. 1366).
It is imperative to note that these tests were performed on individuals with COPD apart from one test that involved a patient with advanced case of cancer. In addition, Green et al., Lewis et al., Bradley et al. and da Cunha-Filho et al. among other researchers who conducted two tests only did not show significant variations among patients with COPD (as cited in Parreira et al., 2014, p. 1366).
As a result, Parreira et al. (2014) concluded that learning outcomes could have such effects within a given patient population. In other words, the ISWT may be externally paced, but patients with “COPD may decide to finish the test earlier when performing it for the first time because of fear of becoming too dyspneic” (Parreira et al., 2014, p. 1366).
Revill, Morgan, Singh, Williams, and Hardman (1999) examined the repeatability of the endurance shuttle walk test and established that the ESWT was “simple to perform, acceptable to all patients, and exhibited good repeatability after one practice walk” (p. 213). They also noted that patients had significant improvement after rehabilitation.
In addition, the test highlighted increased sensitivity to change relative to the field test of maximal abilities. Revill et al. (1999) also observed that patients did not record any significant changes in their output after a five-week control period before the rehabilitations. After the rehabilitation, however, the ISWT distance increased by 11 percent.
The researchers noted that ESWT could effectively support ISWT and improve its reliability. Other researchers also found out that the ISWT was a reliable measure of cardiorespiratory fitness in patients with coronary heart disease following coronary artery bypass grafts after one practice walk (Fowler, Singh, & Revill, 2005).
Many studies reviewed covered several diseases such as “COPD, chronic heart failure or cardiomyopathy and cystic fibrosis and individuals who underwent vascular or abdominal surgery” (Parreira et al., 2014, p. 1365).
At the same time, there was higher coefficient noted in patients with mild cases of COPD while patients with extremely severe cases of COPD had lower coefficient (Turner, Eastwood, Cecins, Hillman, & Jenkins, 2004; Parreira et al., 2014).
The ISWT, the 6-min walk test (6MWT) and other tests are common when evaluating exercise abilities of patients with chronic lung and heart conditions (Turner et al., 2004). While there were known variations in cases of cardiorespiratory responses in the ISWT and the 6MWT tests, the distance covered in the two tests showed strong correlations.
This suggested a good relationship between the variables measured in the studies. Therefore, the ISWT is an effective tool for monitoring and evaluating treatment changes among patients with chronic lung conditions.
Although the ISWT is a highly reliable test, Parreira et al. (2014) observed that there was limited information regarding its interpretability and generalisation in clinical cases. In fact, only a single study evaluated the minimal clinically important difference (MCID) for the ISWT in a patient with COPD. At the same time, no data existed on the interpretability of the ISWT on other research participants (Parreira et al., 2014).
Dourado, Vidotto, and Guerra, and Jürgensen et al. observed that discrepancies in measures could have originated from the modified values (as cited in Parreira et al., 2014, p. 1367).
In such cases, study participants were allowed to stop once they achieved their maximal effort while other tests allowed participants to stop if they had achieved the 15th level of the test. Many patients who took part in most studies were mainly those with COPD or cardiac diseases (Turner et al., 2004; Parreira et al., 2014, p. 1357). As a result, this composition of patients had ability to influence generalisation of the research outcomes.
It is imperative to note that some studies may not meet quality assessment procedures due to flexibility in interpretation of results. Therefore, reliability and validity of the ISWT may not be absolute. Overall, the ISWT was a reliable and valid tool for providing an objective method of assessing disability and allowing straightforward comparison of patients’ activities.
The incremental shuttle walking test (ISWT) and the 6-min walk test (6MWT)
Given the reliability of field walk tests, tests such as the ISWT and 6MWT have become vital tools for evaluating physical performances of patients during pulmonary rehabilitation (PR) (Turner et al., 2004). Pollentier et al. (2010) conducted a systematic review of studies on the reliability of the 6MWT based on its ability to show functional capacity in patients with chronic heart failure and concluded that the tool had good reliability.
Nasuti, Stuart-Hill and Temple (2013) focused on determining the test–retest reliability of a modified-6MWT. They concluded that the modified 6MWT was simple to use and score and indicated excellent reliability for assessing cardiovascular fitness in adults with intellectual disability (Nasuti et al., 2013).
There are significant differences between the ISWT and the 6MWT. The ISWT is externally paced while the 6MWT is self-paced and may be used continuously or intermittent by considering if the patient takes breaks during the test (Turner et al., 2004). The ISWT needs the patient to increase the speed every minute to the extent that the test may end due to exhaustion or inability to sustain the process.
On this note, one can observe that both tests have dissimilar physiologic information. In addition, the ISWT and 6MWT may work for different groups of patients. For instance, one may need the ISWT because it is incremental in design to test the benefits of a programme based on its ability to evaluate both pre-training and post-training outcomes with regard to exercise intensity.
On the other hand, the 6MWT may be effective when used to evaluate patients with severe cases of COPD because of the self-paced design and the provision for patients to rest during the test (Turner et al., 2004).
Turner at al. (2004) observed patterns in heart rate (HR) and dyspnea when patients were using the 6MWT, which suggested, “patients with COPD titrate exertion against dyspnea to achieve a peak tolerable intensity” (p. 766). This was not “possible with an externally paced ISWT” (Turner at al. 2004, p. 766).
However, the 6MWT relied on “a limited strategy as the patients’ performance converged at increased workloads” (Turner at al. 2004, p. 766). There were peak performance in exercise noted in the ISWT and the 6MWT (Turner at al. 2004, p. 766).
Both the ISWT and 6MWT have shown cases of greater oxygen desaturation during field tests (Turner at al. 2004). This shows that the tests are sensitive in detecting exercise-induced hypoxemia and in evaluating ambulatory oxygen therapy requirements in patients (Turner et al., 2004).
Researchers comparing the ISWT and the 6MWT have observed that peak exercise responses are the same for both tests when patients with moderate to severe COPD participated while patients with mild cases of COPD demonstrated lower peak exercise performances (Turner et al., 2004).
Walking is a familiar, routine activity for patients and therefore, it shows the ability of patients to engage in physically demanding exercises of a daily routine relative to laboratory-controlled walking tests.
While tests have shown similarity in peak HR and dyspnea in the ISWT and the 6MWT tests to show their strenuous nature, they can also offer reliable and valid means of assessing exercise capacity of patients with mild to extremely severe cases of COPD (Turner at al. 2004, p. 766; Dyer, Marriner, Cheema, & Bott, 2011).
Therefore, the ISWT and 6MWT are valid and reliable but are applicable for patients with various exercise needs. In addition, Mainguy et al. (2014) concluded that it remained to be confirmed if the ISWT could be used as an alternative to the 6MWT for patients with pulmonary arterial hypertension (PAH).
The practice walk when undertaking the ISWT
The ISWT has been effective in evaluating exercise capabilities of patients under rehabilitation programmes for various conditions. Moreover, the approach is cost-effective to users. Jolly, Taylor, Lip and Sing (2008) used the Bland Altman limits on the ISWT to determine whether the recommended practice walk was necessary.
They observed an increment in the mean distance after the second walk. As a result, the researchers concluded that there was a need for practice walk when undertaking the ISWT (Jolly et al., 2008).
Generally, it is important for patients to perform practice tests during assessment so that they can attend rehabilitation programmes. Practice tests for the ISWT allow patients to familiarise themselves with the actual ISWT. Turner et al. (2004) observed greater oxygen desaturation during field tests.
This shows that patients should take practice walk for evaluating sensitivity of exercise-induced hypoxemia and assessing ambulatory oxygen therapy needs (Turner et al., 2004).
Dyer et al. (2011) have noted that walking tests are measures for exercise tolerance for patients who need PR. As a result, many physicians have recommended the use of practice walk, but PR care centres often omitted it (Dyer et al., 2011). The researchers showed that such omissions and the absence of practice walk in the ISWT could lead to potential clinical misjudgements (Dyer et al., 2011).
On the other hand, Pepera, McAllister and Sandercock (2010) found out that there were no learning changes in the ISWT when patients were subjected to long test-retest duration.
This showed that a practice walk was not necessary. Greater physiological and psychological differences observed in patients were responsible for the variation in the ISWT tests. Overall, Pepera et al. (2010) concluded that further studies were necessary to determine long-term test-retest reliability of the ISWT.
Several studies have highlighted the long-term reliability and validity of the ISWT in clinically supported situations in various patients under rehabilitation programmes (Pepera et al., 2010; Bradley et al., 2000; de Camargo et al., 2014; Parreira et al., 2014). They have noted good test reliability based on the intraclass correlation coefficient.
While studies have shown the reliability of the ISWT, they have also expressed the need to conduct further studies to determine factors that influence reliability under difference programmes and in long-term duration.
These may require evaluations of factors related to age, body composition, pulmonary function, dyspnea and physical activity in daily life because they are determinants of the distance walked on the ISWT (de Camargo et al., 2014, p. 892).
From the reviewed literature, it can be concluded that the ISWT is a reliable and valid test for evaluating maximal exercise capabilities of patients. At the same time, the tool is responsive when used in patients with certain conditions. Some of the studies indicated stronger correlation in test outcomes.
Several factors, such as the number of tests conducted, the severity of the patient conditions and errors in tests among others could affect the reliability and validity of the tool. In addition, factors related to test-retest effects, particularly when patients failed to performance a practice walk also affected outcomes.
These studies also show that a practice walk is necessary to familiarise patients with the ISWT. Despite these differences in outcomes, the ISWT is a reliable tool for determining exercise prescription and physical activities for patients in rehabilitation programmes.
Both the ISWT and the 6WMT are reliable and valid, but their applications depend on patients’ diseases and severity of their conditions. Overall, researchers showed that further studies were necessary to determine elements that affected reliability, validity and responsiveness of the ISWT, particularly in different patients and in long-term duration.
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