A wireless accelerometer node for reliable and valid measurement of lumbar accelerations during treadmill running

Abstract

This study investigated the reliability of a wireless accelerometer and its agreement with optical motion capture for the measurement of root mean square (RMS) acceleration during running. RMS acceleration provides a whole-body metric of movement mechanics and economy. Fifteen healthy college-age participants performed treadmill running for two 60-s trials at 2.22, 2.78, and 3.33 m/s and one trial of 150 s (five 30-s epochs) at 2.78 m/s. We assessed between-trial and within-trial reliability, and agreement in each axis between a trunk-mounted wireless accelerometer and a reflective marker on the accelerometer measured by optical motion capture. Intraclass correlations assessing between-trial repeatability were 0.89–0.97, depending on the axis, and intraclass correlations assessing within-trial repeatability were 0.99–1.00. Bland–Altman analyses assessing agreement indicated mean difference values between −0.03 and 0.03 g, depending on the axis. Anterio-posterior acceleration had the greatest limits of agreement (LOA) (±0.12 g) and vertical acceleration had the smallest LOA (±0.03 g). For measuring RMS acceleration of the trunk, this wireless accelerometer node provides repeatable and valid measurement compared with the standard laboratory method of optical motion capture.

Keywords:

• Optical motion capture
• root mean square
• agreement

Acknowledgements

The authors are thankful to the participants and for data collection assistance from Ann Brennan, Ken Hayes, Zachary Maino, Aaron Stickel, and Lucas Wall. No funding was received for this study.

Notes

1. We indicate an addition of 1 g to correct for gravity because the convention for the vertical axis is positive for up and negative for down. Moe-Nilssen (1998a) indicates a subtraction of 1 g to correct for gravity using the same axis convention, which we believe to be an oversight in that paper.