Estimating cardiorespiratory fitness from heart rates both during and after stepping exercise: a validated simple and safe procedure for step tests at worksites.

Step test protocols are typically based on the heart rate (HR) measured either during exercise or during recovery. This study developed a new step test protocol to estimate maximal oxygen consumption ( $$\dot{\text{{V}}}{{\text{O}}}_{\text{2max}}$$ ) based on HRs measured during and after exercise, assessed the criterion validity of the model, and evaluated the protocol’s test–retest reliability. The protocol estimates $$\dot{\text{{V}}}{{\text{O}}}_{\text{2max}}$$ from HR measurements made once a minute during 3 min of step exercise and 2 min of recovery. The model was derived using a group of 118 working adults and cross-validated using a second group of 74 working adults. Furthermore, $$\dot{\text{{V}}}{{\text{O}}}_{\text{2max}}$$ was measured using a conventional treadmill test. While multiple regression analyses were used to develop prediction equations for $$\dot{\text{{V}}}{{\text{O}}}_{\text{2max}}$$ , intraclass correlation coefficients (ICCs) were used to examine test–retest reliability. HRs during and after exercise significantly correlated with the measured $$\dot{\text{{V}}}{{\text{O}}}_{\text{2max}}$$ . The highest correlation (r = − 0.61) was for an HR index that combined values of HRs during and after exercise. A model including age, sex, body mass index, and the HR index accounted for 60% of the variance in measured $$\dot{\text{{V}}}{{\text{O}}}_{\text{2max}}$$ (standard error of the estimate, 4.05 mL kg−1 min−1 or 10.5%). Cross-validation analyses demonstrated good stability of the $$\dot{\text{{V}}}{{\text{O}}}_{\text{2max}}$$ prediction models. The ICC for the HR index was 0.65 (0.53–0.74), indicating fair to good reliability. The HR index, based on a combination of HR measurements during and after stepping exercise, offers a validated $$\dot{\text{{V}}}{{\text{O}}}_{\text{2max}}$$ estimation procedure suitable for use in the workplace.