Incremental shuttle walk test: Reference values and predictive equation for healthy Indian adults

Purpose: Physical inactivity in Indians is leading to an increase in noncommunicable disorders at an early age in life. Early identification and quantification of the lack of physical activity using simple and reliable exercise testing is the need of the hour. The incremental shuttle walk test (ISWT) is an externally paced walk test widely used for the evaluation of exercise capacity. Currently the normative values available for clinical reference are generated from Western populations. Hence, the study was conducted to find normative values for the ISWT in healthy Indian adults (17-75 years). Materials and Methods: A convenience sample of 862 subjects was recruited after ethical approval was obtained. All subjects were divided into groups as per age and gender. For age, the grouping was as follows: Group 1: Young adulthood (17-40 years), group 2: Middle adulthood (40-65 years), and group 3: Old adulthood (>65 years). The ISWT was performed as per standard protocol by Sally Singh. Results: The average distance walked were 709.2m, 556.4m and 441.3m in females and 807.9 m, 639.6 m and 478.2 m in males in the three respective age groups. Stepwise regression analysis revealed age and gender as key variables correlating with incremental shuttle walk distance (ISWD). The derived predictive equations for males and females may be given as follows: 740.351 - (5.676 x age) + (99.007 x gender). Conclusion: Reference values were generated for healthy Indian adults. Physiological response to the ISWT was shown to be affected by gender and increasing age. Easily measurable variables explained 68% of the variance seen in the test, making the reference equation a relevant part of the evaluation of the ISWT.