Muscle electrical activity, functional mobility level, and handgrip strength in intensive care unit patients: a single-center observational study

Intensive care unit-acquired weakness (ICU-AW) is a consequence of critical illness and is associated with functional limitations. Objective assessment using handgrip strength (HGS) and surface electromyography (sEMG) may support monitoring of early rehabilitation in the ICU. This study aimed to evaluate associations between sEMG parameters, mobility level, and HGS in ICU patients. In this single-center observational study, ICU patients were assessed when they met criteria for early rehabilitation using bilateral sEMG and handgrip strength measurement, then classified into four functional mobility levels. Spearman's rank correlation was used to assess HGS-sEMG associations. The Mann-Whitney U test compared sEMG activity between patients who achieved marching in place and those who remained at lower functional mobility levels. A total of 57 ICU patients were assessed. In men, HGS correlated with biceps brachii, flexor digitorum superficialis, and rectus femoris activity during contraction. No significant HGS-sEMG associations were identified in women, which may be related to the smaller female subgroup and reduced statistical power. Men who achieved marching in place showed higher contraction-phase sEMG values for flexor digitorum superficialis and rectus femoris, possibly reflecting upper-limb-assisted standing and stabilization during verticalization. In women, a difference was observed for rectus femoris activity during contraction on the left side. Combined HGS and sEMG assessment may provide complementary exploratory information on neuromuscular function.