Normative reference values, determinants and regression equations for the incremental shuttle walk test (ISWT) in healthy Asian population aged 21 to 80 years.

BACKGROUND: The validated Incremental Shuttle Walk Test (ISWT) is widely used for evaluating maximal exercise capacity, with the distance-walked (IWSD) as the primary outcome. However, there are no normative reference values (NRV) and reference equations to predict ISWD for the Singaporean population. OBJECTIVES: This study aims to establish the NRV and reference equations for ISWD in healthy Singaporeans aged 21 to 80 and investigate the determining variables during ISWT. METHODS: This cross-sectional study recruited community-dwelling healthy subjects aged 21-80 from the community via convenience sampling. Each subject completed two trials of the ISWT according to the standard protocol. Variables measured during the trials included ISWD, pre-and post-test heart rate (HR), oxygen saturation, blood pressure (BP), modified Borg's dyspnoea score and Borg's rate of perceived exertion (RPE). RESULTS: 199 healthy Singaporean (females = 114, males = 85) participated in the study. The overall median ISWD was 660.0 metres (m) [interquartile range (IQR):440.0-850.0]. The age-stratified mean ISWD ranged from 430.0 m (IQR:350.0-450.0) (aged 60-80) to 480.0 m (IQR:438.0-650.0) (aged 40-59) to 780.0 m (IQR:670.0-960.0) (aged 21-39). Gender, age, weight, height and HR change (highest post-test HR minus pre-test HR) were the most significant variables (p < 0.001). IWSD (m) = 651.4(Height, m) +89.7(Gender, male = 1; female = 0) -6.31(Age, years) -3.61(Weight, kilograms) +2.54(HR change, beats per minute); R2 = 0.741. Previously published ISWT reference equations cannot accurately predict the ISWD in the Singaporean population. CONCLUSIONS: This study investigated the ISWD NRV and established reference equations for healthy Singaporeans aged 21-80. The information would be beneficial in setting performance benchmarks to guide physical assessment, intervention and rehabilitation.