The influence of accelerometer epoch length on physical activity output in adolescent athletes.

Epoch in accelerometer measurements is an important option that affects the results of physical activity (PA) analysis. Many studies have been conducted to investigate the effect of epoch on PA output in adolescents, but few have been performed on highly active youth athletes. We aimed to examine the differences in energy expenditure and time spent in different activity intensities by applying various epoch lengths in adolescent athletes. The participants of this study comprised 31 male athletes aged 12 to 13 in basketball, soccer, and taekwondo teams. Athletes wore a tri-axial accelerometer attached to the right hip for 6 to 7 consecutive days, including sleeping time. Subsequently, the recorded data from the accelerometer were downloaded using the ActiLife software and analyzed by varying the epoch to 1, 10, 30, and 60 sec. Daily average metabolic equivalents (METs) increased as the epoch increased (=2.918, =0.037), showing a significant difference between 1 and 60-sec epochs. As epoch length increased, sedentary (0-1.5 METs) (=94.001, =0.000) and high intensity (6 METs and higher) activity time (=3.536, =0.017) decreased, while low (1.5-3 METs) (=173.949, = 0.000), moderate (3-6 METs) (=70.792, =0.000), and moderate-to-vigorous activity (3 METs and higher intensity) (=34.683, =0.000) times increased. Comparing PA among adolescent athletes by varying epoch settings of accelerometers revealed differences in PA levels and time spent in different activity intensities. Future studies should consider the characteristic changes in the PA outputs according to the epoch length in very active adolescent athletes.