Table 2. Muscle activation during sitting.
| HC (n = 25) | cLBP (n = 18) | U (p) | |
|---|---|---|---|
| Median (IQR) | Median (IQR) | ||
| Start EMG RMS (uV) | 481 (391; 919) | 265 (173; 487) | 106 (<0.01) |
| Start EMG RMS (%RMSmvc) | 19.7 (12.6; 25.2) | 24.2 (18.1; 43.9) | 145 (0.05) |
| Start EMG MDF (Hz) | 101.8 (96.7; 113.9) | 125.9 (117.9;148.4) | 80 (< 0.01) |
| EMG RMS slope (uV/min) | 3.9 (0.9; 10.1)** | 3.5 (0.2; 9.2)** | 201 (0.56) |
| EMG RMS slope (% RMSmvc/min) | 0.13 (0.03; 0.28)** | 0.27 (0.05; 0.51)** | 281 (0.17) |
| EMG MDF slope (Hz/min) | -0.02 (-0.19; 0.19) | -0.06 (-0.29; 0.07) | 189 (0.38) |
Median and interquartile range (IQR) of the low back pain patients (cLBP) and healthy control subjects (HC) of the grid-averaged root mean square amplitude (RMS) and median frequency (MDF) of EMG collected from the lumbar muscles at the start of the sitting task and the slope of the change of these variables during sustained sitting. RMS values are presented both in uV and as a percentage of the maximal RMS obtained under a maximal voluntary contraction (%RMSmvc). U-values and significant levels (p) of the group effect resulting from the Mann-Whitney U test are also included.
** significant different from zero.