A Multi-Level Analysis of the Effects of Epoch Length on the Estimates of Children’s Moderate to Vigorous Physical Activity

Abstract

Using an ActiGraph GT3X+ accelerometer, the study examined the effects of different epoch lengths on children’s moderate to vigorous physical activity (MVPA). The study also tested how different MVPA levels influence the relationship between epoch length and MVPA. The participants included third (n = 28) and fourth grade (n = 35) students. The third graders participated in a physical education class while the fourth graders were engaged in an active video game (AVG) class. Data were downloaded using six different epoch lengths. MVPA estimates were determined by five different cut points. Multi-level analyses were used to analyze the data. Results showed that when lower cut points were used, MVPA was positively related to epoch lengths, and this relationship was stronger when the MVPA level was higher. When higher cut points were used, epoch length was negatively related to MVPA, and this relationship was stronger when the MVPA level was lower. This study revealed that different epoch lengths generate various estimates of MVPA, and the relationship between epoch length and MVPA is affected by MVPA levels.