Equivalence of accelerometer data for walking and running: Treadmill versus on land

The aim of this study was to compare equivalence and agreement of physical activity output data collected by a Research Tri-axial accelerometer (R3T) during walking and running on a treadmill versus on land. Fifty healthy volunteers, 35 males (age 21.91.8 years) and 15 females (age 21.60.7 years), underwent a series of tests on a treadmill and on land with the order of testing administered randomly. Each participant walked for 10min at 4kmh-1 and 6kmh-1, and ran at 8kmh-1 and 10kmh-1, with the same accelerometer. Analysis of output data was assessed by two statistical tests: the equivalence test and Bland and Altman method. Mean differences for walking were 41.2129.8 counts per minute and -68.8173.15 counts per minute at 4kmh-1 and kmh-1, respectively. Mean differences for running were 19.1253.20 counts per minute and 38.9270.2 counts per minute at 8kmh-1 and 10kmh-1, respectively. The physical activity output data from the treadmill were higher by an average of 3.5% than the data collected on land. The differences obtained between the treadmill and on land were small and non-significant. The equivalence test showed that output data from the treadmill versus on land were equivalent (P0.05). The Bland and Altman method showed good agreement between the counts obtained on the treadmill and on land (P0.05). In conclusion, physical activity output data were similar as measured by the RT3 accelerometer on a treadmill and on land. The findings suggest that the RT3 may be used in a laboratory and extrapolated to data obtained on land.