Predictors of shuttle walking test performance in patients with cardiovascular disease

Abstract

ObjectiveThe incremental shuttle walking test (ISWT) is used to estimate cardiorespiratory fitness, but data from healthy individuals suggest that demographic and anthropometric measures account for much of the variance in test performance. The aim of this study was to determine whether anthropometric, demographic and selected gait measures also predict ISWT performance (i.e. distance walked) in patients with cardiovascular disease. DesignObservational study. SettingA community-based cardiac rehabilitation centre (Cohort 1) and a hospital outpatient cardiac rehabilitation programme (Cohort 2). ParticipantsSixteen patients with clinically stable cardiovascular disease (Cohort 1) and 113 patients undergoing cardiac rehabilitation (Cohort 2). InterventionsPatients in Cohort 1 performed the ISWT on two occasions. Anthropometric data and walking and turning variables were collected. Linear regression analyses were used to identify the predictors of test performance. The authors subsequently attempted to validate the equation created by comparing predicted and actual ISWT values in a larger (n=113) validation sample (Cohort 2). Main outcome measuresDistance walked during ISWT, step length and height. ResultsNo gait or turning measures were significantly associated with ISWT performance. Distance walked correlated most strongly with step length (r=0.83, P<0.05) and height (r=0.74, P<0.05). Given the similarity of these correlations and the rarity of step length assessment in clinical practice, ISWT performance was predicted using patient's height; this explained 55% of the variance in ISWT performance. Height was also the best predictor in Cohort 2, explaining 17% of test variance (P<0.01). Body mass index explained an additional 3% of variance (P<0.05) in ISWT performance. ConclusionsRoutine clinical measures, particularly patient's height, are predictive of ISWT performance. The findings of the present study are in partial agreement with similar studies performed in healthy individuals, and it remains unclear whether the ISWT performance of patients with cardiovascular disease is influenced by the same factors as the ISWT performance of healthy individuals.