Journal of Applied Physiology, Vol 53, Issue 3 779-783, Copyright © 1982 by American Physiological Society
A statistical analysis of the spectral moments used in EMG tests of endurance
D. Hary, M. J. Belman, J. Propst and S. Lewis
EMG and bandlimited noise (BLN) signals of comparable spectra were
processed to compute the centroid and median frequencies and the high/low
ratio for different record lengths, signal amplitudes, and noise
bandwidths. The spectral moments of EMG and BLN showed similar statistical
properties, independent of record length and amplitude. The signal-to-noise
ratios of the moments increased with record length. Relatively short
records were sufficient to obtain low coefficients of variations especially
for the centroid, which was the most stable and sensitive to changes in the
underlying spectra. The high/low ratio was the least stable moment. A
change of 10 and 3.9% in the centroid over successive records of overall
duration of 8 and 10 s, respectively, was just sufficient to detect a
spectral shift at the P less than 0.05 level. The equivalent percents for
the high/low ratio were 66 and 32.5, respectively. These thresholds of
significance were related to time constants of equivalent exponential
trends in the spectra used to study fatigue. This relationship makes the
results of the present study applicable to a wide variety of EMG tests of
endurance.
