A step test to estimate cardiorespiratory fitness from heart rates both during and after exercise: A cross-validation study among adolescent university students

National Institute of Occupational Safety and Health, Japan Step Test (JST) is a valid approach for cardiorespiratory fitness assessment among subjects aged 30-60 years. It estimates maximal oxygen uptake (V 4 O 2 max) based on the heart rate (HR) index, a combination of HRs during and after exercise. This study assessed the cross-validity of the V 4 O 2 max estimation using the JST among adolescent university students. A total of 20 healthy male university students were included in this study. Measurements were taken over three days, with cardiopulmonary exercise testing, JST, and the Chester step test (CST) measured on each day. Pearson’s product-rate correlation coefficient or Spearman’s rank-sum correlation coefficient was used for examining the association between measured V 4 O 2 max and estimated V 4 O 2 max and between measured V 4 O 2 max and variables in the JST equation. Bland-Altman analysis was also used to examine the presence and extent of systematic errors between measured and estimated V 4 O 2 max. Estimated V 4 O 2 max by the JST showed a stronger correlation with measured V 4 O 2 max than estimated V 4 O 2 max by the CST. Moreover, the HR index showed the strongest correlation with measured V 4 O 2 max in variables of the JST equation. However, estimated V 4 O 2 max by the JST showed fixed and proportional errors when compared to measured V 4 O 2 max. It was suggested that the HR index, a combination of HRs during and after exercise, was useful for estimating V 4 O 2 max among adolescent university students. Estimated V 4 O 2 max using the JST showed a strong correlation with measured V 4 O 2 max, however, some estimation accuracy prob-lems such as systematic errors. Phys Med,