Worker’s Cardiorespiratory Fitness Evaluation Using a 3-min Step Test with Daily Physical Activity Assessments

Abstract

As measuring VO2max in the workplace can be burdensome, the development of time-efficient, safe, and validated cardiorespiratory fitness (CRF) evaluation methods would be effective. Although step tests can be used to estimate VO2max, their validity is not sufficient. Recently, precise physical activity (PA) information has been obtained from sophisticated wearable devices. PURPOSE: We developed a new CRF measurement procedure using a 3-min step test along with daily PA assessments. This study investigated the validity of the new method. METHODS: Our study subjects included 80 Japanese workers (45 men and 35 women, aged 30 to 59 years). We measured our subjects’ VO2max by the Bruce protocol using treadmill exercise and an indirect calorimeter. The subjects completed two types of step test: the Chester step test (CST) for ≥6-min, and the JNIOSH step test (JST). The latter was newly developed by our institute and consists of a 3-min (60, 80, 100 BPMs) stepping exercise followed by a 1-min rest. Daily PA levels were assessed by subjects wearing a 7-day accelerometer, and also a questionnaire which measured three types of workers’ PA levels: during working time, non-working time on workdays, and non-workdays. We performed multiple regression analyses using VO2max as the dependent variable, and age, sex, BMI, heart rates from step tests, time (min) spent in given PA levels from the accelerometer, and scored points on the questionnaire, as the independent variables. RESULTS: The correlation coefficients of the step tests and VO2max were 0.65 (R2 = 0.42) in the CST and 0.64 in the JST (0.41). In addition to age, sex, and BMI, the time spent in vigorous (>6.0 METs) PA and PA intensity points on the questionnaire were observed as significant independent variables (P<0.05). Multiple regression analyses showed that the adjusted R2 increased to 0.73 when age, sex, BMI, heart rates during the JST, time spent in vigorous PA, and the questionnaire’s PA intensity points were included as independent variables. CONCLUSION: Our study suggests that this procedure can potentially be used to assess CRF at workers’ health check-ups when VO2max measurements are not available. Supported by the Industrial Disease Clinical Research Grants from the Ministry of Health, Labour and Welfare, Government of Japan (150903-01).