[Prediction equation of physical activity level based on step counts for Chinese adults: development and validation].

Objective: To develop a prediction equation for estimation physical activity level(PAL) based on the average daily steps in Chinese adults and to verify its prediction power.

Methods: A total of 800 adults with no restriction on physical activity were recruited. Excluding those who wore Actigragh WGT3X-BT accelerometer continuously for less than 3 days, 743 subjects(324 males, 419 females, mean age 31.4 years) were finally included. Daily steps, time of low intensity physical activity(LPA), moderate physical activity(MPA) and vigorous physical activity(VPA) and physical activity energy expenditure(PAEE) were measured by the accelerometer. The method of external validation was adopted. The measured PAL calculated by basal metabolic rate(BMR) measured by indirect thermography(IC) and total energy expenditure(TEE) measured by doubly labeled water method was used as the gold standard. The consistency of the prediction formula was verified by Bland-Altman analysis and the accuracy was verified by the accurate.

Results: The prediction equation was developed: PAL=1.17 + 0.000028 Steps. In the external verification, the mean difference was 0.05, the 95% consistency limit was(-0.26, 0.36), and the accuracy was 73%, indicating a good consistency.

Conclusion: The prediction formula of PAL for Chinese adults based on the steps has good performance and can be applied to the management of physical activity and the prevention of obesity in Chinese adults.