Measuring Adolescent Boys' Physical Activity: Bout Length and the Influence of Accelerometer Epoch Length

Abstract

ObjectivesAccurate, objective measurement is important for understanding adolescents' physical activity (PA) behaviour. When using accelerometry to objectively measure PA, a decision must be made regarding how frequently data is recorded (i.e., epoch length). The purpose of this study was to examine i) PA bout length, and ii) the effect of variations in accelerometer epoch length on PA estimates during physical education (PE) and leisure time in adolescent boys.DesignCross-sectional study.MethodsYear 9 boys (N = 133; mean age ±SD = 14.36±0.48 years) wore accelerometers during two PE lessons, and for a period of seven consecutive days. Data were reintegrated from 1s into longer periods of 2, 5, 10, 30, and 60 seconds. ANOVAs were used to test for differences in PA estimates between epochs in leisure time and PE.ResultsThe mean length of vigorous PA (VPA) bouts was 3.5±2.0 seconds for PE and 2.5±1.7 seconds for leisure time, and mean length of moderate PA (MPA) bouts was 2.3±0.5 seconds for PE and 2.9±0.5 seconds for leisure time. During PE, estimates of MVPA, MPA, and light PA (LPA) increased as epoch increased from 1 second to 60 seconds, while VPA and sedentary behaviour estimates decreased. During leisure time, estimates of all PA intensities decreased as epoch increased from 1 second to 60 seconds, with the exception of sedentary behaviour, which increased as epoch length increased.ConclusionThe context in which PA occurs can influence PA bout length measurement and the effect of variations in epoch length on PA estimates. Researchers measuring PA with accelerometry should be conscious of the possible influence of context on PA estimates.

Systematic review of the relationships between objectively measured physical activity and health indicators in school-aged children and youth

“…For instance, heterogeneity in the application of cut-points to define PA intensities may have contributed to inconsistency in results, as described earlier in relation to LPA (Kwon et al 2011;Carson et al 2013). Similarly, the use of different sampling intervals ("epochs") has historically been dictated by accelerometer capability; however, the use of longer epochs (e.g., 60 s) in some studies is likely to have underestimated the volume of higher intensity PA, particularly in this population where the majority of MVPA occurs in bouts of ≤5 s in duration (Sanders et al 2014). Finally, objective measures of PA cannot accurately quantify some fitness activities (e.g., weight training), and until recently could not measure water-based activities; this may have resulted in an underestimation or overestimation of true effects in the present study.…”

“…Finally, objective measures of PA cannot accurately quantify some fitness activities (e.g., weight training), and until recently could not measure water-based activities; this may have resulted in an underestimation or overestimation of true effects in the present study. To begin to address these limitations, future work should adhere to standardized accelerometry cut-points (Trost et al 2011) or adopt new analytic techniques such as pattern recognition (Freedson et al 2012;Trost et al 2014), and use shorter sampling intervals (Sanders et al 2014).…”

An internet-supported school physical activity intervention in low socioeconomic status communities: results from the Activity and Motivation in Physical Education (AMPED) cluster randomised controlled trial

“…We measured MVPA using 1 s epochs to accurately capture the sporadic PA bouts that occur during PE 27. We used vertical axis data to classify activity intensity using an MVPA cut point of ≥38.27 counts per 1 s (derived from a cut point of ≥574 counts per 15 s28).…”

Can Amateur Football Help Players Meet the Requirements for a Healthy Lifestyle? A Case Study

“…Morgan and Borg [18] found that during prolonged work intervals the rate of RPE change is a responsive indicator of fatigue. They found a linear relationship between perceptual factors and physiological (oxygen uptake and heart rate) or physical (work rate) parameters in their 6-20 scale [20].…”

“…Wearable devices like accelerometers are becoming more and popular to objectively monitor and assess free-living physical activity in all type of individuals (i.e., children, adolescents, adults, elderly, athletes, students...), because they can help overcome many of the limitations of most of the other methods used such as questionnaires or pedometers [17]. Accelerometers can provide objective, time-stamped data of the intensity, frequency and duration of any complete program of physical activity performed without disturbing the individuals who wear those devices because of their small size [18]. To our knowledge, there are no published studies which have used accelerometers to assess the impact of amateur football practice in the players.…”