Validity of accelerometry in high-intensity complex movements

Abstract: Abstract Aim The aim of the study was to examine the capability of accelerometers to estimate energy expenditure during high-intensity complex physical activity patterns. Also, to investigate whether placing the monitor on the hip or wrist influenced its prediction ability. Furthermore, the purpose was also to evaluate if there was a significant difference in the aforementioned estimations using data from one axis compared to all three axis combined.     Method A total of 14 subjects, eight men and six women, mean (SD) age of 26, 4 (5,5) years were recruited for the study. The participants performed standardised aerobic exercise while accelerometer data and oxygen uptake was measured simultaneously. Two triaxial accelerometers (Actigraph GT3X) were worn on the hip and wrist during the experiment. Indirect calorimetry, using Oxycon mobile, was chosen as the criterion measure. Validity was determined by comparing accelerometer counts with estimated energy expenditure (EE) in kcal/min, derived from measured oxygen consumption, using bivariate Pearson correlation, linear regression and stepwise regression analyses. Equations were calculated using each participant’s individual regression analyses.   Results The experiment reveals that GT3x presents a moderate correlation (r= 0, 47) for estimating EE from aerobics when worn on the hip and a weak correlation (r = 0.34) when worn on the wrist. However, when combined with the body mass variable, a strong correlation was found between accelerometer data for the hip and EE (r= 0.73). At both positions the vector magnitude (r = 0.47 for the hip and r = 0.34 for the wrist) yielded stronger correlations compared to just using the Y-axis (r = 0.15 for the hip and r= 0.08 for the wrist).     Conclusions In conclusion, this study found that GT3x was not particularly valid for assessing energy expenditure in high intensity complex activities. Wearing the accelerometer on the hip yielded higher correlations compared to wearing it on the wrist. When using the accelerometer for estimations of EE the Vector magnitude is to prefer before the Y-axis solely.