The effect of anatomical placement and trunk adiposity on the reliability and validity of triaxial accelerometer output during treadmill exercise

Background: Accelerometers are commonly used to quantify physical activity. There is no accordance regarding the most suitable attachment site. This study assessed the reliability and validity of accelerometer output (PAC) from 2 placements. Methods: 26 females (age 20.4 ± 1.3 years, body mass 62.7 ± 6.8 kg) twice performed a 16-minute treadmill protocol comprising 4 stages (4, 5, 8, 10 km·hr-1) and oxygen uptake (VO 2) was calculated. Participants wore an accelerometer at the hip and lower back. Skinfold thickness was measured at 8 sites. Reliability was assessed using coefficients of variation (CVintra). Interactions between placement, velocity and PAC (counts·5s-1) were assessed using analysis of covariance. PAC-VO2 associations were assessed using multiple regression. Results: Hip and back placements returned similar reliability (CVintra = 3.0% and 2.8% respectively). Hip PAC were higher (P < .01) during walking with no differences observed during running. Indices of adiposity were related to hip PAC. Regression revealed hip and back PAC as significant predictors of VO2. Back PAC was the least variable. Hip skinfold thickness explained 15% additional variance in VO2 to PAC with reduced standard error. Conclusion: The lower back is a more suitable accelerometer placement for young, active females during treadmill exercise.