Accelerometry to estimate energy expenditure during activity: best practice with data loggers

Measurement of acceleration can be a proxy for energy expenditure during movement. The variable overall dynamic body acceleration (ODBA), used in recent studies, combines the dynamic elements of acceleration recorded in all three dimensions to measure acceleration and hence energy expenditure due to body movement. However, the simplicity of ODBA affords it limitations. Furthermore, while accelerometry data loggers enable measures to be stored, recording at high frequencies represents a limit to deployment periods as a result of logger memory and/or battery exhaustion. Using bantam chickens walking at different speeds in a respirometer while wearing an accelerometer logger, we investigated the best proxies for rate of oxygen consumption (V_O2) from a range of different models using acceleration. We also investigated the effects of sampling acceleration at different frequencies. The best predictor of was a multiple regression including individual measures of dynamic acceleration in each of the three dimensions. However, R² was relatively high for ODBA as well and also for certain measures of dynamic acceleration in single dimensions. The aforementioned are single variables, therefore easily derived onboard a data logger and from which a simple calibration equation can be derived. For calibrations of V_O2 against ODBA, R² was consistent as sampling number decreased down to 600 samples of each acceleration channel per ODBA data point, beyond which R² tended to be considerably lower. In conclusion, data storage can be maximized when using acceleration as a proxy for V_O2 by consideration of reductions in (1) number of axes measured and (2) sampling frequency.