A Novel Step-test Protocol Enabling Individual Measurements With No Special Equipment

The J-NIOSH step test (JST) has been developed and validated in our previous research. Maximal oxygen uptake (VO2max) can be estimated using heart rates (HR) during the JST. However, it requires face-to-face administration by professional and special equipment such as a step board and a monitoring electrocardiograph. PURPOSE: To investigate the reliability and validity of self-administered cardiorespiratory fitness (CRF) assessments with no special equipment to widely popularize CRF as a health index. METHODS: Based on the range of HR changes during the JST, a new test protocol (JST2) consisted of full-body exercises without a step board. JST2 consists of a 3-min 40-sec exercise session with 3 gradually increasing tempos, and a 2-min recovery session. A 10-sec interval for HR recording was provided between each tempo. A total of 136 workers (30-59 years, 49% female) completed anthropometric measurements, validated questionnaire, JST, JST2, and treadmill VO2max test. During both step tests, examiners recorded HR using a monitor electrocardiograph and participants using smartwatches. The data were analyzed in a derivation group of 85 and a validation group of 51. Data from the derivation group were used to develop a VO2max estimation model for JST2 and to analyze the reliability (intraclass correlation coefficient: ICC). Multiple regression analysis was used to derive the model, including sex, age, body mass index, questionnaire score, and HR index of the JST2. Data from the validation group were applied for validity (Bland-Altman plots) analysis. RESULTS: An estimation model of JST2 explained 49% of the variance in VO2max (standard error of the estimate, 4.50 mL/kg/min or 12.2%). The ICCs showed good agreement, with an HR index of 0.92(0.88-0.95) for participant records between 1 week of test and retest and an HR index of 0.91(0.87-0.94) between examiner and participant. In the validation group, a significant correlation was found between measured and estimated (r = 0.64). Bland-Altman results showed no fixed errors (P = 0.19) but indicated systematic errors (r = -0.32, P < 0.05). CONCLUSIONS: Self-administered CRF assessments without special equipment are reliable and can be performed by workers. This new assessment can offer a reliable understanding of a personal health condition.