Metabolic equivalents during the 10-m shuttle walking test for post-myocardial infarction patients

Abstract

Objective: Comorbidities are found to affect metabolic equivalents (METs). Therefore the main objective of this study was to compare METs (1 MET: oxygen uptake (VO 2 ) 3.5 ml/kg/min) during an incremental shuttle walking test (SWT) between non-cardiac and post-myocardial infarction (MI) men, and secondly to determine any differences in VO 2 (ml/kg/min) between flat treadmill walking and the turning during the shuttle walking in non-cardiac subjects. Design: Comparative study. Subjects: Thirty one post-MI (mean (SD) age 63.5 (6.5), range 53-77 years) from phase IV cardiac rehabilitation and 19 non-cardiac (64.6 (7.5), range 51-76 years) men participated. Methods: All subjects performed an SWT, and noncardiac subjects a treadmill test of similar protocol. Throughout both, the subject's VO 2 was measured. Results: Analysis comparing lines of regression showed METs at 1.12 to 4.16 mph were higher (p,0.001) for post-MIs versus non-cardiac subjects. For non-cardiac subjects, there were no differences between the treadmill test and SWT (p.0.9) and LoA showed acceptable agreement in METs between treadmill vs SWT, mean difference 21.1 (8.8) (1.96SD). Conclusion: It would appear that for asymptomatic individuals it is appropriate to apply established METs for flat walking to the SWT. However, the significantly higher METs for the post-MI compared with the non-cardiac subjects indicates the need for caution when using METs derived from healthy subjects in the prescription of exercise for myocardial patients.The health benefits of physical activity for individuals with coronary heart disease (CHD) are well established, 1 and exercise is now a major component of most cardiac rehabilitation programmes. In order for cardiac patients to achieve favourable physical training responses, and enable the appropriate prescription of physical activities, it is important that each patient's functional physical capacity be established. The British Association of Cardiac Rehabilitation advocates the use of the 10-m shuttle walking test (SWT) 2 for this purpose, and commonly the results are used in the ensuing exercise prescription. The SWT involves walking on the flat between two markers 10 m apart, and at the end of each minute the speed increases. Each test stage has been related to a particular metabolic equivalent (1 MET: oxygen uptake (VO 2 ) 3.5 ml/kg/min) 3 so that a participant's functional capacity can easily be established. Metabolic equivalents have been determined for a wide variety of activities and are specific to that particular physical activity. 4 Although MET values were not originally provided with the SWT, 2 the MET values presently used are those obtained from healthy individuals during steady state flat walking.3 Hence they are not specific to the SWT, which involves turning at the end of each 10-m stretch; requirements very different from walking uninterrupted on the flat. Furthermore, although MET values are reasonably stable between most healthy adults, they can be affected by factors such as age, 9 Giv...

The Incremental Shuttle Walk Test in Older Brazilian Adults

“…This difference was statistically significant (p = 0.043). Woolf-May and Ferrett [28] evaluated 19 healthy elderly control subjects and observed similar results (1st ISWT = 553 ± 93 m; 2nd ISWT = 560 ± 111 m). The small number of healthy individuals typically included in control groups precludes the drawing of conclusions regarding the learning effect on the ISWT [18,19,28].…”

“…Woolf-May and Ferrett [28] evaluated 19 healthy elderly control subjects and observed similar results (1st ISWT = 553 ± 93 m; 2nd ISWT = 560 ± 111 m). The small number of healthy individuals typically included in control groups precludes the drawing of conclusions regarding the learning effect on the ISWT [18,19,28]. Although Tully et al [27] applied the ISWT in 106 healthy elderly individuals, the authors did not provide details about the learning effect.…”

“…However, we observed that the intensity of exercise during the ISWT was submaximal (78 ± 12% of HRmax). In studies evaluating healthy individuals [18,19,27,28], we were unable to find details regarding exercise intensity during the ISWT. The results of percentage of HRmax in the present study showed great variability.…”

Can low risk cardiac patients be ‘fast tracked’ to Phase IV community exercise schemes for cardiac rehabilitation? A randomised controlled trial

“…Exercise was prescribed using heart rate ranges using a Karvonen formula obtained from the Incremental Shuttle Walking Test for greater individualization rather than using metabolic equivalents (METS) [21]. However, previous literature utilising the ISWT as a longer term outcome measure within a cardiac rehabilitation population is limited.…”

Evaluating exercise capacity in patients with pulmonary arterial hypertension

“…Even though originally developed for patients with respiratory disease, the SWT has been used in CHF with good reproducibility and accuracy in estimating peak VO 2 [57]. Nevertheless, energy expenditure for the SWT is much higher for patients with heart disease than healthy individuals [58]. Therefore, a combination of gas analysis with the SWT may have a role to play in estimating exercise capacity in patients with PAH.…”