Predicting V̇O_2max with an objectively measured physical activity in Japanese men

The present study investigated the use of the accelerometer-determined physical activity (PA) variables as the objective PA variables for estimating V̇O_2max in Japanese adult men. One hundred and twenty-seven Japanese adult men aged from 20 to 69 years were recruited as subjects of the present study. Maximal oxygen uptake (V̇O_2max) was measured with a maximal incremental test on a bicycle ergometer. Daily step counts (SC) and the amount spent in moderate to vigorous PA (MVPA) and vigorous PA (VPA) were measured using accelerometer-based activity monitors worn at the waist for seven consecutive days. The non-exercise models were derived using hierarchical linear regression analysis, and cross-validated using two separate cross-validation procedures. SC, MVPA, and VPA were significantly related to V̇O_2max (partial correlation coefficient r = 0.58, r = 0.42, and r = 0.51, respectively) after adjusting for age. Two models were developed by multiple regression to estimate V̇O_2max using data of age, SC, VPA, and either BMI (the coefficient of determination (R²) = 0.71, standard error of estimate (SEE) = 4.2 ml kg^-1 min^-1), or waist circumference (R² = 0.74, SEE = 3.9 ml kg^-1 min ^-1). All regression models demonstrated a high level of cross-validity supported by the minor shrinkage of R² and increment of SEE in the PRESS procedure, and by small constant errors for subgroups of age, SC, and V̇O_2max: This study demonstrated that combining SC with VPA, but not with MVPA, was useful in predicting V̇O_2max variance and improved the ability of the regression models to accurately predict V̇O_2max.