An analytical method for characterizing repetitive motion and postural stress using spectral analysis

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Abstract
The availability of small, inexpensive electrogoniometers has made wrist posture measurement during repetitive manual work practical. Efficient analytical methods, however, are not currently available for quantifying the degree of repetitiveness and the interaction with postural stress. Spectral analysis was investigated as a method for characterizing repetitive wrist motion and postural stress using a simple peg transfer task. Wrist posture was controlled by adjusting the pegboard location and by having subjects reach over an obstruction. Work pace was externally controlled using an auditory signal. Angular wrist flexion/extension and ulnar/radial deviation was recorded using a 60 Hz sample rate. Power spectra were computed by stratifying data segments into individual work elements, divided by break points associated with the task. Peak spectral magnitudes and frequency components corresponded closely with joint displacement amplitudes and repetition rates. Spectrum DC component magnitudes were directly related to sustained wrist postures.