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Table 1 Analysis of the anterior-posterior (AP) and medial-lateral (ML) center of pressure (COP) fluctuation parameters. Shown are: mean distance (MD), mean velocity (MV), range (RANGE), mean frequency (MFREQ), centroidal frequency (CFREQ), frequency dispersion (FREQD) and 50 % power (P50) frequency. Results show the mean ± S.D. for each COP fluctuation parameter and compare unsupported and FES-assisted sitting in 15 (n = 15) able-bodied individuals

From: Trunk muscle co-activation using functional electrical stimulation modifies center of pressure fluctuations during quiet sitting by increasing trunk stiffness

Measures   Unsupported sitting FES-Assisted sitting Wilcoxon signed-ranks test
MD (mm) AP 0.61 ± 0.26 0.54 ± 0.24  
ML 0.52 ± 0.26 0.46 ± 0.28  
MV (mm/s) AP 2.80 ± 0.41 3.04 ± 0.61 *
ML 2.02 ± 0.54 2.30 ± 0.77  
RANGE (mm) AP 0.40 ± 0.18 0.37 ± 0.14  
ML 0.36 ± 0.23 0.33 ± 0.14  
MFREQ (Hz) AP 0.97 ± 0.30 1.13 ± 0.35 *
ML 0.82 ± 0.22 1.01 ± 0.27 *
CFREQ (Hz) AP 1.72 ± 0.23 1.82 ± 0.25  
ML 1.71 ± 0.19 1.67 ± 0.27  
FREQD (-) AP 0.59 ± 0.05 0.56 ± 0.03 **
ML 0.56 ± 0.05 0.54 ± 0.06  
P50 (Hz) AP 0.50 ± 0.10 0.55 ± 0.13 *
ML 0.48 ± 0.12 0.55 ± 0.14  
  1. *p < 0.05; **p < 0.01