Comparison between an accelerometer and a three-dimensional motion analysis system for the detection of movement

Area of Science:

• Biomechanics
• Kinesiology
• Clinical Assessment

Background:

• Objective clinical assessment of movement onset is crucial for evaluating motor function.
• Traditional methods may lack precision or be cumbersome.
• Accelerometers offer a potential simple and objective measurement tool.

Purpose of the Study:

• To assess the reliability and concurrent validity of an accelerometer for measuring lower limb motor reaction time.
• To validate accelerometry as a simple method for objective clinical assessment of movement onset.

Main Methods:

• Simultaneous measurement of knee extension onset time using an accelerometer and a 3D VICON motion analysis system.
• Testing involved 12 able-bodied participants responding to an audio cue.

Main Results:

• Both accelerometer and 3D VICON system demonstrated good reliability.
• The accelerometer showed a higher intraclass correlation coefficient (ICC) for reliability (ICC₃,₁=0.739).
• Good agreement was observed between paired measurements (mean ICC=0.774), with average 95% limits of agreement from -56.4 to 72.5 mseconds.

Conclusions:

• Accelerometers provide reliable measurements of movement onset time.
• While agreement with 3D motion analysis is good, the wide limits of agreement suggest caution.
• Absolute timings from accelerometers and 3D systems should not be used interchangeably in clinical settings.