# Abstract

 *Purpose*. This is a secondary analysis of previously published data to investigate the effects of electrical muscle stimulation (EMS) on strength of various muscle groups in critically ill patients. *Methods*. One hundred forty-two consecutive patients, with APACHE II score ≥ 13, were randomly assigned to the EMS or the control group. EMS sessions were applied daily on vastus lateralis, vastus medialis, and peroneus longus of both lower extremities. Various muscle groups were evaluated with the Medical Research Council (MRC) scale for muscle strength. Handgrip strength assessment was also employed. *Results*. Twenty four patients in the EMS group and 28 patients in the control group were finally evaluated. EMS patients achieved higher MRC scores than controls (*P* ≤ 0.05) in wrist flexion, hip flexion, knee extension, and ankle dorsiflexion. Collectively, the EMS group performed higher (*P* < 0.01) in the legs and overall. Handgrip strength correlated (*P* ≤ 0.01) with the upper and lower extremities' muscle strength and the overall MRC scores. *Conclusions*. EMS has beneficial effects on the strength of critically ill patients mainly affecting muscle groups stimulated, while it may also affect muscle groups not involved presenting itself as a potential effective means of muscle strength preservation and early mobilization in this patient population. # 3. Results Patient recruitment flow chart, as previously reported \[[17](#)\], is presented in [Figure 1](#). Fifty two patients were finally evaluated, 24 in the EMS group and 28 patients in the control group. Baseline characteristics of all patients in the EMS and control groups have been previously reported \[[17](#)\]. Baseline characteristics of patients finally evaluated in both groups are presented in [Table 1](#). The MRC scores of all the movements of the upper and lower extremities assessed are presented in [Table 2](#). Patients of the EMS group performed statistically higher MRC scores than controls in wrist flexion, hip flexion, knee extension, and ankle dorsiflexion of both sides. No statistical differences were found between the two groups in all other movements. No significant between-group differences were observed for the MRC score of the left and the right arm either, while the MRC scores of the left and right legs were significantly higher in the EMS group. Similar between-group results were found for the total MRC score of the arms (EMS: 28 (26--30); control: 26 (22--30), *P* = 0.16) and the legs (EMS: 29 (26--30); control: 25 (20--28), *P* = 0.01). The overall MRC score was significantly higher in patients assigned to the EMS group in comparison to the control group (58 (51--60) versus 52 (40--58), *P* = 0.04) ([Figure 2](#)). In concern to the baseline characteristics of the subgroup in which handgrip dynamometry was applied (*n* = 21), no difference was found between the control (*n* = 9) and the EMS group (*n* = 12) in gender (males/females, 6/3 versus 10/2, *P* = 0.61), age (65 ± 22 versus 61 ± 14 years, *P* = 0.25), or APACHE II score (19 ± 4 versus 17 ± 4, *P* = 0.46). No difference was observed between the EMS and the control group in handgrip strength either in absolute (21.4 ± 10.8 versus 14.8 ± 10.7 kg, resp., *P* = 0.18) or relative (60.2 ± 27.3% predicted versus 49.1 ± 28.5% predicted, resp., *P* = 0.38) values. A significant difference was found in handgrip strength between patients diagnosed with ICU-AW in comparison to those without an ICU-AW diagnosis (6.6 ± 4.4 versus 23.4 ± 8.9 kg, *P* < 0.01), even when the comparison was adjusted for gender and age (*P* < 0.01). This was also the case when handgrip performance was expressed in relative values (29.0 ± 22.4% predicted versus 66.0 ± 22.2% predicted, *P* < 0.01). In concern to between-sides comparison, patients tended to perform better with the dominant rather than the non-dominant hand (16.2 ± 11.1 versus 14.2 ± 9.9 kg, resp., *P* = 0.09). All patients assessed were right handed, therefore the results were similar for comparison between right and left sides. Three patients performed better with the left hand, and in another 3 patients, there was no difference between hands. The 95% limits of agreement were also calculated and found to range from −7.1 to 10.3 kg. In relation to between-trial comparisons, no difference was observed over the 5 trials performed (1st: 16.1 ± 10.5 kg, 2nd: 16.8 ± 10.8 kg, 3rd: 16.9 ± 11.5 kg, 4th: 16.6 ± 11.0, and 5th: 17.1 ± 11.5 kg, *P* = 0.44). Finally, handgrip strength in absolute values correlated (*P* < 0.01) with the MRC score of upper extremities (*r* = 0.78), lower extremities (*r* = 0.73), and the overall (*r* = 0.79) MRC scores ([Figure 3](#)). The respective correlation coefficients (*P* ≤ 0.01) for handgrip strength in relative values (% predicted) were 0.58, 0.53, and 0.55. <figure> <p><img src="" /></p> <figcaption>Flow chart diagram of the patients admitted to the ICU during the 30-month study period. NMBAs: neuromuscular blocking agents.</figcaption> </figure> <figure> <p><img src="" /></p> <figcaption>Arms, legs, and overall MRC scores (median, interquartile range) for EMS and control groups. \*Significant between-group difference (<em>P</em> < 0.05).</figcaption> </figure> <figure> <p><img src="" /></p> <figcaption>Correlation between handgrip dynamometry performance (in absolute values) and the upper (a), lower (b), and overall (c) MRC scores (<em>P</em> < 0.01).</figcaption> </figure> ::::table-wrap

::: caption
Baseline characteristics of the patients finally evaluated in the EMS
group and the control group (mean ± SD; in medication variables: median
(25th--75th percentiles)).
:::

```
                                     EMS group   Control group   *P*
```

______________________________________________________________________

*n* 24 28\
Age, years 55 ± 20 59 ± 21 0.49
Gender, male/female 19/5 22/6 >0.99
SOFA score on admission 8 ± 3 8 ± 3 0.52
APACHE II score on admission 16 ± 4 19 ± 5 0.03
SAPS III score on admission 55 ± 11 58 ± 14 0.34
Diagnostic category at admission\
Brain injury, *n* (%) 9 (38%) 5 (18%)\
Postsurgical, *n* (%) 7 (29%) 5 (18%)\
Respiratory failure, *n* (%) 0 (0%) 2 (6%) 0.05
Sepsis/septic shock, *n* (%) 1 (4%) 10 (36%)\
Trauma, *n* (%) 5 (21%) 5 (18%)\
Other, *n* (%) 2 (8%) 1 (4%)\
Comorbidities\
Cardiovascular disease, *n* (%) 8 (33%) 13 (46%) 0.50
Diabetes mellitus, *n* (%) 3 (13%) 5 (18%) 0.71
GI disease, *n* (%) 3 (13%) 1 (4%) 0.32
Haematologic disease, *n* (%) 1 (4%) 1 (4%) >0.99
Hepatic disease, *n* (%) 2 (8%) 0 (0%) 0.21
Renal disease, *n* (%) 0 (0%) 6 (21%) 0.03
Respiratory disease, *n* (%) 3 (13%) 9 (32%) 0.18
Other, *n* (%) 2 (8%) 1 (4%) 0.59
None reported, *n* (%) 8 (33%) 8 (29%) 0.95
Sepsis during ICU stay, *n* (%) 16 (67%) 21 (75%) 0.72
Medication\
Sedation, days 5 (2--10) 4 (2--9) 0.85
Aminoglycoside administration, days 0 (0--4) 1 (0--4) 0.18
Corticosteroid administration, days 0 (0--2) 0 (0--2) 0.96
NMBA administration, days 0 (0-0) 0 (0-0) 0.48

EMS: electrical muscle stimulation; SOFA: sequential organ failure
assessment; APACHE: acute physiology and chronic health evaluation;
SAPS: simplified acute physiology; GI: gastrointestinal; NMBA:
neuromuscular blocking agents.:::: ::::table-wrap
::: caption
MRC scores of all the upper and lower extremities' movements (median
(25th--75th percentiles)). *P* values refer to between-group comparisons
for each movement.
:::

```
                              EMS group     Control group   *P*
```

______________________________________________________________________

Left side\
Shoulder abduction 4 (4-5) 4 (4-5) 0.41
Forearm flexion 5 (4-5) 4 (4-5) 0.26
Wrist flexion 5 (5-5) 5 (4-5) 0.03
Hip flexion 4 (4-5) 4 (3--5) 0.05
Knee extension 5 (5-5) 4 (3--5) \<0.01
Ankle dorsiflexion 5 (5-5) 5 (4-5) 0.04
Upper extremities (in total) 14 (12--15) 13 (11--15) 0.16
Lower extremities (in total) 14 (13--15) 12 (10--15) 0.02

Right side\
Shoulder abduction 4 (4-5) 4 (3--5) 0.36
Forearm flexion 5 (4-5) 4 (4-5) 0.19
Wrist flexion 5 (5-5) 5 (3--5) 0.04
Hip flexion 5 (4-5) 4 (3--5) 0.04
Knee extension 5 (5-5) 4 (3--5) \<0.01
Ankle dorsiflexion 5 (4-5) 5 (4-5) 0.07
Upper extremities (in total) 14 (13--15) 13 (10--15) 0.17
Lower extremities (in total) 15 (13--15) 13 (10--14) 0.02

EMS: electrical muscle stimulation.::::


Extracted trial result:
Outcome: knee extension (continuous)
Intervention: electrical muscle stimulation (EMS)
Comparator: control
Intervention group size: 24
Comparator group size: 28
Notes: Only median and interquartile range is given.