Table 4.

Linear mixed model for mean MRC of all muscle groups^a from the first postoperative day for a maximum of 14 postoperative days (51 patients, 220 observations)

	Estimate of mean MRC in pointsa (95 % CI)	P value
Intercept	4.10 (3.80 to 4.39)	<0.001
Postoperative day	0.02 (−0.02 to 0.05)	0.40
Control group	Reference	.
NMES group	−0.45 (−0.88 to −0.03)	0.04
Postoperative day × Control group	Reference	.
Postoperative day × NMES group	0.09 (0.03 to 0.14)	0.002

Days of ICU and hospital discharge, where no NMES was applied anymore, were excluded in this model

The linear mixed model for mean MRC in Table 4 reads as follows:

MRC = 4.10 + (0.02 × postoperative day) - (0.45 × NMES group) + (0.09 × postoperative day × NMES group)

0.02 is the slope of MRC time variation in the control group, which is the reference group: for each postoperative day, MRC increases by 0.02 points (95 % CI, −0.02 to 0.05 points) in the control group (P = 0.40)

0.45 represents the lower starting point in the NMES group on the first postoperative day before the NMES intervention began: on the first postoperative day, MRC was about −0.45 points (95 % CI, −0.88 to −0.03 points) lower in the NMES group than in the control group (P = 0.04)

0.09 is the slope of MRC time variation in the NMES group: the slope of MRC time variation is 4.5 times higher than the slope in the control group (P = 0.002)

MRC Medical Research Council, CI confidence interval, NMES neuromuscular electrical stimulation

^aAccording to the MRC scale [33], mean MRC score ranges from a minimum of 0 to a maximum of 5 points